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Dissertations / Theses on the topic 'Phytopathogen'

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Published: 4 June 2021
Last updated: 15 June 2024

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1

Peng, Xiaowen. "Total synthesis of the phytopathogen (+)-fomannosin." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1155158634.

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2

Forizs, Laetitia. "Metabolism and pathogenicity in the phytopathogen Rhodococcus fascians." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209742.

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Rhodococcus fascians is a Gram-positive phytopathogenic bacterium which induces the development of leafy galls, local amplifications of multiple buds, on most infected plants. This process is linked to the production of phytohormones along with the presence of essential virulence-associated genes like the plasmid loci att and fas and the chromosomal gene vicA. However, the presence of these genes is not sufficient to ensure the infection phenotype development, indicating that other genes play a role in R. fascians pathogenicity. In this work, we studied the metabolic modifications occurring when the bacterium interacts with its host using a proteomic approach. A comparison between virulent and avirulent strains showed variations in the expression of catalases. In the virulent strain, besides the transitory induction of the att locus expression, the bacterium changes its metabolism from the Krebs cycle to the glyoxylate shunt, a process which is frequently observed in bacteria confronted to a hostile environment. The expression of the shunt-specific enzyme isocitrate lyase increased, while expression of fumarate hydratase and pyruvate dehydrogenase decreased. Hence, we focused on the link between the glyoxylate shunt and virulence. A screening of a R. fascians mutant library based on the capacity of bacteria to use acetate as the sole carbon source, a metabolic pathway depending on the glyoxylate shunt, resulted in the identification of a new gene essential for R. fascians pathogenicity. This gene encodes a glycosyl transferase, an enzyme known to be involved in the bacterial cell wall biosynthesis but possibly also implicated in cytokinin secretion. A mutant in this gene harboured an altered colony phenotype and could not induce malformations on infected plants. Accordingly, our results were integrated in the leafy gall pathology model recently presented by Stes et al. (2011). Finally, the several questions that are raised by this work, allowed us to suggest further research perspectives in order to unveil a little more of the R. fascians mysterious ways to interact with the plant./Rhodococcus fascians est une bactérie Gram-positive phytopathogène qui induit le développement de galles feuillées, des amplifications locales de multiples bourgeons, sur la plupart des plantes infectées. Ce processus est lié à la production de phytohormones ainsi qu’à la présence de gènes essentiels associés à la virulence tels que les loci plasmidiques att et fas et le gène chromosomique vicA. Cependant, la présence de ces gènes ne suffit pas à garantir le développement du phénotype d’infection, indiquant que d’autres gènes jouent un rôle dans la pathogénicité de R. fascians. Dans ce travail, nous avons étudié les modifications métaboliques qui se produisent lorsque la bactérie interagit avec son hôte par une approche protéomique. Une comparaison entre les souches virulente et avirulente a mis en évidence des variations d’expression au niveau des catalases. Dans la souche virulente, outre l’induction transitoire de l’expression du locus att, la bactérie change son métabolisme pour passer du cycle de Krebs au shunt du glyoxylate, un processus fréquemment observé chez les bactéries confrontées à un environnement hostile. L’expression de l’isocitrate lyase, enzyme spécifique au shunt, augmente, tandis que celle de la fumarate hydratase et de la pyruvate déhydrogénase diminue. Nous nous sommes donc intéressés au lien entre le shunt du glyoxylate et la virulence. Le screening d’une banque de mutants de R. fascians basé sur la capacité de la bactérie à utiliser l’acétate comme seule source de carbone, une voie métabolique dépendant du shunt du glyoxylate, a permis d’identifier un nouveau gène essentiel pour la pathogénicité de R. fascians. Ce gène code pour une glycosyl transferase, une enzyme impliquée dans la biosynthèse de la paroi bactérienne mais également dans la sécrétion des cytokinines. Un mutant dans ce gène présente un phénotype de colonie altéré et ne peut induire de malformations chez les plantes infectées. Finalement, nos résultats et les pistes d’interprétations que nous avons émisent nous permettent de compléter le modèle de l’interaction R. fascians-plante proposé récemment par Stes et al. (2011). Des perspectives de recherches visant une meilleure compréhension de ce pathosystème sont proposées.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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3

Calassanzio, Matteo <1989&gt. "Studies of sustainable strategies to control phytopathogen agents." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9411/1/PhD%20Thesis%20Calassanzio%20Matteo.pdf.

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Choosing natural enemies to suppress pest population has been for a long the key of biological control. Overtime the term biological control has also been applied to the use of suppressive soils, bio-disinfection and biopesticides. Biological control agents (BCA) and natural compounds, extracted or fermented from various sources, are the resources for containing phytopathogens. BCA can act through direct antagonism mechanisms or inducing hypovirulence of the pathogen. The first part of the thesis focused on mycoviruses infecting phytopathogenic fungi belonging to the genus Fusarium. The development of new approaches capable of faster dissecting the virome of filamentous fungi samples was performed. The semiconductor-based sequencer Ion Torrent™ and the nanopore-based sequencer MinION have been exploited to analyze DNA and RNA referable to viral genomes. Comparison with GeneBank accessions and sequence analysis allowed to identify more than 40 putative viral species, some of these mycovirus genera have been studied as inducers of hypovirulence in several phytopathogenic fungi, therefore future works will focus on the comparison of the morphology and physiology of the fungal strain infected and cured by the viruses identified and their possible use as a biocontrol agent. In a second part of the thesis the potential of botanical pesticides has been evaluated for the biocontrol of phloem limited phytopathogens such as phytoplasmas. The only active compounds able to control phytoplasmas are the antibiotic oxytetracyclines and in vitro direct and fast screening of new antimicrobials compounds on media is almost impossible due to the difficulty to culture phytoplasmas. For this reason, a simple and reliable screening method was developed to evaluate the effects of antimicrobials directly on phytoplasmas by an “ex-vivo” approach. Using scanning electron microscopy (SEM) in parallel with molecular tools (ddRT-PCR), the direct activity of tetracyclines on phytoplasma cells was verified, identifying also a promising compound showing similar activity.
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4

Mobbs, Daniel James. "Studies towards the control of the phytopathogen Botrytis cinerea." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297945.

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5

Chibi, Nancy. "Molecular and phenotypic characterisation of the phytopathogen 'Pseudomonas syringae' pv. 'tabaci'." Thesis, Royal Holloway, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409299.

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6

Monson, Rita Elaine. "Regulation of quorum sensing in the phytopathogen Erwinia carotovora subsp. atroseptica." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611200.

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7

Barenstrauch, Margot. "Characterization of oxylipin signaling in the chemical interaction between the endophyte Paraconiothyrium variabile and the phytopathogen Fusarium oxysporum." Thesis, Paris, Muséum national d'histoire naturelle, 2018. http://www.theses.fr/2018MNHN0010/document.

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Les champignons endophytes sont des microorganismes non-pathogènes impliqués dans des associations mutualistes avec les plantes. Les endophytes foliaires, en particulier, représentent un groupe très divers, mais leurs interactions avec la plante hôte et ses micro-organismes associés sont peu connues. Des travaux préliminaires initiés par notre équipe, explorant la diversité microbienne foliaire du conifère Cephalotaxus harringtonia, ont permis d’isoler la souche fongique Paraconiothyrium variabile (Ascomycota), un antagoniste du phytopathogène Fusarium oxysporum. Au cours de leur interaction, on détecte des quantités moindres de beauvéricine, une mycotoxine synthétisée par F. oxysporum. En parallèle, on observe une augmentation de la synthèse de deux oxylipines, l’acide 13-hydroperoxyoctadécadiénoïque (13-HPODE) et l’acide 13-oxo-octadécadiénoïque (13-oxo-ODE), dans la zone de confrontation. L'objectif de ce travail était de comprendre les mécanismes conduisant à la diminution de la beauvéricine au cours de l'interaction et d'explorer le rôle des oxylipines dans la régulation de cette dernière. Dans mon travail de thèse, je montre la présence de deux gènes lox chez P. variabile (pvlox1 et pvlox2) codant tous deux pour des manganèse lipoxygénases, potentiellement à l'origine des acides 13-HPODE et 13-oxo-ODE. Pvlox2 est spécifiquement induit pendant l'interaction, et ces résultats sont corroborés par une synthèse accrue de 13-HPODE chez P. variabile. Par ailleurs, l'interaction avec l’endophyte, ainsi que l'ajout de l’oxylipine 13-HPODE, régulent positivement la voie de biosynthèse de la beauvéricine, comme l’indiquent les teneurs plus élevées en mycotoxines observées chez F. oxysporum. Enfin, nous avons montré que la beauvéricine inhibait la croissance de l’endophyte, mais que ce dernier était capable de dégrader la mycotoxine, expliquant ainsi les faibles quantités de beauvericine observées initialement dans la zone de compétition. Ce travail contribue à la compréhension du rôle des oxylipines dans la communication inter-microbienne
Endophytic fungi are non-pathogenic microorganisms involved in mutualistic associations with their host. Foliar endophytes, in particular, represent a very diverse group but little is known about their interactions with the host and its associated micro-organisms. In preliminary work, exploring the leaf microbial diversity of the conifer Cephalotaxus harringtonia, our team isolated the fungal strain Paraconiothyrium variabile (Ascomycota), an antagonist of the phytopathogen Fusarium oxysporum. During their interaction, decreased amounts of the F. oxysporum mycotoxin beauvericin, and higher amounts of the two oxylipins, 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-oxo-octadecadienoic acid (13-oxo-ODE), were observed in the confrontation zone. The objective of the present work was to understand the mechanisms leading to beauvericin decrease during the interaction and to explore the role of oxylipins in beauvericin regulation. In my thesis work I show the presence of two lox genes in P. variabile (pvlox1 and pvlox2) coding both for manganese lipoxygenases, potentially at the origin of 13-HPODE and 13-oxo-ODE. Pvlox2 is specifically induced during the interaction, which lead to an increased synthesis of 13-HPODE in P. variabile. The endophyte itself, as well as the oxylipin 13-HPODE, up-regulated the beauvericin biosynthesis gene beas, which was paralleled by higher mycotoxin content in the mycelium of F. oxysporum. Finally, we showed that beauvericin inhibited the endophyte’s growth, but the latter was capable to degrade the mycotoxin, which explains the lower amounts of beauvericin found in the competition zone. This work presents pioneer undertaking to elucidate the role of oxylipins in inter-microbial crosstalk
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8

Fisher, Emily Jane Dangl J. L. "Identification of virulence factors in the phytopathogen P. syringae by molecular evolution." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1812.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2008.
Title from electronic title page (viewed Dec. 11, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology." Discipline: Biology; Department/School: Biology.
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9

Massa, Claudia. "Structural and Functional Studies of a Polygalacturonase from the Phytopathogen Burkholderia cepacia." Doctoral thesis, SISSA, 2006. http://hdl.handle.net/20.500.11767/4012.

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10

Brual, Typhaine. "Unraveling virulence regulation in pectinolytic bacteria : Insights from ArcZ and RsmC." Electronic Thesis or Diss., Lyon, INSA, 2023. http://www.theses.fr/2023ISAL0100.

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Les bactéries pectinolytiques du genre Dickeya prospèrent dans diverses niches écologiques, y compris l'eau, le sol et les plantes, s'adaptant à des environnements complexes et en constante évolution, façonnés par diverses interactions biotiques et abiotiques.Dans cette thèse, nous avons étudié les mécanismes qui régulent la virulence du genre Dickeya, en particulier D. dadantii et D. solani.Nos principaux résultats concernent la régulation post-transcriptionnelle exercée par le sRNA ArcZ et la régulation post-traductionnelle modulée par la protéine RsmC. ArcZ est un acteur clé de l'adaptation de D. solani, régulant la motilité en fonction des conditions environnementales et favorisant la virulence lors de l'infection des plantes. En outre, ArcZ joue un rôle essentiel dans la résistance à l’acidité.RsmC, quant à lui, est impliqué dans la régulation de la motilité et joue un rôle complexe dans la virulence. Nos résultats suggèrent de nouvelles interactions pour RsmC et ouvrent des perspectives pour l'étude d'autres fonctions non documentées.En un mot, notre étude révèle comment des régulateurs tels que ArcZ et RsmC orchestrent les réponses bactériennes à un environnement dynamique. Ces résultats mettent en évidence l'adaptabilité des espèces du genre Dickeya et soulignent l'importance du contexte écologique dans l'étude du comportement bactérien
Pectinolytic bacteria of the genus Dickeya thrive in diverse ecological niches including water, soil and plants, adapting to complex and ever-changing environments shaped by various biotic and abiotic interactions. In this thesis, we investigated the mechanisms that regulate the virulence of the genus Dickeya, in particular D. dadantii and D. solani. Our main findings concern post-transcriptional regulation exerted by the sRNA ArcZ and post-translational regulation modulated by the protein RsmC. ArcZ is a key player in D. solani adaptation, regulating motility according to environmental conditions and enhancing virulence during plant infection. In addition, ArcZ plays a critical role in acid resistance. RsmC, in turn, is involved in the regulation of motility and has a complex role in virulence. Our results suggest novel interactions for RsmC and open perspectives for studying other undocumented functions. In a word, our study reveals how regulators such as ArcZ and RsmC orchestrate bacterial responses to a dynamic environment. These findings highlight the adaptability of Dickeya species and underscore the importance of ecological context in the study of bacterial behavior
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11

Hutchens, Andrew R. "Ambient pH- and carbon-regulated gene expression in the necrotrophic phytopathogen Sclerotinia sclerotiorum." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011843.

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12

Day, Andrew. "Environmental bacteriophages infecting Dickeya and Serratia species : receptors and diversity." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290114.

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Phytopathogenic Dickeya species inflict large economic losses on a variety of crops. A lack of effective chemical control methods has generated interest in the use of bacteriophages (phages) as a novel tool for biocontrol. In the last decade, six phages have been isolated in Belgium and Poland using Dickeya solani as the host. Previous work in this laboratory has isolated ninety phages capable of infecting D. solani. The majority have been morphologically classified as members of the Ackermannviridae family. In agreement with findings in Salmonella and Klebsiella species, the capsule of D. solani is a likely receptor of Ackermannviridae family phages. Analysis of D. solani strains carrying reporter fusions suggested that the capsule genes are expressed in response to nutritional stress, however disruption of the capsular polysaccharide cluster did not significantly impact virulence. Experiments assessing capsular polysaccharide as a putative receptor for Ackermannviridae family phages in nosocomial pathogen Serratia produced inconclusive results. Phageresistance due to random transposon mutagenesis identified genes encoding transcription factors and regulators, but none directly linked to capsular polysaccharide production. Thirteen phages were capable of infecting a wider host range of Dickeya species. Morphological and genomic analysis showed that six were Podoviridae family members, whilst the other seven were Myoviridae family members. These are part of the recently defined 'hairy Myoviridae', characterised by a distinct morphology. Another member of this grouping was isolated during this study, but is more closely related to phages of Erwinia amylovora. A subset of the Ackermannviridae family phages were shown to be capable of facilitating transduction. This makes them unsuitable for use in the environment due to the risk of deleterious horizontal gene transfer. This is also true for the Myoviridae family members, but not for one of the Podoviridae family members. This phage could therefore be a promising candidate for therapeutic use.
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Ayriss, Joanne Elizabeth. "Analysis of putative thiamine biosynthetic genes from the phytopathogen Mycosphaerella graminicola for fungicide target validation." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271866.

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14

Taylor, Neil Gavin. "Isolation of antibody fragments recognising phytopathogen secreted enzymes and the expression of scFvs in transgenic tobacco." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/29767.

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The expression of antibody fragments has been suggested as a possible mechanism for the introduction of disease resistance into transgenic plants. Important pathogenicity factors of certain phytopathogens are secreted cell wall degrading enzymes. Pectate lyases and polygalacturonase are important cell wall degrading enzymes secreted by Erwinia carotovora and Botrytis cinerea respectively. The blocking of activities of these enzymes could offer an opportunity for reducing the ingress of these pathogens. Pectate lyase C from E. carotovara was purified to near homogeneity by cation exchange chromatography following overexpression in E.coli. Hybridoma lines recognising this enzyme were obtained and an scFv (single chain variable fragment) isolated from one of these lines. This scFv did not recognise pectate lyase.;The purified enzyme was used to inoculate mice to construct libraries of scFvs derived from spleen mRNA. These libraries did not yield any scFvs recognising pectate lyase. A synthetic human scFv library was then screened with pectate lyase and Botrytis cinerea polygalacturonase (PG), and scFvs recognising PG isolated. These scFvs were tested against a range of antigens to determine specificity. One scFv, C1, was found to bind PG but did not bind to control antigens bovine serum antigen, hen egg lysozyme or pectate lyase. Neither did this scFv bind to PG isolated from another fungal pathogen, Cryphonectria parasistica. scFv C1 was found to bind to a carbohydrate epitope on the B. cinerea polygalacturonase.
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15

Newman, Mari-Anne. "Interaction of plants with the phytopathogen Xanthomonas campestris : the role of specific bacterial products in triggering plant defences." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262457.

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16

Le, Thi Thu Giang [Verfasser]. "Characterization of transcription factors important for fatty acid and lipid metabolism in the phytopathogen Fusarium graminearum / Thi Thu Giang Le." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2011. http://d-nb.info/1237051223/34.

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17

Zaghouani, Mehdi. "Synthèse totale, révision structurale et histoire naturelle des cytochalasines de petite taille : les périconiasines." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066492/document.

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Les cytochalasines, métabolites secondaires issus de PKS-NRPS fongiques, représentent une large famille de composés bioactifs intéressants de par leur système tricyclique. Ce document expose les stratégies de synthèse vers l’obtention de cytochalasines de petite taille, les périconiasines A-C, isolées de Periconia sp. F-31, qui partagent un système 9/6/5 et des cytotoxicités intéressantes envers l’adénocarcinome du colon, et la synthèse totale de la périconiasine G qui possède le plus petit macrocycle rencontré jusqu’à présent dans cette famille avec un système 7/6/5. Plusieurs analogues du produit naturel dont l’bis-iso-périconiasine C qui se caractérise par une isomérisation des alcènes initiaux sont décrits, ainsi que leurs tests sur des cellules HeLa et MDA ce qui a permis l’identification d’un composé hautement cytotoxique. D’autre part, la synthèse totale de la périconiasine G a conduit à réviser la structure initialement attribuée par Dai et al. et réaliser des tests biologiques pertinents sur les bactéries gram-négatives Micrococcus luteus et Staphylococcus aureus ainsi que sur le phytopathogène Botrytis cinerea responsable de la « pourriture grise » des cultures à travers le monde. Une spécificité de la périconiasine G contre le phytopathogène a pu être découverte ce qui amène à considérer le rôle protecteur des endophytes dans le mutualisme plante-champignon
Cytochalasins are secondary metabolites born from fungal PKS-NRPS which possess a characteristic tricyclic core and display a large variety of biological properties. This document exposes the strategies elaborated toward total syntheses of small cytochalasins periconiasins A-C, isolated from Periconia sp. F-31 and sharing a 9/6/5 backbone, and periconiasin G which possesses the smallest macrocyclic ring so far in this family with a 7/6/5 tricyclic ring. Several analogues of natural product periconiasin C, including isomer bis-iso-périconiasin C, are described, as well as their bioassays on HeLa and MDA cell lines which allowed identification of a highly toxic lead. Moreover, the total synthesis of periconiasin G led us to the revise the structure published by Dai et al. and carry out pertinent bioassays on gram-positives bacteria Micrococcus luteus and Staphylococcus aureus, and on the phytopathogen Botrytis cinerea responsible of the gray mold disease throughout the world. A specificity of periconiasin G against the phytopathogen was discovered, leading us to consider the protective role of endophytes in the plant-fungus mutualism
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Deblais, Loic. "Understanding of Salmonella-phytopathogen-environment-plant interactions and development of novel antimicrobial to reduce the Salmonella burden in fresh tomato production." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534437638478448.

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Solé, Castellví Montserrat. "Functional characterization of AWR affector proteins from the phytopathogen "R. solanacearum" (Caracterització funcional de les proteïnes efectores AWR del fitopatogen "R. solanacearum")." Doctoral thesis, Universitat de Barcelona, 2011. http://hdl.handle.net/10803/83902.

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"R. solanacearum" is a devastating bacterial pathogen that infects "Solanaceae" spp. such as tomato, eggplant or banana. A functional T3SS is required for virulence and more than 70 putative effectors have been described, although only few have been studied. This thesis focuses on a five-member gene family of effectors named "awr". We demonstrated that awr gene family is extremely conserved among R. solanacearum strains but also present in other plant pathogens such as Acidovorax or Burkholderia spp. and even present in the human pathogen B. pseudomallei. Virulence of a Ralstonia mutant strain devoid of all awr genes was tested on tomato, eggplant and Aradidopsis. Plant growth of quintuple mutant strain was considerably reduced in natural hosts, indicating a role in virulence, but remained unchanged in Arabidopsis. Col-0 infection with Pseudomonas syringae DC3000 heterologously expressing each AWR was also performed. While presence of some AWRs in Pseudomonas did not have an effect on plant growth, others (like AWR5) dramatically reduced the pathogen multiplication, pointing out a possible plant detection. In order to unravel the functions of AWR proteins, they were transiently expressed by means of Agrobacterium in non-host Nicotiana spp. Upon AWR expression, necroses took place to different extents on the plant leaves. AWR5 induced the strongest necrosis, resembling an HR phenotype which was later confirmed by TB/DAB staining and by RT-PCR of specific HR marker genes. Furthermore, a strong reduction in yeast cells was experimented upon several AWR protein expressions which indicate that the mechanisms that might be altered by these effector proteins is conserved among eukaryotes and hence reinforces their role in virulence. AWR4 appeared not to be toxic in this model organism and for that reason we sought to decipher some of the plant targets of this AWR protein as a start point. Out of more than 60 interacting clones were sequenced after a yeast-two hybrid screening with Arabidopsis root cDNA from R. solanacearum challenged plants. Among them, several defense-related proteins were found: phenylalanine ammonia-lyase, MPK6, DMR6 or KIN10. In order to find other key genes for AWR activity, the AWRs that displayed a strong yeast toxicity were heterologously produced in both E. coli and R. solanacearum to be ready to be employed as a bait for plant protein complexes that will be analysed by mass spectrometry. In summary, AWR are highly conserved effectors that play an important role in both pathogenesis and plant recognition as they reduce P. syringae virulence and trigger an HR-like phenotype in non-host plants. Deciphering effector function will open promising avenues towards the design of new strategies to control R. solanacearum.
R. solanacearum és un patogen bacterià capaç d’infectar diferents solanàcies com ara la tomaquera, la patatera, l’alberginiera o el plataner. Aquest fitopatogen injecta més de 70 proteïnes efectores en la cèl•lula vegetal hoste, tot i que només algunes han sigut ja estudiades. Aquesta tesi es centra en una família multigènica d’efectors: els AWRs. Els estudis científics duts a terme durant aquesta tesi van demostrar que la família de AWR no només estava altament conservada en el llinatge de R. solanacearum sinó que també es trobava present en altres fitopatògens o inclús en el patogen humà Burkholderia pseudomallei. A més a més, diferents assajos de patogenicitat en tomaquera i alberginiera van provar que els gens awr presentaven un paper clar en virulència per aquests hostes. Contràriament, la presència d’aquestes proteïnes en la planta model Arabidopsis thaliana produïen una disminució en la capacitat infectiva/multiplicativa. Això indicaria una dualitat dels efectors AWR depenent del context que ens trobem, ja sigui contribuint a la patogenicitat del bacteri o bé éssent reconeguts per la planta i així disminuint la patogenicitat bacteriana. Per tal de desentranyar les funcions de les proteïnes AWR, es van expressar de forma transitòria a la planta model no-hoste Nicotiana spp. L’expressió d’algunes proteïnes AWR va provocar una forta necrosi de les fulles que s’assemblaria a una resposta hipersensible. Mitjançant diferents tincions i assajos de PCR en temps real es va corroborar que l’AWR5 presentava aquest tipus de mort cel•lular programada. L’elevada toxicitat d’algunes AWRs es va demostrar també en llevat. En el transcurs d’aquesta tesi també s’ha realitzat un crivellatge en doble híbrid per tal de buscar proteïnes dianes de la planta per a l’AWR4 (la menys tòxica). A més a més, es va posar a punt l’expressió dels AWRs a E. coli o bé a R. solanacearum per tal d’abordar altres tècniques que permetin una millor cerca d’interactors en el futur.
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Aruscavage, Daniel. "Effect of bacterial phytopathogen damage on the survival and proliferation of Escherichia coli O157 in the phyllosphere of lettuce and tomato plants." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1186675048.

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Aruscavage, Daniel. "Effect of bacterial phytopathogen damage on the survival and proliferation of Escherichia coli 0157 in the phyllosphere of lettuce and tomato plants." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1186675048.

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22

Tsui, Sarina. "Estudo de elementos transponíveis em Puccinia psidii Winter, agente causal de ferrugem em Eucalyptus spp." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-13112015-173221/.

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A cultura do eucalipto apresenta grande importância no setor florestal no mundo. No Brasil, 70% da área florestal plantada é destinada ao eucalipto. Entretanto, a ferrugem das mirtáceas, também conhecida como ferrugem do eucalipto, causada pelo fungo Puccinia psidii Winter, afeta o enorme potencial produtivo das plantações de eucalipto. A biologia, mecanismos de patogenicidade e genética desse patógeno são pouco conhecidos, apesar de sua importância para o setor florestal. Os elementos transponíveis (TEs) são sequências de DNA com a capacidade de migrar e influenciar a organização, integridade e evolução do genoma hospedeiro. O presente trabalho teve como principal objetivo estudar os TEs presentes no genoma de P. psidii, combinando ferramentas in silico e moleculares. A classificação dos elementos transponíveis no genoma de P. psidii MF-1 foi realizada utilizando contigs previamente minerados e remontados, bem como sem seleção prévia dos contigs, por meio do programa RepeatMasker. Ambas estratégias apontaram o predomínio de elementos da Classe I - LTR Retrotransposons no genoma de P. psidii MF-1. O resultado condiz com a composição de TEs em fungos fitopatogênicos descrita na literatura. Algumas análises in silico, como verificação de integridade e anotação manual de sequências proteicas foram também realizadas para alguns contigs classificados como TEs. Assim, foi possível observar a presença de sequências conservadas pertencentes à região pol em LTR Retrotransposons. Além disso, as análises permitiram inferir sobre a existência de TEs híbridos no genoma parcialmente sequenciado de P. psidii MF-1. Paralelamente foi também realizada uma análise comparativa entre os TEs presentes nos genomas de P. graminis, P. striiformis, P. triticina e P. psidii. Observou-se que P. graminis, P. striiformis e P. triticina apresentam maior frequência de elementos da Classe II, do tipo DNA Transposons ao contrário de P. psidii, com maior frequência de elementos da Classe I. Interessantemente, a quantidade de elementos desconhecidos foi similarmente alta para todos os quatro genomas avaliados. Este tipo de análise é muito importante, pois evidencia a grande quantidade de famílias de TEs novas a serem descobertas. Elas podem estar potencialmente relacionadas ao silenciamento de genes importantes à virulência destes patógenos. A utilização de TEs no estudo de diversidade genética entre populações é bastante comum. A técnica molecular IRAP foi utilizada para acessar a diversidade entre populações de P. psidii originárias de três híbridos de Eucalyptus spp., goiabeira, jambeiro e jabuticabeira. No entanto, esta técnica não se mostrou eficiente para detectar polimorfismos existentes entre estas populações. A anotação de TEs foi difícil devido à observação de sequências de elementos sobrepostas, o que podem representar híbridos de TEs, entretanto, visando a confirmação desta hipótese por meio da PCR, alguns contigs serão sequenciados e mais estudos devem ser realizados para a continuação desta confirmação. Os resultados apresentados neste trabalho são inéditos e representam uma etapa crucial no entendimento de TEs em fungos do gênero Puccinia, em especial do patógeno P. psidii para o desenvolvimento de melhores mecanismos de controle de ferrugem.
The culture of eucalyptus has great importance worldwide in forestry sector. In Brazil, 70% of cultivated forest area is intended for Eucalyptus. However, the eucalyptus potential productive has been affected by rust disease, caused by the fungus Puccinia psidii Winter. Despite its importance to brazilian and world forest sector, the knowledge of biology, genetic and pathogenic mechanisms of this pathogen is scarce. Transposable elements (TEs) are mobile DNA fragments that influence the organization and development of the host genome. These elements have the ability to move within host genome, and their insertion can cause a wide spectrum of mutations in their hosts. This study aims to decipher the TEs in P. psidii genome by combining in silico and molecular tools. P. psidii MF-1 TEs classification was performed automatically, through RepeatMasker software, being observed a predominance of Class I - LTR Retrotransposons in P. psidii MF-1 genome. This result is consistent with the TEs composition described in phytopathogenic fungi. Some in silico analysis, as integrity and manual annotation of conserved protein sequences from TEs were carried out with P. psidii MF-1 contigs classified as transposable elements. The presence of conserved sequences belonging to pol region in LTR Retrotransposons was observed. Furthermore, these analysis allowed the inference of hybrid TEs in P. psidii MF-1. At the same time, a comparative analysis of TEs present in other Puccinia genomes and P. psidii MF-1 was also performed. The P. graminis, P. striiformis and P. triticina genomes have higher frequency of Class II - DNA Transposons unlike the results found for P. psidii. Interestingly, the number of unknown elements was similarly high for all genomes. This type of analysis is very importante because it shows a great number of potential new TEs families to be discovered. They may be potentially related to the virulence gene silencing of these pathogens. Using TEs for study the fungal genetic diversity is quite common. The IRAP technique was used to access the diversity among P. psidii populations originated from three Eucalyptus spp. hybrids, guava, syzigium and jabuticaba. However, this technique was not efficient to detect existing polymorphisms between these populations. TEs annotation was labored due to the existence of overlapping elements, which may represent hybrids TEs. PCR tool was used to confirm some sequences annotated as hybrids and more studies are needed to confirm this hyphotesis. The results presented in this study are novel and is a crucial step in understanding the genetic of P. psidii pathogen for further improvements of rust control mechanisms.
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23

Bartholomew, Holly Packard. "In planta studies of the corn pathogen Pantoea stewartii subsp. stewartii and applications of a corn-based industrial byproduct." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99356.

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Corn is a valuable agricultural commodity in the United States and in the world. The causal agent of Stewart's wilt disease in corn, Pantoea stewartii subsp. stewartii, is a bacterial phytopathogen that is vectored into the plant by the corn flea beetle, Chaetocnema pulicaria. After entering the apoplast of the leaf, the bacteria cause water soaking symptoms before traveling to the plant xylem to form a dense biofilm, thereby blocking water transport and inducing necrosis and wilt. This results in reduced crop yield and may even lead to death of the corn plant. To better understand the in planta requirements of this pathogen, a whole transcriptome study was performed via RNA-Seq to determine genes differentially expressed in the bacteria while inside the corn. It was found that nutrient transporters and stress response genes were upregulated specifically when the bacteria are in their host plant, suggesting a response to nutrient availability and host defense in the xylem. Further elucidation of the genes required for the P. stewartii in planta lifestyle was performed via a reverse genetics approach where in-frame gene deletions and the corresponding complementation strains were constructed for genes that had shown a fitness defect in corn based on a previously published Tn-Seq study: genes encoding seven transcription factors, nsrR, iscR, lrp, nac, DSJ_00125, DSJ_03645, and DSJ_18135, as well as a hypothetical protein DSJ_21690. Investigation of the physiological role of these genes was performed using in planta virulence and competition assays for all strains. An in planta qRT-PCR analysis of bacterial gene transcription was also completed for the strains with deletions in nsrR and iscR. In vitro assays were performed on all strains to determine their capsule production and motility phenotypes. Taken together, it was seen that iscR is important for colonization capabilities in planta, both NsrR and IscR act as regulators, and lrp is important for full disease capabilities, perhaps due to reduced capsule and motility phenotypes. These findings lay the groundwork for finding potential disease intervention strategies not only against P. stewartii, but also other xylem-dwelling bacterial phytopathogens. In addition to exploring ways to enhance crop yield, an additional research area was on repurposing a byproduct of corn ethanol production, syrup. It was hypothesized that this corn-based syrup could be utilized as a carbon source to grown bacteria. In turn, the resulting bacterial biomass could then be added as a fish feed supplement in aquaculture. Syrup was tested as a growth medium for individual soil bacterial isolates as well as a full mixed bacterial community consortium to determine which bacteria could grow most efficiently, both in rate and yield. It was found that the highest growth rate and yield was from Bacillus species, some of which may have probiotic benefits to fish. Ultimately, the collective outcomes from these projects in basic research about a bacterial corn pathogen and applied research about beneficial microbes grown on a corn-based substrate are expected to improve scientific endeavors as well as agricultural practices.
Doctor of Philosophy
Corn is a top agricultural commodity in the United States, as a food for human consumption, a primary nutrient source used in animal feed, and a substrate consumed during biofuel production. These various corn-based industries are impacted by bacteria in multiple ways; in some cases, bacteria may cause disease that reduces crop yield, but other bacteria serve beneficial roles that enhance health. This dissertation research describes studies about the bacterium that causes Stewart's wilt disease in corn, Panteoa stewartii subsp. stewartii. In an initial experiment, the genes that P. stewartii expresses at the highest levels when it grows inside the corn plant were identified. These genes were deduced to be important for the ability of the bacterium to live successfully in this environment. This work was followed up with a more specific approach that examined the role of certain genes that were predicted to be master regulators of the expression of other genes in the ability of the P. stewartii to colonize the plant and/or cause disease. By identifying key bacterial genes, disease intervention strategies to combat Stewart's wilt and other similar bacterial plant pathogen diseases might become possible. Protecting corn yields is important for ethanol production. The final study of this dissertation examined the ability of bacteria to grow on a byproduct of ethanol production called syrup. The goal was to then use the biomass of these beneficial microbes as a food source for animals being produced in aquaculture facilities. Among the species tested, the highest growth rate and yield was from Bacillus subtilis, a safe-to-eat bacterium that has known beneficial health properties when consumed by fish. Overall, the research studies that were completed for this dissertation have the potential to improve agricultural practices by decreasing corn disease leading to increased corn yield and developing new downstream corn-based animal feed products.
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Ramachandran, Revathy. "Investigation of the quorum-sensing regulon in the corn pathogen Pantoea stewartii." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/56840.

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Pantoea stewartii subsp. stewartii is a bacterium that causes Stewart’s wilt disease in corn plants. The bacteria are transmitted to the plants via an insect vector, the corn flea beetle Chaetocnema pulicaria. Once in the plant, the bacteria migrate to the xylem and grow to high cell densities, forming a biofilm by secreting excess capsular exopolysaccharide, which blocks water transport and causes wilting. The timing of virulence factor synthesis is regulated by the cell-density dependent quorum sensing (QS) system. Such temporal regulation is crucial in establishing infection and is orchestrated by the QS-dependent transcriptional regulator EsaR. EsaR represses expression of capsular exopolysaccharide at low cell densities. At high cell densities, an acylated homoserine lactone (AHL) molecule produced during growth by the cognate AHL-synthase EsaI accumulates. The AHL binds to and inactivates EsaR, causing derepression of capsule production. EsaR is a member of the LuxR family of QS-dependent transcriptional factors. Most LuxR homologs are unstable and/or insoluble in the absence of AHL which has hindered structural studies. Chapter Two describes the changes in the structure of EsaR due to binding of AHL ligand as determined through biochemical methods. EsaR was found to be stable and retain its multimeric state in the absence or presence of AHL, but intra- and inter-domain changes occurred that affect its DNA-binding capacity. Apart from repressing expression of capsule at low cell-densities, EsaR represses its own expression and activates production of a small RNA, EsaS, with unknown function. In Chapter Three a proteomic approach was used to identify an additional 30 QS-controlled proteins. Genes encoding three of these proteins are directly regulated by EsaR and the EsaR binding sites in the respective promoters were defined. In Chapter Four, a high-throughput RNA-Seq method identified even more genes in the QS regulon that the proteomic approach overlooked. RNA-Seq analysis of rRNA-depleted RNA from two strains of P. stewartii was used as a screen to help identify 11 promoters, subsequently shown to be directly regulated by EsaR in vitro. Most of the genes controlled by QS grouped into three major physiological responses, capsule & cell wall production, surface motility & adhesion and stress response. In Chapter Five, the role of two QS regulated genes, dkgA (encoding 2, 5-diketo-D-gluconate) and lrhA (encoding a repressor of chemotaxis, adhesion and motility), in plant virulence were examined. These studies have better characterized the QS regulator EsaR and its interaction with the AHL ligand, and shown that QS has a more global response in P. stewartii than previously recognized. Further characterization of the genes identified in this study could facilitate identification of factors crucial in plant pathogenesis or insect-vector symbiosis and aid in the development of molecular-based approaches for possible disease intervention.
Ph. D.
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25

FONTANA, Riccardo. "APPROCCI NATURALI CONTRO I BATTERI FITOPATOGENI - SOSTANZE NATURALI E BATTERIOFAGI COME STRUMENTO CONTRO LE MALATTIE DELLE PIANTE." Doctoral thesis, Università degli studi di Ferrara, 2023. https://hdl.handle.net/11392/2504898.

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Le malattie infettive delle piante sono causate da microrganismi patogeni, insetti e piante parassitarie. Con lo sviluppo dell'agricoltura, le malattie infettive sono diventate un fattore sempre più significativo che influenza la resa delle colture e, quindi, l'efficienza economica. A causa del significativo impatto di queste malattie sulla salute umana e animale, e sull'economia, lo sviluppo di una piattaforma per gestire e minimizzare le perdite causate da parassiti delle piante sembra urgente.La perdita di efficacia dei trattamenti chimici dovuta allo sviluppo della resistenza ai microbicidi, e la presa di coscienza circa il loro impatto ambientale, sono alcune delle ragioni per le quali è necessario sviluppare nuove strategie. Molti pesticidi chimici sono stati ritirati dal mercato a causa di severe normative UE, e, inoltre, i residui di pesticidi, compresi i loro metaboliti e prodotti di degradazione, rimangono nelle piante o nel suolo, il che diventa una fonte significativa di contaminazione per le colture e l'ambiente. Per questo motivo, le politiche "verdi" mirano a combattere l'uso di prodotti chimici al fine di evitare rischi per la salute umana e animale e per l'ambiente e mirano a sviluppare prodotti ad alto valore aggiunto derivati da un'agricoltura biologica, il cui uso contribuisce alla conservazione della biodiversità perché, non utilizzando pesticidi sintetici chimici, protegge le specie e aiuta nel ripristino degli ecosistemi terrestri e acquatici. In questo contesto, la ricerca di prodotti alternativi ad alta efficienza, a basso costo e a basso impatto ambientale rappresenta una vera sfida per un'agricoltura più sostenibile. La ricerca di alternative all'uso di inquinanti/antibiotici ha portato allo studio di fitocomplessi con proprietà antimicrobiche, in quanto le piante rappresentano una ricca fonte di composti bioattivi, potendo produrre un'ampia varietà di composti chimici, quali terpeni, terpenoidi, saponine, glucosinolati, isotiocianati, alcaloidi e polifenoli. Allo stesso tempo, è stata incoraggiata la lotta biologica contro i fitopatogeni. Anche i batteriofagi, virus dei batteri, possono rappresentare un nuovo strumento per avvicinarsi a queste malattie. Lo scopo di questo progetto è quello di studiare composti antimicrobici di derivazione naturale e batteriofagi isolati da campioni ambientali come soluzione “green" per la gestione delle malattie delle piante e/o come induttori naturali del sistema di difesa della pianta ospite.Tutti i fitocomplessi utilizzati nello studio sono stati estratti dalla Moringa oleifera e Magnolia officinalis, e hanno dimostrato proprietà batteriostatiche e battericide. Tutti i composti rilevati mostrano effetti sull'inibizione nei processi di formazione del biofilm e portano a una significativa alterazione della permeabilità della membrana batterica. Si ipotizza che l'effetto sia effettuato su diversi livelli: i fenoli sono infatti in grado di alterare la permeabilità della membrana portando ad un arresto della sintesi dell'ATP, con conseguente rallentamento di tutte le funzioni dipendenti dall'ATP. La modifica dell'integrità e permeabilità della membrana comporta una notevole dissipazione di energia in quanto comporta la dissipazione del potenziale d'azione e l'alterazione del gradiente elettrochimico, condizioni necessarie per la sintesi dell'ATP. Questo altera vari meccanismi dipendenti dall'ATP, come la formazione di biofilm: in questo modo, Xanthomonas, Erwinia e Pseudomonas sottoposti a queste carenze di energia, sono inibiti nella loro produzione di biofilm e quindi nella loro patogenicità. Questo approccio potrebbe potenzialmente migliorare la sostenibilità dell'agricoltura, la sicurezza alimentare per gli agricoltori rurali e, d'altra parte, semplificare i test in serra o sul campo. Infine, le richieste di registrazione di nuovi prodotti fitosanitari aumenterebbero la competitività dell'Italia sui mercati comunitari e mondiali.
Infectious plant diseases are caused by pathogenic microorganisms as well as insects and parasitic plants. With the development of agriculture, infectious plant diseases have become an increasingly significant factor affecting crop yield and economic efficiency. Due to the significant impact of plant diseases on human and animal health, and on the economy, the development of a platform to eradicate, manage, minimize the losses caused by plant pests, seems urgent. The loss of effectiveness of chemical treatments due to the development of resistance to microbicides and the environmental impact, are some of the reasons for which new control strategies need to be developed. Many chemical pesticides have been withdrawn from the market due to strict EU regulations. In addition, pesticide residues, including their metabolites and degradation products, remain in plants or soil, which becomes a significant source of contamination for crops and the environment. For this reason, "Green" policies aim to combat the use of agrochemicals in order to avoid risks to human and animal health and the environment and aim to develop high value-added products derived from or an organic agriculture, the use of which contributes to the conservation of biodiversity because, by not using chemical synthetic pesticides, it protects species and restores terrestrial and aquatic ecosystems. In this context, the search for alternative products with high efficiency, low cost, and low environmental impact represents a real challenge for more sustainable agriculture. The search for alternatives to the use of pollutants or antibiotics has led to the study of phytocomplexes with antimicrobial properties, as plants represent a rich source of bioactive compounds, being able to produce a wide variety of chemical compounds, such as terpenes, terpenoids, saponins, glucosinolates, isothiocyanates, alkaloids and polyphenolic compounds. At the same time, the biological fight against phytopathogens has been encouraged. Apart from Bacillus spp. or Trichoderma spp., also bacteriophages may represent a new tool for approaching these diseases. The aim of this project is therefore to study natural antimicrobial compounds and bacteriophages isolated from environmental sample as a “green solution” for plant diseases management and/or as natural inducers of the host plant defense system.. All the phytocomplexes used in the study were extracted from Moringa oleifera (MO) and Magnolia officinalis, and have shown both bacteriostatic and bactericidal properties. All the compounds detected in MOEs extracts display effects on inhibition in biofilm formation processes and lead to a significant alteration of the bacterial membrane. It’s assumed that the effect is carried out at several levels: phenols are in fact capable of altering the permeability of the membrane leading to a halt in the ATP-synthesis, resulting in slowing down of all ATP-dependent functions. The modification of membrane integrity and permeability results in a considerable energy dissipation as it involves the dissipation of the action potential and the alteration of the electrochemical gradient, necessary conditions for the synthesis of ATP. This alters various ATP-dependent mechanisms, such as biofilm formation: in this way, Xanthomonas, Erwinia and Pseudomonas subjected to these energy shortages, are inhibited in their biofilm production and therefore in their pathogenicity. This approach could potentially improve agriculture sustainability, food security for rural farmers and, on the other hand, simplify greenhouse or field testing. Finally, the registration requests for new plant protection products would increase Italy's competitiveness in the Community and world markets.
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Bourras, Salim Ahmed. "Pathogenomics of the fungal phytopathogen Leptosphaeria maculans : exploitation of a large T-DNA mutagenized collection to elucidate T-DNA integration patterns and identify new pathogenicity determinants." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112072.

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Leptosphaeria maculans est un Dothideomycète phytopathogène capable d’alterner des modes de vie saprophyte, hemibiotrophe endophyte et nécrotrophe durant son cycle infectieux sur le colza. Afin de comprendre cette plasticité infectieuse, une mutagenèse aléatoire à grande échelle par ATMT a permis de générer une collection de 5000 transformants. L’objectif principal de cette thèse était d’exploiter cette collection en prenant avantage de la disponibilité d’outils de génomique, pour, d’une part, comprendre les mécanismes d’intégration de l’ADN-T dans le génome, et d’autre part, identifier des déterminants du pouvoir pathogène ciblés par l’ADN-T dans des mutants affectés dans leur capacité infectieuse. Une analyse systématique de 318 pieds d’insertion a été réalisée dans le but de d’évaluer les caractéristiques de l’insertion de l’ADN-T. Ce dernier est fréquemment inséré dans les régions actives riches en gènes, et favorise des gènes impliqués dans des processus biologiques indicatifs d’une conidie germante. Un biais marqué des insertions en faveur des régions régulatrices est observé ainsi qu’une corrélation entre la densité des insertions et le skew CG près du site d’initiation de la transcription. Ces observations sont cohérentes avec le modèle de ciblage intranucléaire de l’ADN-T. Enfin, l’existence de micro-homologies entre le site de pré-insertion et la bordure gauche de l’ADN-T indique une intégration par voie de recombinaison homologue (HR) et/ou microhomologue (MMEJ). Une approche multicritère a été utilisée pour caractériser cette collection. Un test d’inoculation a permis d’identifier 166 mutants altérés dans leur pouvoir pathogène. La validation génétique de la co-ségrégation entre le phénotype altéré et la présence de l’ADN-T indique que 44% des mutants montrant un déterminisme monogénique de l’altération sont effectivement étiquetés. Parmi les mutants altérés, 35 ont été analysé pour : (i) le phénotype de croissance en conditions usuelles de culture et en réponse aux stress oxydatif, UV et nutritif, (ii) le lien entre altération de la germination et pouvoir pathogène. Les gènes affectés par l’intégration de l’ADN-T, ont été identifié et analysé dans la souche sauvage à l’aide de données de transcriptomique. Ces cribles ont permis de décomposer le phénotype d’altération in planta en plusieurs phénotypes in vitro. Le plus fréquemment, les mutants ne sont pas altérés dans leur in vitro croissance, mais la plupart sont sensibles aux ROS. Les analyses d’expression au cours de l’infection indiquent que les gènes codant pour des effecteurs et ceux impliqués dans la détoxification des ROS, ont des dynamiques d’expression inverses et bi-phasiques, en lien avec le style de vie hemibiotrophe de L. maculans. Les 42 gènes ciblés par l’ADN-T dans ces mutants ont été identifiés et leur fonction putative disséquée par bioinformatique et transcriptomique. Au final, nous avons identifié six mutants d’intérêt pour une caractérisation fonctionnelle. Deux de ceux-ci deux ont atteint un niveau de caractérisation suffisant pour l’émission d’une hypothèse de travail. Dans le mutant µ1165, l’ADN-T cible un gène codant pour une protéine ribosomale S17 (LmRPS17), dont la régulation dépendrait de la voie de signalisation du complex TORC1. Nos résultats préliminaires suggèrent, d’une part, que TORC1 est une cible potentielle de LmRPS17 et, d’autre part, que la phase biotrophe de l’infection chez L. maculans est probablement régulée par TORC1 via l’enzyme de détoxication des ROS SOD2. Dans le mutant µ444, l’ADN-T cible un gène codant pour un élément rétroviral putatif LmHYP1, largement conservé parmi les ascomycètes. Nos résultats suggèrent que LmHYP1 interviendrait dans la régulation de gènes impliqués dans le pouvoir pathogène, via la production de petits ARN interférents issus hypothétiquement du clivage de son ARN messager par la machinerie de défense anti-rétrovirale. La validation de ces deux hypothèses est en cours au laboratoire
The Dothideomycete phytopathogen Leptosphaeria maculans is capable to alternate saprophytic, hemibiotrophic, endophytic and necrotrophic life styles during a single infectious cycle on its host plant, Brassica napus. However, little is known about the determinants of such plasticity. As part of a large-scale insertional mutagenesis project aiming at the discovery of pathogenicity factors a collection 5000 transformants has been generated by ATMT. The main objective of my PhD was to take advantage of “omics” to extract biological value from L. maculans mutants collection for a better understanding of T-DNA integration features and further identification of pathogenesis determinants in this fungus. A systematic analysis of 318 T-DNA tags was performed in a large collection of transformants in order to evaluate the features of T-DNA integration in its particular TE-rich compartmentalized genome. The T-DNA integration was mainly targeted to gene-rich, transcriptionally active regions, and favored biological processes that are consistent with the physiological status of a germinating conidia. In addition, T-DNA integration was strongly biased towards regulatory regions, and mainly promoters. Consistently with the T-DNA intranuclear targeting model, the density of T-DNA insertion correlated with CG skew near the transcription initiation site. The existence of microhomologies between promoter sequences and the T-DNA LB flanking sequence was also consistent with T-DNA integration to host DNA mediated by homologous recombination and/or the microhomology-mediated end joining pathways. Based on this data, a multi-criteria approach was used to draw the more possible information from this collection by identifying all 166 mutants reliably affected in pathogenicity, and expanding the genetic analysis. Considering single-gene segregation of the pathogenicity phenotype, our data indicate a 44% ratio of actual tagging. In parallel, for a subset of 35 isolates of the collection, we (i) described growth patterns in regular culture conditions or in response to oxidative, UV or starvation stresses, (ii) evaluated the link between altered germination and pathogenicity, (iii) identified and annotated the genes putatively affected by the T-DNA integration, and (iv) analyzed kinetics of expression of these genes in the WT isolate using available microarrays. Our results showed that pathogenicity alteration phenotype could be broken down into a pattern of phenotypes in vitro including growth, germination defect and susceptibilities to oxidative burst, starvation and UV stresses. Our results showed that most of these mutants were not altered in axenic growth but showed enhanced sensitivity to reactive oxygen species (ROS). Furthermore, our results showed that effectors and ROS scavengers have inverted dynamics during plant infection, consistently with the biphasic hemibiotrophic growth of L. maculans. Also, 42 genes targeted by the T-DNA in these mutants were recovered and dissected. This catalogue allowed us to identify a series of promising mutants for further functional studies. Based on this screening, six mutants were subjected to further analyses but only two reached sufficient advance for hypothesis building. In mutant µ1165, the T-DNA targeted a ribosomal protein S17 (LmRPS17), a downstream component of target of rapamycin complex 1 (TORC1) pathway. Our preliminary results suggested that TORC1 is a potential a target of LmRPS17. Also, biotrophic growth is probably tuned by TORC1 via Super oxide dismutase 2 (SOD2). In mutant µ444, the T-DNA targeted a retroviral-like element LmHyp1 widely conserved among ascomycetes. Our results suggest that LmHyp1 probably acts as a regulatory element during plant infection as its cleavage by the antiretroviral defences is hypothesized to generate siRNAs that silences distant genes. Work on these mutants is in progress
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Pandolfi, Valesca. "Análise transcricional do fitopatógeno Fusarium graminearum Schwabe na interação antagonista com a bactéria Pantoea agglomerans Gavini." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-04052007-085012/.

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Gramíneas cultivadas, como trigo, cevada e milho são produtos agrícolas de fundamental importância no Brasil. Entre os fatores causadores de perdas na produção de grãos dessas espécies estão os estresses causados por fitopatógenos como Fusarium graminearum Schwabe (teleomorfo Gibberella zeae Schw.), agente causador da fusariose e de difícil controle químico, biológico ou mesmo genético. Uma estratégia que tem se mostrado eficiente no controle de doenças é a utilização de microrganismos antagonistas a diferentes fitopatógenos, dentre os quais destaca-se a bactéria P. agglomerans. O presente trabalho teve como objetivo identificar genes diferencialmente expressos em interações fungo fitopatogênico-microrganismo antagonista, considerando como modelo o sistema F. graminearum-P. agglomerans. A construção de uma biblioteca de cDNA de F. graminearum cultivado in vitro proporcionou a geração de 1.983 seqüências válidas, resultando em 1.283 unigenes. As categorias de maior representatividade desta biblioteca foram aquelas constituídas por proteínas envolvidas em vias da informação genética - DNA-RNA-proteína (26 %); proteínas hipotéticas (24 %) e proteínas do metabolismo (16 %). Tanto a categoria de proteínas envolvidas nos processos de desenvolvimento como as envolvidas na percepção a estímulos externos constituíram 10 % dos unigenes. Dentre os genes presumivelmente anotados, foram identificados aqueles codificadores de enzimas de importantes rotas metabólicas como gliceraldeído-3-fosfato-desidrogenase, fosfoglicerato quinases e fosfoenolpiruvato carboxilases, como também componentes produzidos pelo metabolismo secundário como micotoxinas e outras proteínas associadas a estresse e patogenicidade de fungos. Neste trabalho também foi verificado o potencial de antagonismo in vitro da bactéria P. agglomerans frente a três fitopatógenos de trigo: Drechslera tritici-repentis (Died.) Shoem e Bipolaris sorokiniana (Sacc. in Sorok.) e F. graminearum. Foi verificado que a inibição do crescimento destes fungos está associada à liberação de compostos solúveis e voláteis pela bactéria, que foram responsáveis por cerca de 50 % e 40 % de inibição, respectivamente. O perfil da expressão gênica de F. graminearum na interação com a bactéria P. agglomerans foi avaliado via macroarranjo. Dos 1.014 genes avaliados, 29 genes de F. graminearum foram diferencialmente expressos (p < 0,05) durante a interação com a bactéria antagonista, sendo 19 genes induzidos e 10 genes reprimidos. Entre os transcritos induzidos foram identificadas proteínas envolvidas nos processos de defesa e/ou virulência de fungos, cuja expressão foi induzida em resposta a estresses tanto abióticos como bióticos. Dos genes que foram reprimidos, destacaram-se: um transcrito com similaridade a uma proteína com um domínio do tipo dedo de zinco ?zinc finger? que é um fator de transcrição importante no processo de divisão celular, bem como proteínas envolvidas na cadeia respiratória, na modulação protéica e sinalização celular. Os dados do macroarranjo foram validados via transcrição reversa seguida de PCR quantitativo em tempo real (RT-PCRq), metodologia que se mostrou adequada para complementar a análise transcricional obtida por macroarranjo. As informações geradas na análise de antagonismo in vitro, bem como a análise e seqüenciamento dos transcritos, juntamente com a quantificação do nível de expressão na interação, foram fundamentais para compreender o padrão de resposta do fungo F. graminearum na interação com a bactéria P. agglomerans.
Cultivated grasses such as wheat, barley and maize are agricultural products of fundamental economic and social importance in Brazil. Among causing factors of important grain production losses in these species are diseases caused by phytopathogenic fungi such as Fusarium graminearum Schwabe (teleomorfo Gibberella zeae Schw.), the causal agent of fusariosis, a disease of difficult chemical, biological or even genetic control. An efficient and promising strategy to be adopted in order to protect cultivated plants against such diseases is the selection of antagonist microorganisms, amongst them the bacteria Pantoea agglomerans. This microbiota might have an important impact in scab control, isolated or in an integrated management program with chemical treatment. The present work aimed at identifying differentially expressed sequences in pathogenic fungi-antagonistic microorganisms interactions, considering the F. graminearum ? P. agglomerans model. The construction of a cDNA library for F. graminearum grown in PDA medium generated 1,983 valid sequences and provided 1,283 unigenes. The most representative categories in this library were proteins involved in genetic information pathways, DNA-RNA-protein (26 %); hypothetical proteins (24 %); and proteins involved in metabolism (16 %). The protein category involved in developmental processes as well as those related to external stimuli perception comprised 10 % of the obtained unigenes. Among putatively annotated genes, some coding for enzymes of important metabolic routes were identified, such as glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase and phophoenolpyruvate carboxylase. Also secondary metabolism compounds, specially micotoxins and proteins related to fungi stresses and pathogenicity were identified. In the present work, the control of three wheat phytopathogens, Drechslera tritici-repentis (Died.) Shoem, Bipolaris sorokiniana (Sacc.in Sorok.) and F. graminearum, using specific isolates of P. agglomerans was demonstrated. It was observed that the 50 % and 40 % growth inhibition of these fungi is associated to the bacteria release of soluble and volatile compounds, respectively. The gene expression profile of F. graminearum during interaction with the bacteria P. agglomerans was evaluated via macroarray. Among the 1,014 analysed genes, 29 F. graminearum genes were differentially expressed (p < 0,05) during its interaction with the antagonist bacteria: 19 genes were induced while 10 genes were repressed. Among the induced transcripts, proteins involved in fungi defense and/or virulence processes were identified, whose expression was induced in reponse to abiotic or biotic stresses. Among the identified repressed genes, a transcript similar to a protein containing a zinc finger-type domain, a transcription factor relevant in cell division, deserves special attention, as well as proteins involved in respiratory chain, in protein modulation and in cell signaling. Additionally, the macroarray data were validated by reverse transcription followed by real-time quantitative PCR (RT-PCRq), a suitable method for complementing transcriptional analysis through macroarray. Finally, the information generated in in vitro pathogenic fungi-antagonistic microorganisms interactions analysis, as well as in the analysis and sequencing of the obtained transcripts, together with the determination of the level of expression during the evaluated interactions were essential for better understanding the response pattern of the fungus F. graminearum in interaction with the bacteria P. agglomerans
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28

Freeman, Brian C. "The role of water stress in plant disease resistance and the impact of water stress on the global transcriptome and survival mechanisms of the phytopathogen Pseudomonas syringae." [Ames, Iowa : Iowa State University], 2009.

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29

Singla, Meenu. "Occurrence and Relevance of Trans-kingdom RNAi against Phytopathogenic Bacteria." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS375.pdf.

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Nous avons généré et caractérisé des lignées transgéniques d'Arabidopsis exprimant des petits ARN artificiels dirigés contre des gènes de virulence de Pto DC3000. Nous avons constaté que ces petits ARN exprimés par les plantes d’Arabidopsis étaient capables de réprimer l'expression des gènes bactériens cibles au cours de l'infection. Ce phénomène d’extinction de gène antibactérienne (AGS) était associé à une diminution de la pathogénèse bactérienne, également observée lors de l'application externe de petits ARN dérivés des plantes correspondantes sur des feuilles sauvages d'Arabidopsis et de tomate. De plus, nous avons découvert que ces espèces de petits ARN de plantes étaient responsables à la fois de l'AGS et de la suppression de la pathogenèse. Cela implique que la bactérie Gram-négative Pto DC3000 est capable d’internaliser, de manière passive et/ou active, des petits ARN malgré la présence d'une paroi cellulaire comprenant une structure complexe à double membrane, à savoir les membranes interne et externe de la bactérie. De plus, nous avons découvert que les petits ARN apoplastiques fonctionnels étaient soit intégrés dans des vésicules extracellulaires (EV), soit présent dans l’espace extracellulaire sous une forme libre. Ce travail de thèse révèle donc un tout un nouveau phénomène de régulation trans-règne entre un hôte eucaryote et un agent pathogène procaryote et a permis de faire avancer de manière significative nos connaissances dans les domaines de la biologie de l’ARN, de la microbiologie et des interactions hôte-bactérie
We first generated and characterized Arabidopsis-based transgenic systems expressing artificial small RNAs directed against key virulence-associated genes from Pto DC3000. Interestingly, we found that these Arabidopsis-encoded small RNAs were competent in repressing the expression of the targeted virulence factors during infection. This Antibacterial Gene Silencing (AGS) phenomenon was associated with a reduced bacterial pathogenesis, which was also observed upon external application of corresponding plant-derived small RNAs onto wild-type Arabidopsis and tomato leaves prior to infection. Furthermore, we demonstrated that these plant small RNA species were causal for both AGS and pathogenesis suppression. This implies that the Gram-negative bacterium Pto DC3000 is capable of taking-up –passively and/or actively– small RNAs despite the presence of a cell wall comprising an intricate double membrane structure, namely the bacterial inner and outer membranes. In addition, we discovered that apoplastic small RNAs, which are competent for AGS, were either embedded into Extracellular Vesicles (EVs) or presumably in a free form. The latter small RNA species have not yet been reported and were referred to as Extracellular Free Small RNAs (efsRNAs). Overall, this thesis work unveils a novel phenomenon of trans-kingdom regulation between a eukaryotic host and a prokaryotic pathogen
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30

Conti, Raphael. "Micro-organismos de interesse farmacêutico e agrícola: estudo químico e biossintético." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/60/60138/tde-04092012-162732/.

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A biodiversidade microbiana de diferentes ecossistemas tem incentivado estudos químicos e biológicos com micro-organismos dos mais variados habitats, os quais têm conduzido à obtenção de moléculas bioativas com aplicações na medicina, indústria química e agricultura, proporcionando melhorias na qualidade de vida ao homem. O presente trabalho teve como objetivos a bioprospecção por actinobactérias endofíticas e seus metabólitos, além do estudo da via biossintética dos sesquiterpenos aristoloquenos produzidos pelo fungo fitopatogênico Botrytis cinerea. No estudo de bioprospecção foram isoladas 41 linhagens de actinobactérias endofíticas de duas espécies de Asteraceae (Thitonia diversifolia e Lychnophora ericoides). A identificação através do sequenciamento de DNAr indicou predominância do gênero Streptomyces. As linhagens foram cultivadas em meio de arroz e os extratos etanólicos submetidos aos ensaios de citotoxicidade frente a células tumorais e antimicrobiano. Um total de 58,5% dos extratos apresentou atividade em pelo menos um dos ensaios realizados. Foram selecionadas as linhagens Streptomyces cattleya RLe 4 e Streptomyces sp. RLe 8 para cultivo em escala ampliada, isolamento e identificação de metabólitos bioativos. O isolamento dos compostos foi realizado através de diferentes técnicas cromatográficas e a identificação estrutural foi baseada em dados de ressonância magnética nuclear de 1H e 13C e espectrometria de massas. De S. cattleya RLe 4 foram isolados quatro compostos: 2-hidroxibenzamida, desferrioxamina E, 1-(3\',4\'-dimetoxifenil)-1-propanona e 1-(3\',4\'-dimetoxifenil)-1-etanona. Dos extratos de Streptomyces sp. RLe 8 foram isolados dez compostos: benzamida, 3- hidroxibenzamida, 3-hidróxi-4-metoxibenzamida, 4-hidróxi-3-metoxibenzamida, 3,4- dimetoxibenzamida, 2-fenilacetamida, dois isômeros de 3,4-diidro-3,4,6,8-tetraidróxi-1(2H)- naftalenona, 2,3-diidro-2,2-dimetil-4(1H)-quinazolinona e desferrioxamina B. O composto 2,3-diidro-2,2-dimetil-4(1H)-quinazolinona apresentou elevada atividade frente as células de câncer de cólon (HCT-8) e glioblastoma (SF295), com 93,9 % e 87.0 % de inibição, respectivamente. O outro enfoque da tese envolveu a otimização da produção de sesquiterpenos aristoloquenos por linhagens de B. cinerea, seguido de estudo biossintético destes produtos naturais através de experimentos de incorporação de precursores isotopicamente enriquecidos com 2H (deutério) e 13C (carbono treze). As análises dos dados obtidos de RMN de 2H e de 13C do sesquiterpeno majoritário indicaram que a biossíntese desta substância ocorre pela via do mevalonato (MVA). Os resultados também sugeriram o possível envolvimento da via do metil-eritritolfosfato ou 1-desoxi-D-xilulose-fosfato (MEP/DPX) na biossíntese deste sequiterpeno. Estes resultados podem contribuir para o planejamento racional de fungicidas seletivos com aplicação na agricultura. O trabalho desenvolvido mostrou o grande potencial de actinobactérias endofíticas para a obtenção de moléculas bioativas e que estudos usando precursores isotopicamente marcados fornecem informações precisas acerca da origem biossintética de produtos naturais.
The microbial biodiversity from different ecosystems has incited chemical and biological studies with microorganisms from several habitats, leading to the isolation of bioactive natural products with applications in medicine, chemical industry and agriculture, and thus contributing to a better quality of life. This thesis aimed the biopropecting on endophytic actinobacteria and their natural products, and also the biosynthetic study of aristolochene sesquiterpenes in the phytopathogenic fungus Botrytis cinerea. A total of 41 actinobacterial strains were isolated of two Asteraceae species (Thitonia diversifolia and Lychnophora ericoides) for the bioprospecting study. The rDNA sequencing showed predominancy of Streptomyces genus. All the strains were cultured on rice medium, and the ethanolic extracts were screened in cytotoxity and antimicrobial assays. As a result, 58.5% of the extracts showed activity in al least one bioassay. The strains Streptomyces cattleya RLe 4 and Streptomyces sp. RLe 8 were selected for scale up cultures, isolation and identification of bioactive compounds. Different chromatographic methods were applied for the isolation of compounds, and structural analysis were based on 1H and 13C nuclear magnetic resonance and mass spectrometry data. Four compounds were isolated from S. cattleya RLe 4: 2- hydroxybenzamide, desferrioxamine E, 1-(3\',4\'-dimethoxyphenyl)-1-propanone, and 1-(3\',4\'- dimethoxyphenyl)-1-etanone. Ten compounds were isolated from Streptomyces sp. Rle 8: benzamide, 3-hydroxybenzamide, 3-hydroxy-4-methoxybenzamide, 4-hydroxy-3- methoxybenzamide, 2-phenylacetamide, two isomers of 3,4-dihydro-3,4,6,8-tetrahydroxy- 1(2H)-naphthalenone, 2,3-dihydro-2,2-dimethyl-4(1H)-quinazolinone, and desferrioxamine B. Compound 2,3-dihydro-2,2-dimethyl-4(1H)-quinazolinone showed high antiproliferative activity against colon cancer cells (HCT-8) and glioblastoma cells (SF295), with 93.9 and 87.0% of inhibition, respectively. The second focus of the thesis involved the optimization of aristolochene sesquiterpenes production by two strains of B. cinerea, followed by the biosynthetic study through feeding experiments with 2H (deuterium) and 13C isotopically labeled precursors. The 2H and 13C NMR obtained data showed that the biosynthesis of the sesquiterpene proceeds by the mevalonate pathway (MVA). The results also suggested the possible participation of the non mevalonate pathway, methylerytritol phosphate ou 1-deoxy- D-xylulose phosphate (MEP/DXP), in the biosynthesis. These results might contribute to the rational design of selective fungides with application in agriculture. This thesis showed the endophytic actinobacteria as promising sources of bioactive natural products, and also showed that the isotopically labeled feeding experiments give reliable information about the natural products biosynthetic pathways.
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31

Olsson, Johan. "Modern methods in cereal grain mycology /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5792-0.pdf.

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32

Puric, Jelena [UNESP]. "Fungos de sedimentos marinhos da Antártica: produção de metabólitos secundários e avaliação da atividade contra espécies de Xanthomonas." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153548.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho teve como objetivo obter extratos contendo metabólitos secundários de fungos filamentosos isolados de sedimentos marinhos da Antártica e avaliar sua potencial atividade antibacteriana em Xanthomonas citri subsp. citri, Xanthomonas euvesicatoria e Xanthomonas axonopodis pv. passiflorae (bactérias fitopatogênicas que causam doenças em cítricos, pimenta e tomate, e maracujá, respectivamente). Entre os 90 extratos brutos intracelulares e extracelulares obtidos a partir de fungos, 19 mostraram a capacidade de impedir o crescimento de X. citri subsp. citri e X. euvesicatoria in vitro e 22 mostraram a capacidade de dificultar o crescimento de X. axonopodis pv. passiflorae in vitro. Os extratos extracelulares inibiram em média 97,12% de X. citri subsp. citri, 95,94% de X. euvesicatoria e 96,58% de X. axonopodis pv. passiflorae a 3,0 mg / mL.
This work aimed to obtain extracts containing secondary metabolites from filamentous fungi isolated from marine sediments from Antarctic and assess their potential antibacterial activity on Xanthomonas citri subsp. citri, Xanthomonas euvesicatoria and Xanthomonas axonopodis pv. passiflorae (phytopathogenic bacteria causing diseases in citrus, pepper and tomato, and passionfruit, respectively). Among the 90 raw intracellular and extracellular extracts obtained from fungi, 19 showed the ability to hamper the growth of Xanthomonas citri subsp. citri and X. euvesicatoria in vitro and 22 showed the ability to hamper the growth of X. axonopodis pv. passiflorae in vitro. The extracellular extracts inhibited on average 97,12% of Xanthomonas citri subsp, 95,94% of X. euvesicatoria and 96,58% of X. axonopodis pv. passiflorae at 3,0 mg/mL.
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33

Barthélémy, Morgane. "Etude de la diversité chimique et biologique d’endophytes de palmiers." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS563.

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Dans cette étude, le palmier Astrocaryum sciophilum a été choisi comme modèle pour l'étude de ses endophytes foliaires. Du fait de sa longévité, nous avons cherché à mettre en évidence une communauté compétitive d’endophytes en fonction de l’âge de ses feuilles. Afin d’évaluer si les métabolites produits par ces endophytes pourraient être utilisés en santé humaine, les extraits de chaque endophyte ont été testés contre Staphylococcus aureus résistant à la méticilline (SARM) ainsi que pour leur activité quorum quenching (QQ). En parallèle, afin d’identifier un rôle écologique de protection de la plante par ces endophytes, des co-cultures ont été réalisées avec le phytopathogène Fusarium oxysporum. Plusieurs extraits de souches ont été sélectionnés afin d’isoler et d’identifier le ou les métabolites responsables des activités biologiques observées. Différents outils analytiques ont permis de guider le processus d’isolement (LC-MS/MS, réseaux moléculaires et imagerie par spectrométrie de masse). L’étude de la communauté d’endophytes isolée des feuilles âgées n’a pas mis en évidence un arsenal chimique plus compétitif. Toutefois, deux souches bactériennes du genre Luteibacter sp. ont montré un extrait actif sur SARM et de nombreux extraits de bactéries présentent une activité QQ. Par la suite, le métabolome secondaire du genre Colletotrichum a été étudié à l’aide des réseaux moléculaires et un champignon de la famille des Xylariaceae a été étudié pour son activité contre F. oxysporum. Dans le cadre de cette thèse, sept souches endophytes ont été étudiées chimiquement permettant l’isolement et l’identification de 42 molécules dont dix sont nouvelles
The palm Astrocaryum sciophilum is the host plant model chosen in this work. Indeed, due to the longevity of its leaves, we expected to highlight a competitive community of endophytes within the oldest leaves. Thus, 197 endophytes have been isolated and identified from different leaves of six palm specimens. In order to evaluate whether the compounds produced by these microorganisms could be used for the treatment of human disease, the ethyl acetate extracts of each endophyte were tested against methicillin-resistant Staphylococcus aureus (MRSA) as well as for a quorum quenching (QQ) activity. Simultaneously, co-culture were carried with the fungi Fusarium oxysporum in order to highlight endophytes providing plant protection against phytopathogens. We selected extracts in order to isolate and identify the bioactive metabolites. Various analytical tools have been used to improve the isolation process (LC-MS/MS, molecular networking or MS imaging).The study of the endophytic community isolated from older leaves did not show a more competitive chemical arsenal. However, two Luteibacter strains exhibited an ethyl acetate extract active against MRSA and several bacteria provide quorum quenching extracts. The metabolome of Colletotrichum genus was studied using molecular networking and a fungus from the Xylariaceae family was studied for its capacity to inhibit F. oxysporum’s growth. In our study, seven endophyte strains were chemically investigated leading to the isolation and identification of 42 molecules whose ten are new
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34

Rocha, Flávio. "Bioprospecção de plantas da família Solanaceae com atividade fungitóxica à Moniliophthora perniciosa." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-17112015-085928/.

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O fungo Moniliophthora perniciosa, fitopatógeno responsável pela doença vassoura-de-bruxa no cacaueiro, é responsável por reduzir a produtividade de frutos de cacau nas Américas. Visto que os métodos atuais de controle desta doença não são eficientes, faz-se necessário a busca por compostos para seu controle químico. Os produtos naturais têm contribuído na síntese de novos pesticidas e a família Solanaceae é reconhecida como uma fonte promissora de compostos antifúngicos. Neste contexto, este trabalho teve por objetivo explorar o potencial biológico e químico de metabólitos secundários produzidos por plantas da família Solanaceae com atividade antifúngica à M. perniciosa. Para tanto, extratos aquosos de folhas de dez plantas foram avaliados quanto sua atividade inibitória a M. perniciosa e, observou-se maior atividade antifúngica pelos extratos de Cestrum nocturnum, Solanum seaforthianum e Brunfelsia uniflora. Destas, as plantas S. seaforthianum e B. uniflora mostram-se como promissoras e foram selecionadas para isolamento de seus compostos ativos. A partir do extrato aquoso de S. seaforthianum obteve-se duas frações constituídas por saponinas furostanas, a mistura (25R)-karatavioside C / (25R)-purpureagitoside, com CI50 de 40,9 μg mL-1, e a mistura (25R)-timosaponin H1/ (25R)-uttroside B, com CI50 de 22,3 μg mL-1 ao crescimento micelial. E, a partir do extrato aquoso de B. uniflora obteve-se três compostos da classe das saponinas espirostanas, o composto karatavioside A e os compostos parcialmente identificados BuM8i4, com aglicona identificada como (25R)-yucagenina, e BuM8i6, com aglicona identificada como (25R)-diosgenina, todos com CI50.< 15,63 μg mL-1 ao crescimento micelial de M. perniciosa. Todos os compostos caracterizados neste trabalho estão sendo relatados pela primeira vez a partir das plantas estudas e também para atividade antifúngica.
The fungal phytopathogen Moniliophthora perniciosa is the causal agent of Witches\' Broom disease and the main responsible by limiting cacao production in Americas. The current disease control methods are not efficient and new antifungal compounds are necessary to the chemical management. Natural products has contributed to the development of natural product-based pesticides and the Solanaceae plants are known as a promising source of antifungal compounds. In this context, this work aimed to explore the biological and chemical potential of secondary metabolites produced by Solanaceae plants with antifungal activity against M. perniciosa. For this, antifungal activity of water extracts from leaves of ten plants was evaluated against M. perniciosa and the best results were observed by using extracts from Cestrum nocturnum, Solanum seaforthianum e Brunfelsia uniflora. Among these plants, S. seaforthianum and B. uniflora were selected for active compounds isolation due to their promising characteristics. From water extract of S. seaforthianum two furostan saponin fractions were obtained, the mixture (25R)-karatavioside C / (25R)- purpureagitoside, with IC50 of 40,9 μg mL-1, and the mixture (25R)-timosaponin H1/ (25R)-uttroside B, with IC50 of 22,3 μg mL-1 to the mycelial growth. From water extract of B. uniflora three spirostan saponin compounds were obtained, the compound karatavioside A and the compounds partially identified BuM8i4, with aglycone identified as (25R)-yucagenina, and BuM8i6, with aglycone identified as (25R)- diosgenina, all these compounds showed IC50< 15,63 μg mL-1 to the mycelial growth of M. perniciosa. All compounds characterized in this study were obtained for the first time from these plants and also described about their antifungal activity.
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35

Silva, Patrícia Isabela Pessoa da. "Identificação de genes com expressão modulada por estreptomicina e de genes associados à virulência e patogenicidade em Xylella fastidiosa." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-01032011-140806/.

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Em concentrações subletais, agentes antimicrobianos modulam a expressão gênica bacteriana, sendo que o conjunto de genes que é modulado depende tanto da cepa bacteriana, como da natureza do agente antimicrobiano. Neste trabalho, avaliamos o perfil de expressão gênica de Xylella fastidiosa cepa 9a5c em resposta ao tratamento por até 60 minutos com dose subletal do antibiótico estreptomicina. Esta é uma cepa virulenta, originalmente isolada de laranjeiras com sintomas de clorose variegada dos citros. A hibridização de microarranjos de DNA representando 2608 das 2848 sequências codificadoras (CDS) previamente anotadas no genoma desta cepa, revelou que 136 CDS apresentaram expressão gênica diferencial em resposta à exposição à estreptomicina, sendo que destas 109 foram negativamente moduladas e 27 positivamente moduladas. Realizamos, também, ensaios de PCR quantitativo precedido de transcrição reversa (RTqPCR) de 21 CDS para confirmar a modulação observada na análise global da expressão gênica. O perfil de expressão gênica de X. fastidiosa em resposta à estreptomicina foi analisado de forma integrada com outros perfis de expressão gênica desta bactéria. Entre as CDS positivamente moduladas, destacamos aquelas codificadoras das chaperoninas GroEL e GroES, que estão associadas a resposta de choque térmico, e CDS associadas à tradução, tais como proteínas ribossomais e fatores de tradução. Interessantemente, a exposição à estreptomicina induz a expressão da CDS que codifica poligalacturonase, que é um fator de virulência em algumas cepas de X. fastidiosa. Por outro lado, o tratamento com estreptomicina promoveu a modulação negativa de CDS relacionadas à formação e manutenção de biofilme ao contrário do observado quando estas bactérias foram submetidas ao tratamento com gomesina, um peptídeo antimicrobiano. O conjunto destas observações sugere que a exposição à dose subletal de estreptomicina possa promover um fenótipo de maior virulência, contrariamente ao efeito previamente observado com a gomesina. Neste trabalho, também descrevemos o pirosequenciamento do genoma da cepa J1a12 de Xylella fastidiosa, que exibe fenótipo menos virulento em citros e tabaco em relação à cepa 9a5c. A comparação da sequência genômica destas duas cepas confirma diferenças anteriormente observadas utilizando-se microarranjos de DNA e destaca genes potencialmente importantes para virulência de Xylella fastidiosa.
At sublethal concentrations, antimicrobials compounds modulate bacterial gene expression and the gene set that is modulated depends not only on the bacterial strain but also on the nature of antimicrobial agent. In this study, we evaluated changes in gene expression profile of Xylella fastidiosa strain 9a5c exposed up to 60 min to sublethal concentration of streptomycin. This a virulent strain originally isolated from orange trees with symptoms of citrus variegated chlorosis. Hybridization of DNA microarrays representing 2,608 out of 2848 coding sequences (CDS) previously annotated in strain 9a5c genome revealed 136 CDS differentially expressed upon streptomycin treatment. Of which 109 were down-regulated and 27 up-regulated. Differential expression for a subset of 21 CDS was further evaluated by reverse transcriptionquantitative PCR (RT-qPCR). In addition, we performed an integrated analysis of the gene expression profile of X. fastidiosa in response to streptomycin along with other gene expression profiles available for this bacterium. Among the up-regulated CDS, we highlight those encoding chaperonins GroEL and GroES, which are associated with heat shock response, and those CDS related to translation, such as ribosomal proteins and translation factors. Interestingly, exposure to streptomycin induces the expression of a CDS encoding polygalacturonase, which is a virulence factor for some X. fastidiosa strains. Furthermore, treatment with streptomycin down-regulates some CDS related to biofilm formation oppositely to treatment with gomesin, an antimicrobial peptide. Together, these observations suggest that exposure to sublethal dose of streptomycin might promote a higher virulent phenotype, in contrast to the effect previously observed with gomesin. In the present work, we also describe the pyrosequencing of J1a12 genome, a X. fastidiosa strain that exhibits a less virulent phenotype in citrus and tobacco if compared to strain 9a5c. A comparison of genome sequences of these two strains confirms differences previously observed using DNA microarrays and highlights important genes for virulence of X. fastidiosa.
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36

Pierry, Paulo Marques. "Pirossequenciamento e análise comparativa de genomas do fitopatógeno Xylella fastidiosa." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-15052012-104940/.

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Xylella fastidiosa é uma bactéria Gram-negativa, do subgrupo das Gama-Proteobactérias, não-flagelada, que coloniza o xilema de diversas plantas cultivadas e silvestres, podendo ser causadora de doenças. Sua disseminação é feita por insetos conhecidos como cigarrinhas. Genomas de cepas de X. fastidiosa isoladas de distintos hospedeiros já foram sequenciados completa ou parcialmente: 9a5c de citros; Temecula-1 e GB514 de videira; Dixon, M12 e M23 de amendoeira; Ann-1 de espirradeira e EB92-1, isolada de sabugueiro e utilizada como bio-controle para Doença de Pierce de videiras. Estudos de genômica comparativa associados a abordagens de genômica funcional e de genética molecular têm possibilitado o estudo detalhado de mecanismos potencialmente relevantes tanto para a colonização de plantas e insetos por este fitopatógeno como para o desenvolvimento de sintomas associados a doenças específicas em seus respectivos hospedeiros vegetais. Exceto o genoma de 9a5c, todos os demais genomas conhecidos são de cepas isoladas na América do Norte. Neste trabalho descrevemos o pirossequenciamento dos genomas da cepa J1a12, que exibe fenótipo não-virulento em citros, e das cepas Pr8x e Hib4, isoladas, respectivamente, de ameixeira e hibisco. A cepa J1a12 possui além de seu cromossomo principal de 2.788.789 pb dois plasmídeos, pXF51 e pXF27, respectivamente de 51.180 pb e 27.268 pb. pXF51 já foi descrito também na cepa de citros 9a5c e pXF27 tem similaridade com outros plasmídeos de cepas de X. fastidiosa norte-americanas isoladas de amoreira e videira. A cepa Pr8x possui além de seu cromossomo principal de 2.666.242 pb um plasmídeo, pXF39, de 39.580 pb, o qual contém a maioria das CDS presentes no pXF51. A cepa Hib4, isolada de hibisco, tem o maior cromossomo (2.813.297 pb) e também o maior plasmídeo (pXF64 com 64.251 pb) já descritos para X. fastidiosa. pXF64 apresenta extensa similaridade com o plasmídeo pBVIE04 de Burkholderia vietnamensis cepa G4, sendo descrito pela primeira vez em cepas de X. fastidiosa. Análises comparativas destes genomas possibilitaram a identificação de alterações que podem ser correlacionadas com os fenótipos exibidos por estas cepas, além da variedade e diversidade de regiões relacionadas a bacteriófagos e de plasmídeos que co-existem nas diferentes cepas deste fitopatógeno.
Xylella fastidiosa is a Gram-negative bacteria, of the Gamma-proteobacterium subgroup, non-flagellated that colonizes the xylem of several cultivated and wild plants, where may cause disease. The bacterium is spread by insects known as sharpshooters. Genomes of X. fastidiosa strains isolated from different hosts have been completely or partially sequenced: 9a5c from citrus; Temecula-1 and GB514 from grapevine; Dixon, M12 and M23 from almond tree; Ann-1 from oleander and EB92-1, isolated from elderberry and used as bio-control for Pierce\'s disease of grapevines. Comparative genomics studies associated with approaches from functional genomics and molecular genetics have allowed a detailed study of mechanisms potentially relevant to the colonization of plants and insects by this pathogen as well as to the development of symptoms associated with specific diseases in their respective host plants. Except for 9a5c, all other known genomes are from strains isolated in North America. Here we describe the pyrosequencing of the genomes of strain J1a12, which displays non-virulent phenotype in citrus and of Pr8x and Hib4 strains isolated, respectively, from plum and hibiscus. J1a12 has a main chromosome of 2,788,789 bp and two plasmids, pXF51 and pXF27, respectively of 51,180 bp and 27,268 bp. pXF51 has been described also in the citrus strain 9a5c and pXF27 has similarity with other plasmids found in North American strains isolated from mulberry tree and grapevine. The strain Pr8x has a main chromosome of 2,666,242 bp and one plasmid, pXF39, of 39,580 bp which present similarities with pXF51. Hib4, the strain isolated from hibiscus, has the largest chromosome (2,813,297 bp) and the largest plasmid (pXF64 with 64,251 bp) described for X. fastidiosa. pXF64 shows extensive similarity with the plasmid pBVIE04 of Burkholderia vietnamensis G4 strain and is described for the first time in X. fastidiosa. Comparative analyzes of these genomes have identified several differences that may be correlated with the phenotypes displayed by these strains, in addition to the variety and diversity of regions related to bacteriophages and plasmids that co-exist in different strains of this pathogen.
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37

Junior, Gildemberg Amorim Leal. "Avaliação da expressão de genes de T. cacao e C. perniciosa associados a resistência e patogenicidade no período assintomático da doença Vassoura-de-Bruxa." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-04042007-141647/.

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O basidiomiceto Crinipellis perniciosa (Stahel) Singer (Tricholomataceae), é um parasita hemibiotrófico causador da doença Vassoura-de-Bruxa do cacaueiro (Theobroma cacao) . Os sintomas da vassoura incluem o excesso de brotações em ramos e almofadas florais, abortamento de flores e frutos novos e formação de manchas necróticas nos frutos em maturação. Causando perda na produção. Para a identificação de genes diferencialmente expressos no hospedeiro, no período assintomático, duas bibliotecas subtrativas foram construídas confrontando o genótipo suscetível ‘ICS 39’ e o resistente ‘CAB 214’, inoculados. Uma análise detalhada de 23 genes por PCR quantitativo revelou diferenças na cinética da indução no período assintomático. A indução dos genes no genótipo suscetível em resposta ao C. perniciosa foi atrasada e reduzida, e no resistente houve uma indução mais rápida e intensa, com dois momentos de indução (24 e 120 horas após inoculação). Os genes e mecanismos de patogenicidade Crinipellis perniciosa são amplamente desconhecidos. Genes presumíveis de patogenicidade de Crinipellis perniciosa foram identificados em uma biblioteca enriquecida por hibridização subtrativa supressiva para genes induzidos sob baixa disponibilidade de Nitrogênio. Oito genes foram avaliados para expressão in vitro e em plantas inoculadas por amplificação quantitativa de transcritos reversos (RT-qPCR) e, dos sete expressos diferencialmente sob a carência de N, seis foram induzidos durante os períodos assintomáticos, corroborando a hipótese de convergência na via de sinalização para estresse nutricional abiótico e a patogênese.
The basidiomycete Crinipellis perniciosa (Stahel) Singer (Tricholomataceae) is the causal agent of witches' broom disease in Theobroma cacao (cacao). The hemibiotrophic pathogen infects meristematic tissues (shoots, flower cushions, single flowers and developing fruits). Hypertrophic growth of infected buds (?brooms?) is the most dramatic symptoms, but economic losses result from pod infection. To identify genes differentially expressed in the host during the symptomless stage, two subtractive suppressive libraries were constructed, subtracting in both directions transcripts from the inoculated susceptible genotype ‘ICS 39’ and from the resistant ‘CAB 214’. Quantitative reverse transcription amplification (RT-qPCR) of 23 genes identified as differentially expressed revealed distinct kinetics of gene induction at the asymptomatic stage. Expression induction in the susceptible genotype in response to C. perniciosa was delayed and limited, while in the resistant, there was a quicker and more intense reaction, with two peaks of gene induction at 48 and 120 h after inoculation.. Pathogenicity genes and mechanisms of Crinipellis perniciosa are laregly unknown.. Putative pathogenicity genes from Crinipellis perniciosa were identified in a cDNA library enriched by subtractive suppressive hybridization for genes induced under limiting Nitrogen. The eight genes were analysed for expression by quantitative amplification of reversed transcripts (RT-qPCR) in vitro and inoculated plants, and from the seven differentially expressed under N deprivation, six were induced under the symptomless stage of the disease, corroborating the hypothesis of convergence between the signal pathway for nutritional stress and pathogeneis.
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38

Peters, Leila Priscila. "A more detailed view of reactive oxygen species metabolism in the sugarcane and Sporisorium scitamineum interaction." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-23012017-094942/.

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Sugarcane (Saccharum spp) is an important commercial crop cultivated widely in tropical and subtropical countries. Primarily sugarcane is used to produce sugar and recently it is proven to be a valuable resource for bioethanol, biodiesel, bioplastic and bioelectricity. Smut is one of the most serious sugarcane disease and occurs in sugarcane fields all over the world. The disease is caused by the biotrophic fungus Sporisorium scitamineum. The fungus induces metabolic changes in the plant leading to the production of a whip-like structure where fungal sporogenesis take place. The objective of this study was to analyse the reactive oxygen species (ROS) production, antioxidant enzymes activity and expression of genes associated with the ROS metabolism in smut susceptible (IAC66-6) and resistant sugarcane genotypes (SP80-3280). In addition, this work assessed the relationship between antioxidant enzymes and sensitivity of S. scitamineum to exogenous hydrogen peroxide (H2O2). This thesis is presented in the format of two chapters (chapters 2 and 3). In the second chapter, the results revealed that there were variations in the antioxidant system as well as in the ROS production in resistant sugarcane genotype, whereas few changes occurred in the susceptible genotype inoculated with S. scitamineum. Microscopic analysis revealed that S. scitamineum teliospore germination and appressorium formation were delayed during early infection in the smut resistant genotype, which coincided with H2O2 accumulation. In chapter 3, the results demonstrated that S. scitamineum is highly resistant to exogenous H2O2. At 2 mM exogenous H2O2 concentration the fungus presented an effective antioxidant system in response to the secondary products of oxidative stress. Furthermore, S. scitamineum when exposed for a long time at 2 mM exogenous H2O2 concentration it can acquire an adaptive response to H2O2. The results obtained in this study contributed to increase the understanding of this very complex interaction between sugarcane and S. scitamineum and it will be helpful toward understanding which aspects are involved in the resistance to S. scitamineum. These informations are important to create strategies for improving smut resistance in sugarcane.
Cana-de-açúcar (Saccharum spp) é uma importante cultura comercial amplamente cultivada em países tropicais e subtropicais. A cana-de-açúcar é principalmente utilizada para produzir açúcar e recentemente é considerada uma valiosa fonte para produção de bioetanol, biodiesel, bioplásticos e bioeletricidade. O carvão é uma das doenças mais graves da cana-de-açúcar e ocorrem em canaviais do mundo inteiro. A doença é causada pelo fungo biotrófico Sporisorium scitamineum. Este fungo induz mudanças metabólicas na planta, levando a formação de uma estrutura chamada chicote, onde ocorre a esporogênese. O objetivo desse estudo foi analisar a produção de espécies reativas de oxigênio (EROs), atividade de enzimas antioxidantes e a expressão de genes associados ao metabolismo de EROs em genótipos de cana-açúcar susceptível (IAC66-6) e resistente (SP80-3280). Além disso, este trabalho avaliou a relação entre as enzimas antioxidantes e sensibilidade de S. scitamineum a peróxido de hidrogênio (H2O2) exógeno. Esta tese está apresentada no formato de 2 capítulos (capítulos 2 e 3). No segundo capítulo, os resultados revelaram que ocorreram alterações no sistema antioxidante, bem como na produção de EROs no genótipo resistente, enquanto que poucas mudanças ocorreram no genótipo susceptível inoculado com S. scitamineum. Análises de microscopia revelaram que a germinação de teliósporos e a formação de apressórios de S. scitamineum atrasou durante o início da infeção no genótipo resistente ao carvão, coincidindo com o acúmulo de H2O2. No capítulo 3, os resultados demonstraram que S. scitamineum é altamente resistente a H2O2 exógeno. O fungo crescendo na concentração de 2 mM de H2O2 apresentou um eficiente sistema antioxidante em resposta a produtos secundários do estresse oxidativo. Além disso, quando S. scitamineum foi exposto a 2 mM de H2O2 exógeno, ele pode adquirir uma resposta adaptativa ao H2O2. Os resultados obtidos neste estudo contribuíram para aumentar o entendimento dessa complexa interação entre cana e S. scitamineum e será útil para a compreensão de quais aspectos estão envolvidos na resistência a este fungo. Estas informações são importantes para criar estratégias para o melhoramento de cana a essa doença.
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39

Silva, Susan Ienne da. "Gene da putativa indolpiruvato descarboxilase de Phytomonas: caracterização, arranjo genômico, marcador molecular e origem filogenética." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/42/42135/tde-04062008-123820/.

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O gênero Phytomonas está associado a enfermidades devastadoras em plantações de interesse econômico, enquanto que outros vegetais parasitados não apresentam nenhum dano aparente. A seqüência-consenso de um agrupamento de ESTs de P. serpens determinado anteriormente apresentou alta similaridade com indolpiruvato descarboxilases (IPDCs) de fitobactérias e putativas piruvato/indolpiruvato descarboxilases de Leishmania spp. A enzima IPDC está na via de biossíntese do ácido 3-indolil acético, um dos hormônios vegetais mais importantes. Verificamos que o gene IPDC está presente em diversos isolados de Phytomonas, em múltiplas cópias (cerca de 104 cópias em P. serpens e 200 cópias em P. françai), contíguas e concentradas em uma banda cromossômica. Análises filogenéticas e amplificações por PCR com oligonucleotídeos degenerados apontam o clado Phytomonas-Leishmania como grupo-irmão de IPDCs de fitobactérias, sugerindo um processo de transferência horizontal anterior à separação dos tripanossomatídeos do clado que também inclui Leptomonas, Herpetomonas e Crithidia.
The genus Phytomonas is associated to devastating diseases in commercially important crops, whereas in other plant species no apparent damage is observed. The consensus sequence of one group of ESTs of P. serpens previously determined showed high similarity with indolepyruvate decarboxylases (IPDCs) from phytobacteria and putative pyruvate/indolepyruvate decarboxylases of Leishmania spp. The enzyme ipdC participates in the biosynthetic pathway of the indole-3-acetic acid, one of the most important plant hormones. We found that the IPDC gene is present in several Phytomonas isolates, in multiple copies (about 104 copies in P. serpens and 200 copies in P. françai, in tandem and concentrated in one chromosomal band. The phylogenetic analyses and data of PCR amplifications with degenerated primers point the clade Phytomonas-Leishmania as a sister group of IPDCs of phytobacteria, suggesting a process of horizontal gene transfer prior to the separation of the trypanosomatid clade that also includes Leptomonas, Phytomonas, Herpetomonas, Leishmania and Crithidia.
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40

Falconi, Diego. "Alternative Bekämpfungsmöglichkeiten des Fussfäuleerregers Corticium rolfsii Sacc." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963676466.

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41

Ramiro, Juliana. "Especificidade patogênica e compatibilidade vegetativa entre isolados de Colletotrichum acutatum dos citros e de outros hospedeiros." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/11/11135/tde-10022011-143000/.

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Colletorichum acutatum é o agente causal da Podridão Floral dos Citros (PFC), doença que em determinadas condições ambientais constitui-se em fator limitante à produção citrícola em várias regiões produtoras do mundo. Além da PFC, esse fungo causa antracnose em outros hospedeiros, sendo um dos patógenos que mais acarreta danos em frutíferas tropicais, subtropicais e temperadas no mundo. O trabalho teve como objetivos estudar a especificidade patogênica e compatibilidade vegetativa entre isolados de C. acutatum dos citros e de outros hospedeiros como: goiaba, pimentão, morango e pêssego. Para os estudos de especificidade patogênica, foram realizadas inoculações cruzadas entre isolados de citros e dos outros hospedeiros visando verificar se os diferentes isolados são capazes de causar sintomas de PFC em flores de citros e antracnose em frutos. Foram também obtidos, a partir dos mesmos isolados, mutantes deficientes na absorção de nitrogênio (mutantes nit). Esses foram caracterizados fenotipicamente e pareados a fim de verificar por meio de estudos de compatibilidade vegetativa a capacidade de recombinação entre si, gerando heterocários com patogenicidade alterada. Para verificar a ocorrência de possíveis alterações na patogenicidade dos heterocários formados, foi feita a inoculação dos heterocários e dos isolados parentais nos seus respectivos hospedeiros de origem. Nos ensaios de inoculação cruzada, houve grande variação quanto à patogenicidade dos isolados inoculados. Isolados provenientes de citros e de goiaba causaram lesões em flores de citros, isso demonstra a ausência de especificidade entre isolados dos dois hospedeiros. Porém, isolados provenientes de pimentão, pêssego e morango não foram capazes de causar sintomas em flores de citros o que indica a existência de especificidade desses isolados. Os isolados provenientes dos citros e de outros hospedeiros foram capazes de causar antracnose em goiaba, morango e pêssego, mas apenas os isolados de pimentão causaram antracnose em pimentão. Alguns isolados de citros foram capazes de recombinar entre si e com isolados de goiaba, pimentão e morango. Dos heterocários formados, dois foram caracterizados quanto a sua patogenicidade, Het 3 e Het 5. Como resultado, o heterocário proveniente do isolado de citros com goiaba (Het 5) comportou-se de forma semelhante à um de seus parentais. O heterocário proveniente de citros com pimentão (Het 3), mostrou-se mais agressivo do que seus parentais quando inoculados em pimentão. Com esses estudos pode-se concluir que existe especificidade patogênica entre isolados de C. acutatum de diferentes hospedeiros, entretanto, isolados de diferentes hospedeiros podem recombinar entre si e gerar heterocários com características patogênicas alteradas.
Colletorichum acutatum is the causal agent of postbloom fruit drop (PFD).This disease is a limiting factor for citrus production under specifics environmental conditions in several regions of the world. In addition to the PFD, this fungus causes anthracnose on other hosts. It is one of the pathogens that cause more damage in tropical, subtropical and temperate fruit around the world. This work aimed to study the specificity pathogenic and vegetative compatibility among isolates of C. acutatum from citrus and other hosts: guava, pepper, strawberry and peach. For studies of pathogenic specificity, cross inoculations were performed among isolates from citrus and other hosts in order to verify whether different strains are capable of causing symptoms of PFD in citrus flowers and fruit anthracnose. Furthermore, it was obtained from the same isolates, nitrate-nonutilizing mutants (nit mutants). They were phenotypically characterized and paired to verify, by means of vegetative compatibility studies, the ability of recombination between them, generating heterokaryons with altered pathogenicity. In order to verify the occurrence of possible changes in the pathogenicity of the heterokaryons formed, parental isolates and heterokaryons were inoculated in their respective original hosts. In cross-inoculation tests, there was a great variation in the isolates pathogenicity. Isolates from citrus and guava caused lesions on citrus blossoms; this demonstrates the absence of pathogenic specificity between isolates of the two hosts. However, isolates from pepper, peach and strawberry were unable to induce symptoms on citrus flowers showing the existence of specificity of these isolates. The strains from citrus and other hosts were able to cause anthracnose on guava, strawberry and peach, but only isolates of pepper caused anthracnose on pepper. Some isolates from citrus were able to recombine among themselves and with isolates from guava, peppers and strawberries. From the heterokaryons obtained, two of them had their pathogenicity characterized: Het 3 and Het 5. As a result, the heterokaryon derived from citrus and guava (Het 5) behaved similarly to one of their parental isolates. The heterokaryon derived from citrus and pepper (Het 3) was more aggressive than their parental isolates when inoculated in pepper. With these results we can conclude that there is specificity between pathogenic strains of C. acutatum from different hosts. However, isolates from different hosts can recombine with each other and generate heterokaryons with altered pathogenic characteristics.
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42

Germain, Hugo. "Étude moléculaire du champignon phytopathogène Inonotus tomentosus." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57865.pdf.

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43

Cochard, Clémence. "Régulation fine du système EnvZ/OmpR chez Dickeya dadantii : clef d'une infection réussie." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILS109.

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Tout au long de sa vie, la bactérie doit faire face à de nombreuses variations de l'environnement. Elle doit s'y adapter rapidement et efficacement afin de survivre. Pour cela, elle dispose des phosphorelais, ou systèmes à deux composants qui sont les outils moléculaires majeurs permettant la perception et l'adaptation de l'environnement chez les bactéries. Ils sont composés d'un capteur et d'un régulateur associé. Suite à la perception d'un stimulus, le capteur s'autophosphoryle et transmet le groupement phosphate au régulateur qui va alors moduler l'expression de l'ensemble des gènes cibles, appelé régulon. Durant le processus d'infection, les bactéries pathogènes doivent faire face à de multiples stress. Ainsi est retrouvé un nombre important de ces systèmes chez de nombreuses bactéries pathogènes comme notre modèle d'étude Dickeya dadantii. Responsable de la maladie de la pourriture molle, D. dadantii est une entérobactérie phytopathogène à large spectre d'hôte. Elle dispose d'une batterie de 32 phosphorelais pour affronter les défenses de l'hôte et les stress généraux de carences nutritionnelles ou des variations physico-chimique de l'environnement.Dans un premier temps, cette étude se focalise sur l'un d'entre eux, le système EnvZ/OmpR. Mes travaux montrent dans un premier temps que le pH dans la plante reste acide durant l'infection. Cependant, malgré une activation du système par le pH acide, il n'est pas activé durant ce processus. Pour comprendre la raison de cette incohérence, le régulon du système a été étudié. Il a alors été découvert que durant l'émergence du genre Dickeya, le gène ompF, codant la porine du même nom, a été dupliqué. De façon intéressante, l'expression d'ompF est constitutive tandis que celle d'ompF2, le gène dupliqué, est soumise au niveau de phosphorylation d'OmpR. L'expression de cette seconde porine est également délétère à l'infection. Ainsi, durant l'infection, l'activation d'EnvZ/OmpR est contrecarrée par la perception de molécule de défense de l'hôte afin d'éviter l'expression d'ompF2 et permettre un bon déroulement de la virulence.Dans un second temps, a été réalisée lors de mes travaux une étude globale de l'importance de chaque phosphorelais sur la virulence de D. dadantii. Les premiers résultats montrent que seuls 6 systèmes sont impliqués dans la virulence. Le nombre et la complexité des stress rencontrés par les bactéries pathogènes ne semblent pas en accord avec ce faible nombre. La baisse de la quantité de bactéries inoculées a permis d'affiner la détection des systèmes participant à la virulence, qui se comptent désormais au nombre de 12. Enfin, l'ensemble de ces résultats indiquent l'importance d'une régulation fine de l'activation d'un phosphorelais car EnvZ/OmpR doit être activé pour l'infection mais que cette activation doit être fermement contrôlée au risque d'avoir des effets néfastes sur la virulence
Throughout their life, the bacteria must confront numerous environmental variations. They must adapt rapidly and effectively to ensure their survival. To accomplish this, they possess phosphorelays, or two-component systems, which are the major molecular tools enabling perception and adaptation to the environment in bacteria. These phosphorelays consist of a sensor and an associated regulator. Following the perception of a stimulus, the sensor autophosphorylates and transmits the phosphate group to the regulator, which then modulates the expression of the entire target gene set, known as a regulon. During the infection process, pathogenic bacteria must deal with multiple stresses. A significant number of these systems are found in various pathogenic bacteria, such as our study model Dickeya dadantii. Responsible for soft rot disease, D. dadantii is a wide-host-range phytopathogenic enterobacterium. It possesses a battery of 32 phosphorelays to deal with host defenses and the general stresses of nutritional deficiencies or physicochemical variations in the environment.First this study focuses on one of them, the EnvZ/OmpR system. My work initially shows that the pH in the plant remains acidic during infection. However, despite activation of the system by acidic pH, it is not activated during this process. To understand the reason for this inconsistency, the system's regulon was studied. It was then discovered that during the emergence of the Dickeya genus, the ompF gene, encoding the porin of the same name, was duplicated. Interestingly, the expression of ompF is constitutive, whereas that of ompF2, the duplicated gene, which is dependent on OmpR phosphorylation levels. The expression of this second porin is also detrimental to infection. Thus, during infection, the activation of EnvZ/OmpR is counteracted by the perception of host defense molecules to prevent the expression of ompF2 and enable proper virulence progression.In a second phase, a comprehensive study of the importance of each phosphorelay in D. dadantii's virulence was conducted in my work. The initial results show that only 6 systems are involved in virulence. The number and complexity of stresses encountered by pathogenic bacteria do not seem to align with this low number. Reducing the quantity of inoculated bacteria allowed for a more precise detection of the systems contributing to virulence, which now totals 12. Overall, these results indicate the significance of finely regulating the activity of a phosphorelay, as EnvZ/OmpR must be activated for infection, but this activation must be strongly controlled to avoid detrimental effects on virulence
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44

Gay, Elise. "Dissection transcriptomique de la biologie de Leptosphaeria maculans lors de ses interactions avec son hôte (le colza) et avec un membre du complexe d'espèces, Leptosphaeria biglobosa Large-scale transcriptomics to dissect two years of the life of a fungal phytopathogen interacting with its host plant." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASB015.

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Leptosphaeria maculans est un champignon pathogène responsable de la nécrose du collet chez le colza. Son cycle de vie est long et complexe car composé d’une succession d’étapes de colonisation asymptomatiques puis nécrotiques des différents tissus de l’hôte, depuis la colonisation hémibiotrophe des feuilles à l’automne à la nécrose du collet au printemps. Après ces phases infectieuses dans des tissus végétaux vivants, L. maculans vit en tant que saprophyte dans les résidus de culture. Jusqu’ici, l’étude des déterminants moléculaires de la pathogénie chez L. maculans s’est concentrée sur l’analyse d’une classe spécifique de gènes, codant pour des « effecteurs », et cela durant une seule partie du cycle : l’infection précoce des feuilles. A l’heure actuelle il n’y a pas de vue d’ensemble des gènes impliqués dans la pathogénie durant tout le cycle infectieux. Aussi, le cycle de vie de L. maculans est intimement lié à celui de Leptosphaeria biglobosa, une espèce proche mais moins pathogène. L. biglobosa coinfecte le colza avec L. maculans durant tout leur cycle de vie, mais son impact sur L. maculans est mal connu. Récemment, 420 échantillons biologiques, collectés durant toutes les étapes du cycle de vie de L. maculans, ont été séquencés par RNA-Seq. Ils incluent des conditions in vitro et in planta, à la fois dans un environnement contrôlé (en coinfection ou non avec L. biglobosa) et en conditions d’infection naturelle. Les objectifs de ma thèse étaient : (i) d’identifier le plus exhaustivement possible, par des approches transcriptomiques, les gènes induits chez L. maculans durant l’entièreté de son cycle infectieux et (ii) de déterminer l’impact de l’interaction biotique avec L. biglobosa. J’ai d’abord montré que 9 % des gènes prédits chez L. maculans sont induits spécifiquement lors de l’infection. Ils sont répartis en huit vagues d’expression redécoupant le cycle tel que décrit dans la littérature et révèlent, pour certains stades, une décomposition transcriptomique encore plus complexe, qui dépend de l’organe colonisé ou du type trophique adopté par le champignon. Je démontre aussi l’importance de la régulation épigénétique puisque toutes les vagues d’expression sont enrichies en gènes localisés dans un environnement génomique de type hétérochromatinien. Lorsque le troisième partenaire, L. biglobosa, entre en jeu en début de cycle, l'expression des gènes chez L. maculans stagne et est accompagnée de l’arrêt de la colonisation. Cet effet inhibiteur est cependant restreint à des conditions de co-inoculations rarement observées lors des infections naturelles. Mon projet de thèse constitue ainsi une première description transcriptomique du cycle de vie de L. maculans dans son intégralité et en interaction avec son environnement biotique
Leptosphaeria maculans is a pathogenic fungus responsible for the stem canker disease of oilseed rape. Its life cycle is long and complex and is composed of a succession of asymptomatic and necrotic colonisation stages of the host tissues, from the hemibiotrophic colonisation of leaves in autumn to the stem canker development in spring. After these infectious stages on living plant tissue, L. maculans survives as a saprophyte within crop residues. So far, the study of the molecular determinants of L. maculans pathogenesis was focused on a specific class of genes, encoding "effector" proteins, and focused on the early infection on leaves. At present there is no global view of the genes involved in the pathogenesis during the entire infection cycle. In addition, the life cycle of L. maculans is closely related to that of Leptosphaeria biglobosa, a closely related, less pathogenic species. L. biglobosa co-infects the oilseed rape plants along with L. maculans throughout the fungal life cycles, but its impact on L. maculans is poorly understood. Recently, 420 biological samples, collected during all stages of the life cycle of L. maculans, have been sequenced by RNA-Seq, including in vitro and in planta conditions, both in controlled environments (whether or not co-infected with L. biglobosa) or under natural infection. The objectives of my thesis were: (i) to identify as exhaustively as possible, using tanscriptomic approaches, the genes induced in L. maculans during its entire infectious cycle and, (ii) to determine the impact of the biotic interaction with L. biglobosa. I first showed that 9% of the predicted genes in L. maculans are induced specifically during infection. These are clustered into eight waves of expression, outlining the cycle as described in the literature and revealing, for some stages, a more complex transcriptomic subdivision, depending on the organ infected or on the lifestyle adopted by the fungus. I also demonstrate the importance of epigenetic regulation since all the waves of expression are enriched with genes located in a heterochromatin environment. When the third partner, L. biglobosa, coinfects the leaves at the beginning of the cycle, the gene expression in L. maculans stagnates and the plant colonisation by L. maculans is inhibited. However, this inhibitory effect is conditioned by strict conditions of co-inoculations, rarely observed during natural infections. My thesis project thus constitutes a first transcriptomic description of the life cycle of L. maculans in its entirety and in interaction with its biotic environment
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45

Mugnier, Marie-Ange. "Rna 3 du virus de la mosaique de la luzerne (almv) : obtention d'une copie cdna complete et etude conformationnelle de la region 5' du rna 3 de differentes souches." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13160.

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Synthese d'une copie complete d'adn complementaire qui est ensuite clone dans un vecteur d'expression pgemi. La comparaison de la sequence des cdna avec celle de l'arn 3 met en evidence une duplication dans la region 5' non codante, d'une sequence de 56 nucleotides qui constitue la difference majeure entre ces 2 sequences. La structure primaire de la region 5' non codante a ete examinee dans l'arn 3 de 3 souches du virus. Cette etude est completee par une analyse conformationnelle, en utilisant des sondes chimiques (dms) et enzymatique (v1 et s1)
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46

Meyer, Michel. "Contribution a l'etude de la structure et de l'organisation du rna-2 (isolat s) et des rna satellites de 5 isolats du tbrv." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13091.

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La sequence de l'arn-2 de l'isolat s comporte une seule phase de lecture ouverte qui correspond a une proteine de p. M. 150 k. La proteine de la coque est localisee dans la region c terminale de la proteine 150 k. Une proteine "de diffusion" se situerait en amont de la proteine de la capside. Les sequences des arn satellites issus d'isolats appartenant aux serotypes s (s et l) et g (g, e et c) comportent toutes une seule phase de lecture ouverte correspondant a une proteine de 48 k. La comparaison des sequences permet de distinguer 2 groupes: les arn s et l d'une part, les arn g, e et c, d'autre part. A l'interieur de chaque groupe, les arn presentent plus de 90% d'homologie de sequence tandis que 63% des nucleotides sont communs aux 5 arn etudies
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47

Mercier, Alex. "Déterminants génomiques de la spécialisation à l’hôte chez le champignon phytopathogène polyphage Botrytis cinerea." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS442.

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Les champignons phytopathogènes sont des parasites majeurs des espèces végétales, autant naturelles que domestiquées. Botrytis cinerea, l’agent de la pourriture grise, en infecte plus de 1400 et est ainsi considéré comme un pathogène généraliste. Pourtant, des données récentes ont mis en évidence une structure des populations liée à leur hôte d’origine. Cette observation soulève l’hypothèse d’une spécialisation à l’hôte, à l’œuvre chez une espèce généraliste. Ce modèle d’étude pourrait permettre de faire avancer la connaissance des mécanismes évolutifs en jeu dans la divergence précoce des populations et la formation de nouvelles espèces fongiques. Cette thèse de doctorat a pour objectifs : (i) de démontrer formellement la spécialisation à l’hôte dans les populations de B. cinerea et d’en déterminer la magnitude et (ii) d’identifier les déterminants génomiques de cette spécialisation. Ainsi j’ai étudié la structure des populations par l’analyse de microsatellites d’un échantillon de 683 isolats, que nous avons corrélé à des tests de pathogénicité croisés sur différents hôtes. Ces travaux ont permis de mettre en évidence la spécialisation de B. cinerea aux hôtes tomate et vigne. En complément de ces lignées sélectionnées, l’espère Botrytis cinerea est constituée d’individus généralistes capables de coloniser les autres hôtes. Des méthodes d’inférence de structure et de généalogies sur des données de polymorphisme issues du séquençage de 32 individus nous ont permis de mieux définir la structure des populations ainsi que d’identifier une lignée spécialisée à la tomate. Enfin, des tests de McDonald-Kreitman et des méthodes de scans génomiques pour détecter des balayages sélectifs ont permis de mettre en évidence des gènes soumis à la sélection divergente entre les populations spécialisées, révélant de possibles déterminants de cette spécialisation. Ces travaux sont ainsi une base pour la validation de plusieurs gènes impliqués dans la pathogénicité hôte-spécifique de B. cinerea, et ouvrent la voie à des améliorations de la gestion du réservoir d’hôtes et des pratiques culturales contre la pourriture grise
Phytopathogenic fungi are major parasites to wild or domesticated plant species. The grey mold fungus, Botrytis cinerea, infects more than 1400 plant species and thus is considered a broad generalist. However, recent data have revealed population structure correlated to the host of origin of isolates. This observation raises the hypothesis of ongoing host specialization in a generalist species. Studying this question could greatly deepen our theoretical knowledge of the evolutionary mechanisms involved in the early stages of population divergence and subsequent speciation. This thesis aims (i) to formally demonstrate the host specialization in B. cinerea’s populations and determine its magnitude, and (ii) to identify the genomic determinants of this specialization. Thus, I studied population structure based on 683 isolates characterized using microsatellite markers. We compared the inferred genetic structure with variations in aggressiveness measured through cross-pathogenicity tests on multiple hosts. These experiments and analyses confirmed the specialization of B. cinerea to tomato and grapevine hosts. Besides these specialized lineages, the species B. cinerea is composed of generalist individuals capable of infecting multiple hosts. I sequenced the whole genome of 32 individuals and characterized nucleotide polymorphism. Structure inference and genomic genealogy methods allowed us to more accurately define the population structure and identify a lineage specialized on tomato. Lastly, McDonald-Kreitman tests and genomic scans methods allowed the identification of genes under divergent natural selection between populations, revealing possible genomic determinants of specialization. This work can serve as foundation for the validation of multiple genes involved in host-specific pathogenicity of B. cinerea, and pave the way for the implementation of efficient strategies for managing pathogen reservoirs and new agricultural practices for controlling grey mold
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48

Ulrich, Kristina. "Molekulargenetische Differenzierung phytopathogener Pilze des Gaeumannomyces/Phialophora-Komplexes /." Jena, 2001. http://www.db-thueringen.de/servlets/DerivateServlet/Derivate-1184/Diss-Ulrich.pdf.

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49

Holmes, Keith Andrew. "Antagonism of phytopathogenic fungi by Pythium oligandrum Drechsler." Thesis, Manchester Metropolitan University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336555.

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50

Félix, Carina Rafaela Faria da Costa. "Lasiodiplodia theobromae: a phytopathogenic fungus that infect humans." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10469.

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Mestrado em Biologia Aplicada
Lasiodiplodia theobromae é um fungo fitopatogénico responsável por inúmeras doenças em variadas plantas. Embora este fungo seja tipicamente de regiões tropicais e subtropicais, também ocorre em climas mais frios. L. theobromae tem também sido descrito como oportunista em humanos, causando infeções com diferentes níveis de gravidade. Apresenta, assim, uma grande adaptabilidade a diferentes ambientes, sendo capaz de utilizar os seus mecanismos de virulência numa ampla gama de temperaturas. O objetivo desta investigação é caracterizar o crescimento de dois isolados - um isolado ambiental, CAA019 e um isolado clínico, CBS339.90 - a diferentes temperaturas (temperatura ambiente e temperatura do corpo humano). Tendo em conta a relevância deste organismo como fitopatogénico assim como a sua crescente importância como oportunista de humanos, este estudo poderá ter uma grande relevância para agricultura, bem como para a saúde humana. As condições ótimas de cultivo destes isolados foram determinadas: o meio de cultura Potato Dextrose Agar como melhor meio para o cultivo e a temperatura de 30ºC como sendo a temperatura ótima de crescimento para ambos os isolados. Verificou-se ainda que a presença de luz continua tem um efeito positivo no crescimento de L. theobromae e que o seu crescimento máximo é atingido entre as 96 horas e as 120 horas de incubação. Verificou-se ainda que ambos os isolados expressam proteínas extracelulares de um modo dependente da temperatura, assim como do isolado. Por último, foi possível verificar que ambos os isolados produzem moléculas extracelulares com propriedades citotóxicas numa linhagem de células Vero (células de rins de macaco verde africano) verificando-se que ambos os isolados são citotóxicos nestas células. As maiores perdas de viabilidade são atingidas às temperaturas de 25ºC e 30ºC para o isolado ambiental e a 30ºC e 37ºC para o isolado clínico.
Lasiodiplodia theobromae is a phytopathogenic fungus responsible for a countless number of diseases in various plants. Although this fungus is typically from tropical and subtropical regions, it can also occur in colder climates. It has been also described as an opportunist in humans, causing infections of different levels of severity. L. theobromae thus presents a great capacity of adaptation to different environments, being able to use its virulence mechanisms in a wide range of temperatures. The aim of this investigation is to characterize two different isolates – an environmental isolate, CAA019, and a clinical isolate, CBS339.90 – at different temperatures (environmental temperature and human body temperature). Due to the relevance of this species as a phytopathogenic agent, as well as its growing importance as an opportunist pathogen in humans, this study may reveal itself as being extremely relevant both to agriculture and to human health. The optimal growth conditions of these isolates have been determined: Potato Dextrose Agar is the best culture medium and the temperature of 30ºC the optimal growth temperature for both isolates. It has also been shown that continuous light has a positive effect in the growth of L. theobromae and that this fungus reaches its maximum growth between 96 hours and 120 hours of incubation. Also, a differential extracellular protein expression has been detected, depending both on the temperature of growth and on the isolate. Lastly, it was possible to verify that both isolates produce extracellular molecules with cytotoxic properties against a Vero cell line (cells from the kidneys of African Green Monkey), thus concluding that both isolates are cytotoxic for this cells. Lowest values of cell viability have been achieved for the temperatures of 25ºC and 30ºC in the case of the environmental isolate, and for the temperatures of 30ºC and 37ºC in the case of the clinical isolate suggesting that there may be some specificity of the isolate towards its host.
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