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Mekala, Vijaya Krishna Wysocka-Diller Joanna. "Isolation and characterization of Scarecrow suppressor mutants in Arabidopsis thaliana." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/FALL/Biological_Sciences/Thesis/Mekala_Vijaya_18.pdf.
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Albhilal, Waleed Sulaiman. "The Arabidopsis thaliana heat shock transcription factor A1b transcriptional regulatory network." Thesis, University of Essex, 2015. http://repository.essex.ac.uk/15732/.
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Plants as sessile organisms have adapted highly sophisticated cellular processes to cope with environmental stress conditions, which include the initiation of complex transcriptional regulatory circuits. The heat shock transcription factors (HSFs) have been shown to be central regulators of plant responses to abiotic and biotic stress conditions. However, the extremely high multiplicity in plant HSF families compared to those of other kingdoms and their unique expression patterns and structures suggest that some of them might have evolved to become major regulators of other non-stress related processes. Arabidopsis thaliana HSFA1b (AtHSFA1b) has been shown to be a major regulator of various forms of plant responses to abiotic and biotic stresses. However, it has also been suggested that overexpression of AtHSFA1b results in a subtle developmental effect in Arabidopsis thaliana and Brassica napus in the form of increased seed yield and harvest index. Through genome-wide mapping of the AtHSFA1b binding profile in the Arabidopsis thaliana genome, monitoring changes in the AtHSFA1b-regulated-transcriptome, and functional analysis of AtHSFA1b in Saccharomyces cerevisiae under non-stress and heat stress conditions, this study provides evidence of the association of AtHSFA1b with plant general developmental processes. Furthermore, the outcome of this research shows that AtHSFA1b controls a transcriptional regulatory network operating in a hierarchical manner. However, in an agreement with a previously suggested model, the results from this study demonstrate that the involvement of AtHSFA1b in the regulation of heat stress response in Arabidopsis thaliana is possibly limited to the immediate and very early phases of heat stress response which also results in a collapse in its transcriptional network which seems to be accompanied by a general shutdown in plant growth and development.
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Doherty, Colleen J. "Transcriptional networks involved in response to low temperature stress in Arabidopsis thaliana." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (Ph. D.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2008.Title from PDF t.p. (viewed on July 10, 2009) Includes bibliographical references. Also issued in print.
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Yuan, Kun Wysocka-Diller Joanna Singh Narendra K. "Functional and genetic analysis of plant transcription factors involved in the plant growth under various environmental conditions." Auburn, Ala, 2008. http://repo.lib.auburn.edu/2007%20Fall%20Dissertations/Yuan_Kun_37.pdf.
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Larkin, Robert M. "Analysis of nuclear DNA-dependent RNA polymerase subunits and tata-binding protein from plants /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9821341.
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Abeysinghe, Arachchige Jayami Kaushalya Abeysinghe. "Mechanism of WRKY transcription factors-mediated defense and heterosis in Arabidopsis polyploids." HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/596.
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WRKY transcription factors (TFs) belong to a large family of regulatory proteins in plants that modulate many plant processes. Extensive studies have been conducted on WRKY-mediated defense response in Arabidopsis thaliana and many crop species. This study aims to investigate the potential roles and contributions of WRKY TFs regulation in improving defense response in the resynthesized Arabidopsis allotetraploids (Arabidopsis suecica) from two related autotetraploid progenitors, Arabidopsis thaliana (At4) and Arabidopsis arenosa (Aa). Upon infection by Pseudomonas syringae (Pst), the allotetraploids has showed enhanced resistance against the pathogen when compared to the parents. Rapid induction of WRKY18, WRKY40, WRKY38, WRKY53, WRKY6; MAP kinase pathway related genes, WRKY33, PAD3; SA-pathway related genes, ICS1, EDS1, PBS3, MYB31; was evident in response to Pst and salicylic acid treatment in the allotetraploids. Cleaved amplified polymorphic sequences analysis further revealed that the AtWRKY18, AaWRKY40, AtWRKY33, and AtWRKY60 alleles expressed at higher levels when compared to their respective homoeologs in the allotetraploids, suggesting potential altered protein-protein interaction networks in the hybrids. Therefore, a split-luciferase complementation assay was used to characterize and quantify protein-protein interaction among these homoeologous WRKYs in the allotetraploids. Results showed that preferential protein-protein interactions exist for the cis-interacting AtWRKY18/AtWRKY18 homodimer or trans-interacting AtWRKY18/AaWRKY40 heterodimer when compared to the respective interacting complexes. In addition, differential affinities of WRKY18 and WRKY40 homo- and hetero- dimers toward the W-boxes at the WRKY60 promoter were observed. In the allotetraploids, PR1 expression was repressed under basal state when compared to the progenitors. Although PR1 is expressed at a higher level in A. thaliana, its expression fold change was higher and faster in the all otetraploids upon salicylic acid treatment. Transient expression of WRKY18 or WRKY40 homodimer in various combinations induced differential expression of PR1 gene in their respective wrky18 and wrky40 Arabidopsis thaliana mutants. In contrast, similar PR1 induction by homodimer in various combinations was observed when they were transiently expressed in the allotetraploids. In addition, transgenic AtWRKY18 overexpression plant displayed enhanced disease resistance against Pst when compared to AaWRKY18 overexpression lines. Such enhanced disease resistance was found to associate with the higher expression of PR1 and PR2 in AtWRKY18 transgenic lines. Moreover, differential Pst-induced expression of the direct targets (ICS1, EDS1 and PBS3) of WRKY18 in the Arabidopsis AtWRKY18 and AaWRKY18 overexpressors supported a biological difference between the At and Aa homodimers in mediating the targets regulation, thus contributing to the difference in disease responses. Overall, our findings suggested that the rapid differential alleles expression and altered protein-protein or protein-DNA interactions of WRKY transcription factors could contribute to the improved defense in the allotetraploids, providing a molecular basis of for heterotic phenotype development in hybrids.
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Kaveh, Rashid. "TRANSCRIPTIONAL RESPONSES OF SOYBEAN (GLYCINE MAX) AND THALE CRESS (ARABIDOPSIS THALIANA) PLANTS EXPOSED TO DIFFERENT CLASSES OF ENVIRONMENTAL CONTAMINANTS." Diss., Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/303672.
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Civil EngineeringPh.D.
Plants are exposed to various environmental contaminants through irrigation with reclamation water and land application of municipal biosolids. Plants have been shown to take up contaminants from soil and groundwater, and to some extent, metabolize them in their tissues. These mechanisms have potential important implications for the environment and human health. First, as plants constitute the basis of the terrestrial food chain, accumulation of toxic chemicals or their metabolites inside plant tissues may lead to contamination of animals and humans. Second, the recognition of the capability of plants to take up and metabolize contaminants has led to the development of a plant-based remediation technology, referred to as phytoremediation. Phytoremediation is defined as the use of higher plants for the removal of environmental contaminants from soil and groundwater. Although phytoremediation is conceptually attractive as a green, environmental-friendly technology, the metabolism of xenobiotic compounds by plants is often slow and incomplete, possibly resulting in the accumulation of toxic pollutants and/or their metabolites inside plant tissues. Without further detoxification, phytoremediation may result in pollution transfer, potentially threatening the food chain, and eventually humans. Gaining further knowledge about the fate of environmental contaminants inside plant tissues is therefore of paramount importance for conducting environmental risk assessment and enhancing the efficiency of phytoremediation applications. It's an attractive concept today to cultivate plants on contaminated lands, in order to combine the benefits of phytoremediation with plant-based biofuel production. Unlike conventional plant bioenergy production, plant biomass grown on marginal contaminated soil will not compete with land for food production. However, the effect of contaminants on the plant biomass and bioenergy feedstock yield have received little attention. Molecular biology techniques, such as high-throughput gene expression analysis, constitute powerful tools to understand the molecular bases of the plant metabolism and response to environmental contaminants. The objective of this thesis is to understand the physiological and transcriptional responses of two model plants, thale cress (Arabidopsis thaliana) and soybean (Glycine max), exposed to various classes of contaminants, including silver nanoparticles (AgNPs), pharmaceuticals (zanamivir - ZAN and oseltamivir phosphate - OSP), explosives (2,4,6-trinitrotoluene - TNT), and polychlorinated biphenyls (PCBs). Detection of the contaminants inside plants tissues was performed using advance analytical methods, including inductively-coupled plasma - mass spectrometry (ICP-MS), gas-chromatography - mass spectrometry (GC-MS), and liquid-chromatography (LC-MS). The effects of contaminants on plants were assessed by recording various plant metrics, including biomass, root and shoot length, and soybean production. The transcriptional response of plants to exposure to selected contaminants (AgNPs, OSP, and ZAN) was investigated using whole-genome expression microarrays and reverse-transcription real-time (quantitative) PCR (RT-qPCR). In the first experimental phase of this research, the effects of AgNPs and soluble silver (Ag+) on A. thaliana plants were investigated. AgNPs are widely used nanomaterials, which have raised environmental concerns because of their toxicity to most living organisms, including plants. Exposure of hydroponic A. thaliana plants for 14 days to 20-nm AgNPs resulted in a slight increase of the biomass at low concentrations (1.0 and 2.5 mg / L) and a significant decrease of the biomass at higher concentrations (5.0 to 100 mg / L). Exposure to Ag+ for 14 days resulted in a significant reduction of the biomass after 14 days at concentration at and above 5.0 mg / L. Genome-wide expression microarrays revealed that exposure of A. thaliana to AgNPs and Ag+ at the concentration of 5 mg / L for 14 days resulted in differential expression of many genes involved in the plant response to stress and to biotic and abiotic stimuli. Although distinct gene expression patterns developed upon exposure to AgNPs and Ag+, a significant overlap of differentially expressed genes was observed between the two treatments, suggesting that AgNP-induced stress originated partly from silver toxicity and partly from nanoparticle-specific effects. In the second experimental phase of this research, the effects of the antiviral drugs, OSP and ZAN, on A. thaliana were investigated using an approach similar as the one described above. OSP and ZAN are pharmaceutical drugs that currently constitute the last line of defense against influenza infection. These drugs have been widely detected in wastewater effluents, especially during the influenza season, and they have the potential to contaminate agricultural plants through irrigation and land application of biosolids. Exposure of A. thaliana to OSP showed a significant decrease in the plants biomass at the concentrations of 20 and 100 mg / L, although no significant effect on the biomass was recorded upon exposure to ZAN (up to 100 mg / L), suggesting low acute toxicity of these compounds on plants. On the other hand, Arabidopsis exposure to OSP and ZAN at 20 mg / L resulted in significant transcriptional changes, including up- and down-regulation of many genes involved in the plant response to oxidative stresses and response to stimuli. Comparison with an Arabidopsis gene expression database (Genevestigator), revealed that many genes significantly up- and down-regulated by exposure to OSP and/or ZAN were similarly affected by exposure to biotic and abiotic stresses, toxic chemicals, and hormonal stimuli, suggesting that OSP and ZAN have negative chronic effects on plant health. The third experimental phase of this thesis focuses on the effects of two important persistent pollutants, TNT and PCBs, on the growth of soybean plants, with the objective of assessing the potential of using energy crops for the combined benefit of land remediation and biofuel (biodiesel) production. Explosives, such as TNT, are common toxic contaminants frequently observed at explosive manufacturing sites and military training ranges. PCBs are ubiquitous and toxic contaminants that are found in virtually every compartment of the environment. Short-term growth inhibition tests conducted with TNT and selected PCBs (e.g., 2,4'-dichlorobiphenyl - 2,4'-DCB) showed that these compounds exerted no or mild observable effects on plant growth even when applied at very high concentrations (i.e., 100 to 250 mg / kg soil, respectively). Analysis of TNT and 2,4'-DCB in exposed plant tissues showed average concentrations of 30 - 40 ng/g of TNT and 9,000 to 17,000 ng/g of 2,4'-DCB, which is consistent with biotransformation of TNT inside plant tissues. On the other hand, long-term exposure experiments show that exposure to TNT significantly affected soybean growth and production of bean in TNT-exposed plants (25 - 50 mg / kg soil). Exposure to TNT resulted in a significant decrease of the biomass of harvested beans after 120 days, which may have important consequences on the yield of biodiesel obtained from plants grown on contaminated land. Soybean were then exposed to 2,4'-DCB and its major transformation products, 4-OH-2,4'-DCB). Although high concentrations of the parent PCB (100 and 200 mg / kg) resulted in significant decrease of the biomass, high concentrations of the OH-metabolite resulted in increase of the plant biomass. Future research work will include the determination of the molecular bases of the effects - both positive and negative - of TNT, PCBs, and OH-PCBs on soybean plants and beans.
Temple University--Theses
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Salla, i. Martret Mercè. "Control hormonal i genètic de la síndrome de fugida de l’ombra en "Arabidopsis thaliana"." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/84091.
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Les plantes disposen d’una sèrie de fotoreceptors que informen de manera contínua sobre les característiques lumíniques ambientals, permetent optimitzar el seu creixement i desenvolupament. Els fitocroms són els fotoreceptors millor caracteritzats, que absorbeixen en la regió del roig (R) i del roig llunyà (FR). De tots els processos que regulen, la síndrome de fugida de l’ombra o SAS (de l’anglès shade avoidance syndrome) és probablement el més important en plantes crescudes en llum. La SAS es refereix al conjunt de respostes induïdes en plantes creixent en alta densitat o sota una coberta vegetal. Malgrat la complexitat d’aquestes respostes, la SAS s’indueix per un sol senyal ambiental, que és la disminució de la raó R:FR, la percepció de la qual pels fitocroms inicia una xarxa transcripcional. En el nostre laboratori ens hem centrat en un grup de gens l’expressió dels quals està ràpida i directament alterada per llum de baixa raó R:FR o ombra simulada, anomenant-los gens PAR (de l’anglès phytochrome rapidly regulated). En la present tesi s’ha aprofundit en l’estudi de la cadena de transducció de la senyal en la SAS en Arabidopsis thaliana, emfatitzant en els punts de connexió amb les rutes transcripcionals hormonals.
Resultats d’aquesta tesi, que es complementen amb d’altres obtinguts anteriorment en el grup, demostren que un dels gens PAR, ATHB4, que codifica per un factor de transcripció del tipus Homeo-Domain Leucine-Zipper (HD-ZIP subfamília II), té un paper en la senyalització de la SAS com a un modulador complex en aquestes respostes, involucrant diferents hormones en la seva acció. Per dur-ho a terme es van fer aproximacions amb mutants de guany de funció (de sobreexpressió constitutiva amb activitat induïble) i de pèrdua de funció. Particularment s’ha caracteritzat fisiològica, molecular i histològicament el doble mutant athb4hat3, resultats que mostren una disminució de la resposta a diferents estímuls (hormonals i de llum) d’aquest doble mutant. També hem investigat el paper d’ATHB4 com a regulador del desenvolupament vegetal coactuant amb HAT3 a través d’estudis histològics i moleculars del doble mutant ahb4hat3, el qual mostra fortes alteracions morfològiques relacionades amb la polaritat en el desenvolupament.
Per aprofundir, hem investigat el paper dels quatre membres més propers (pertanyents a HD-Zip II) en les respostes SAS i al control hormonal a nivell molecular i/o fisiològic utilitzant línies de sobreexpressió i de pèrdua de funció, englobant els resultats en un possible mòdul regulador de determinades respostes de la planta.
Aquesta hipòtesi ve recolzada pels resultats que els identifiquen com a gens reguladors complexos d’aquesta resposta.
En paral•lel, hem estudiat l’expressió de SAUR15, un gen de resposta a auxines, BRs i ombra simulada; el qual està regulada per ATHB4 de manera directa. S’han identificat elements E-box i AREs, i s’ha estudiat el seu paper en les respostes a ombra i a hormones. Els nostres resultats mostren que aquests elements no són imprescindibles per a la correcta resposta del promotor als estímuls aplicats.
Una altra aproximació fou l’estudi de la resposta SAS de mutants específics de brassinosteroides i auxines (els quals estan relacionats amb la modulació de l’expressió de SAUR15), on resultats de la tesi suggereixen una connexió entre BRs i la resposta a ombra simulada.
Els resultats obtinguts en quant a components moleculars involucrats en les respostes SAS provenen de l’anàlisi de tota la plàntula sencera. Donat que els llocs de percepció de la llum i de l’acció poden estar físicament separats a la planta, vam estudiar la importància de la comunicació a llarga distància per entendre com la planta creix i es desenvolupa regulada per la llum durant la SAS, obtenint com a resultat que tant els cotilèdons com el meristem apical són importants, però no imprescindibles, en aquesta resposta."Hormonal and genetic control of shade avoidance syndrome in Arabidopsis thaliana " Plants sense the presence of competing neighboring vegetation as a change in light quality: i.e. they sense the reduced ratio of red light to far-red light. The responses to shade are generally referred to as the shade avoidance syndrome (SAS), and involve various developmental changes intended to outgrow or outcompete the neighboring plants. In this thesis we analyzed the function of ATHB4, a gene encoding a homeodomain-leucine zipper (HD-Zip) class-II transcription factor from Arabidopsis thaliana, the expression of which is rapidly and directly upregulated after proximity perception by the phytochrome photoreceptors. Our results, altogether with previous studies in my group, suggest that some members of this small gene subfamily can modulate SAS responses by controlling auxin, brassinosteroid and gibberellin molecular and/or physiological responsiveness. In particular, we propose ATHB4 as a new shade signaling component that participates in integrating shade perception and hormone-mediated growth. To get this conclusion we perform experiments with overexpression and loss-of-function lines. We specially characterized double mutant athb4hat3, which has strong morphological alterations, and which let us find a connection point between light and development concerning polarity.
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Finke, Andreas [Verfasser], Gunter [Akademischer Betreuer] Reuter, Michael Florian [Akademischer Betreuer] Mette, and Scheid Ortrun [Akademischer Betreuer] Mittelsten. "The genetic characterization of RNA-directed transcriptional gene silencing in Arabidopsis thaliana / Andreas Finke. Betreuer: Gunter Reuter ; Michael Florian Mette ; Ortrun Mittelsten Scheid." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2013. http://d-nb.info/1058587161/34.
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Koumis, Philippou [Verfasser], George [Akademischer Betreuer] Coupland, Ute [Akademischer Betreuer] Hoecker, and Ulf-Ingo [Akademischer Betreuer] Fluegge. "Identification and Genetic Analysis of Metabolic – Transcriptional Interactions within the Circadian System of Arabidopsis thaliana / Philippou Koumis. Gutachter: George Coupland ; Ute Hoecker ; Ulf-Ingo Fluegge." Köln : Universitäts- und Stadtbibliothek Köln, 2015. http://d-nb.info/1074243234/34.
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Lageix, Sébastien. "Impact d'un stress viral sur la transcription des SINE d'Arabidopsis thaliana et influence de l'ARN SINE sur la kinase GCN2." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00731032.
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Chez les mammifères, l'infection par l'adénovirus conduit à l'activation de la transcription de certains éléments SINE Alu. Il s'agit d'un mécanisme conservé car il est observé avec d'autres familles de virus. Adénovirus code pour une protéine, E1A qui est capable d'interagir avec la protéine Rétinoblastome (RB). Cette interaction provoque l'inactivation de RB ce qui provoque probablement l'activation transcriptionelle des éléments Alu. Ainsi, chez les mammifères, certaines protéines virales agissent négativement sur RB ce qui a pour conséquence de déréguler le cycle cellulaire, la transcription pol III de manière générale et la transcription des éléments SINE en particulier. Chez les plantes, l'activation de la transcription des éléments SINE à la suite d'un stress comme l'infection virale reste à démontrer. Cependant, le virus FBNYV possède au sein de son génome une protéine, CLINK, qui est entre autre constituée d'un domaine de liaison à RB similaire à celui retrouvé chez E1A d'adénovirus. La première étape de ce travail de thèse a porté sur l'analyse de la protéine CLINK et plus particulièrement l'effet de cette protéine sur le cycle cellulaire, sur la transcription pol III en général et sur la transcription des SINE endogènes de plantes. La seconde partie de cette étude porte sur la fonction des éléments SINE de plantes au sein de la cellule. Chez les mammifères, l'élément SINE Alu est capable de jouer un rôle dans la physiologie de la cellule en réponse à certains stress. En effet, la transcription de ces éléments est activée à la suite d'une infection par certaines familles de virus. Les transcrits ainsi produits sont alors capables d'interagir avec la protéine PKR, une kinase d'eIF2α. Ainsi, les éléments SINE sont capables d'intervenir dans des processus clefs de la cellule comme le mécanisme de régulation de la traduction. La seule kinase d'eIF2α identifiée chez les plantes est la protéine GCN2. Ainsi, nous avons choisit de caractériser la fonction de cette protéine chez Arabidopsis. Nous avons déterminé les mécanismes de régulation de la protéine en mettant en évidence certains inducteurs spécifiques aux plantes. Ce travail a permis de montrer l'importance de la protéine pour la plante et de découvrir des fonctions potentielles de la protéine dans des voies de stress typiques des végétaux. Enfin, l'impact des SINE de plantes sur l'activité de GCN2 a été analysé.
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Romero, barrios Natali. "Non-codings RNAs, regulators of gene expression in Arabidopsis thaliana root developmental plasticity Noncoding Transcription by Alternative RNA Polymerases Dynamically Regulates an Auxin-Driven Chromatin Loop Battles and hijacks: noncoding transcription in plants Long noncoding RNA modulates alternative splicing regulators in Arabidopsis Detection of generic differential RNA processing events from RNA-seq data." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS128.
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Les techniques de séquençage à haut-débit développées ces dernières années ont permis d'identifier des milliers d’ARN non-codants et des événements tels que l’épissage ou l’édition. Cette approche est à l’origine d’une meilleure compréhension des mécanismes régulant l'expression des gènes. Les longs ARN non-codants (lncARN) ont ainsi émergé comme des acteurs clés de la régulation de divers processus développementaux. Ils agissent soit directement sous leur forme longue par des interactions lncARN-protéine(s) soit après une étape de maturation qui génère des siARN ou des miARN régulateurs, menant à l’extinction génique par clivage des ARNm, la répression de la traduction ou en entrainant des modifications épigénétiques (ADN/chromatine) de leurs cibles. L’objectif de cette thèse était d’élucider les mécanismes d'action de lncARNs dans le développement de la plante. J'ai contribué à l'analyse de l'action du lncARN APOLO dans la régulation de la topologie de la chromatine chez Arabidopsis thaliana. Ensuite, j’ai concentré mes efforts sur le lncARN ASCO (Alternative Splicing COmpetitor) qui interagit avec les protéines NSRs (Nuclear Speckles RNA-binding Proteins) et participent au patron d’épissage de certains gènes cibles. Lors d’un traitement par l’auxine, NSRb est induit alors qu’ASCO est réprimé dans les racines. Le même type de traitement, chez le double mutant nsra/b et les lignées surexprimant ASCO, entraine déficience partielle dans la formation des racines latérales. En utilisant un nouvel outil bio-informatique appelé "RNAprof", nous avons détecté 1885 ARN différentiellement maturés entre le mutant nsra/b et la lignée sauvage traités à l’auxine. Parmi ces gènes, nous avons identifié ARF19, un régulateur clé de la voie de signalisation de l’auxine au cours de l'initiation et le développement de la racine. J’ai démontré qu'ARF19 interagit directement avec les NSRs et qu’il est différentiellement polyadénylé dans le double mutant nsra/b, conduisant à une isoforme plus courte du transcrit ARF19. D’autre part, parmi les gènes dérégulés de manière transcriptionnelle chez le mutant des gènes impliqués dans la signalisation par l’éthylène ont été identifiés. J’ai ensuite montré que plusieurs de ces gènes sont aussi dérégulés dans les plantes mutantes arf19-1 et arf19-2 en réponse à l’auxine, soutenant un rôle d'ARF19 dans la réponse croisée entre l’auxine et l’éthylène. Le gène NSRb est induit par l'éthylène et l'inhibition de la synthèse d'éthylène par l'AVG complémente le phénotype de racine latérale du mutant nsra/b en réponse à l’auxine. De plus, l'AVG et la surexpression d’ASCO augmentent l'accumulation de l’isoforme courte d’ARF19. Cette étude met en avant la capacité du lncARN ASCO à moduler l’épissage par le détournement des NSRs et la capacité des ARN non-codants à moduler l’épissageIn the last years, high-throughput sequencing techniques have made possible to identify thousands of noncoding RNAs and a plethora of different mRNA processing events occurring in higher organisms. This led to a better understanding of different regulatory mechanisms controlling gene expression. Long noncoding RNAs (lncRNAs) are emerging as key players in the regulation of varied developmental processes. They can act directly in a long form by lncRNA-protein interactions or be processed into shorter small si/miRNAs, leading to mRNA cleavage, translational repression or epigenetic DNA/chromatin modification of their targets. In this study, we aim to understand the mechanism of action of lncRNAs in plant development. Initially, I contributed to the analysis of the action of the APOLO lncRNA in chromatin topology regulation. Then, I focused my work on the lncRNA ASCO (Alternative Splicing COmpetitor) that interacts with NSRs (Nuclear Speckles RNA-binding Proteins) to modulate the splicing pattern of NSR-regulated mRNA targets. Auxin treatment induces NSRb and represses ASCO expression in roots. The nsra/b double mutant and ASCO overexpressing lines treated with auxin are partially impaired in lateral root formation. Using a new bioinformatic tool called “RNAprof”, we detected 1885 differential RNA processing events genome-wide in auxin-treated nsra/b mutants compared to WT. Among them, we identified ARF19, a key regulator of auxin signaling in lateral root initiation and development. I demonstrated that ARF19 is directly bound by both NSRs and that in the nsra/b double mutant ARF19 is alternatively polyadenylated leading to a short transcript isoform. Furthermore, among the transcriptionally deregulated genes in the nsra/b mutant plants, I identified an important group related to ethylene response. I further showed that several of these genes are also deregulated in the arf19-1 and arf19-2 mutants plants in response to auxin, supporting a role of ARF19 in the auxin-ethylene crosstalk. NSRb is also induced by ethylene and the inhibition of ethylene synthesis by AVG rescues the nsra/b double mutant lateral root phenotype in response to auxin. Moreover, AVG and ASCO overexpression lead to increased accumulation of the ARF19 short isoform. Altogether, this study shed new light on the role of the lncRNA ASCO in the regulation of RNA processing by hijacking NSRs and the capacity of non-coding RNAs to modulate splicing
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Smith, Stephanie J. "Understanding genetic regulation of UV-B responses in Arabidopsis thaliana." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-1/r1/smiths/stephaniesmith.pdf.
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Bahirwani, Vishal. "Exploring transcription patterns and regulatory motifs in Arabidopsis thaliana." Thesis, Manhattan, Kan. : Kansas State University, 2010. http://hdl.handle.net/2097/4194.
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Kannangara, Rubini Maya. "Identification of transcription factor target genes in Arabidopsis thaliana." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444343.
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Izhaq, Farhaj. "Functional characterization of WIP transcription factors in Arabidopsis thaliana." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112063.
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Le déterminisme du sexe est un processus qui aboutit à la séparation physique des structures à l’origine des gamètes mâles et femelles, soit sur des fleurs séparées sur une même plante, pour les espèces monoïques, soit sur des individus séparés, dans le cas des espèces dioïques. Ce mécanisme favorise la fécondation croisée et augment ainsi la variabilité génétique. Il pourrait être influencé par les facteurs endogène (génétique ou hormonal) ou environnementaux. Chez le melon, le déterminisme du sexe est contrôlé par le gène A (andromonoecious) et le gène G (gynoecious). Le gène A code pour 1-aminocyclopropane-1-carboxylique acide synthase (ACS), un enzyme impliqué dans la voie de biosynthèse d’éthylène qui inhibe le développement des étamines dans les fleurs femelles. Le gène G code pour une protéine C2H2 à doigt de zinc appartenant à la famille WIP de facteurs de transcription qui inhibe le développement des capelles dans les fleurs mâles. Chez Arabidopsis thaliana, Il y a six gènes WIP et on en sait très peu sur leur fonction moléculaire. TT1/AtWIP1 est impliqué à l’accumulation de PA dans endothélium de graines. NTT/AtWIP2 est impliqué dans le développement de TRANSMITTING TRACT de carpelle. Dans cette thèse, nous avons essayé de mettre en évidence la fonction moléculaire de gènes WIP. Dans cette étude, nous avons montré que les gènes WIP des espèces différents partiellement restaurent le phénotype de graines jaune de tt1-3 mutants et régulent positivement les gènes tardifs de biosynthèse de flavonoïdes chez Arabidopsis thaliana La complémentation fonctionnelle de mutants tt1-3 par le gène WIP de melon et le gène WIP de la mousse montre que les gènes WIP ont la même fonction globale mais diffèrent à l’échelle spatio-temporelle. Il a été montré que le second motif conservé, à l’extrémité N-terminal, du gène TT1 était essentiel pour qu’il soit fonctionnel. La substitution d’acides aminés de ce motif (N2) par des alanines diminue l’accumulation de proanthocyanidines (PA) dans l’endothélium de la graine. TT1 perturbe également le développement des pétales, des étamines et des carpelles quand il est surexprimé de manière ectopique sous le contrôle des promoteurs d’AP3 et CRC. Il a été exprimé dans les racines secondaires sous le promoteur du gène SOLITARY ROOT (SLR/IAA14) ainsi que dans les stipules sous le promoteur du gène GLABROUS1 (GL1). TT1 inhibe le développement des racines secondaires et la formation des trichomes sur les feuilles. Dans cette étude, nous avons constaté que TT1 agit comme un inhibiteur de la formation d’organes quand il est exprimé de manière ectopique. On cherchera dans cette étude à comprendre les mécanismes mis en jeu lors de l’arrêt du développement de ces organes au cours du déterminisme du sexe et a évoqué de nouvelles pistes pour expliquer ce processusSex determination in plants is a process that results the development of either male or female flower on the same or different individuals. This mechanism enhances the cross pollination and raises the genetic variability. It can be influenced by endogenous (genetic or hormonal) and/or external environmental factors. In melon, gene A arrests the stamen development in the female flowers and gene G arrests the development of carpel in the male flowers hence these two genes control the sex determination mechanism in melon. Gene A encodes 1-aminocyclopropane-1-carboxylic acid synthase (ACS), an enzyme which is involved in the ethylene biosynthesis pathway. Gene G encodes a C2H2 zinc finger proteins that belongs to WIP family of transcription factors. In Arabidopsis thaliana, there are six WIP genes and very little is known about their molecular function. TT1/AtWIP1 is involved in the accumulation of PA in the seed endothelium. NTT/AtWIP2 is involved in the development of transmitting tract in the carpel. In this thesis, we tried to highlight the molecular function of the WIP genes. Here we show that WIP genes from different species partially restore the yellow seed coat color phenotype of tt1-3 mutant and upregulate the late flavonoid biosynthetic genes. The functional complementation of tt1-3 mutants by WIPs from Cucumis melo and Physcomitrella patens indicates that WIP genes have the same global function but differ on the spatio-temporal level. Second conserved motif in the N-terminus of TT1 protein was found to be essential for its proper function as alanine scanning of N2 motif of TT1 decreased the accumulation of PAs in the seed endothelium. TT1 disturbed the development of petals, stamens and carpels in flower when ectopically expressed under AP3 and CRC promoter. TT1 was expressed in the lateral roots under the promoter of SOLITARY ROOT (SLR/IAA14) and in the stipules under the promoter of GLABROUS1 (GL1). TT1 was able to inhibit the development of the lateral roots and leaf trichomes. In this study, we found that TT1 can act as organ inhibitor when ectopically expressed. Our study will help us to understand the organ arrest during sex determination mechanism and will evoke new dimensions for further explanations of this process
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Norris, Susan Renee 1969. "Genetic dissection of phytoene desaturation in Arabidopsis thaliana." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282388.
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Carotenoids are C₄₀ tetraterpenoids synthesized by nuclear-encoded, multi-enzyme complexes located in the plastids of higher plants. In order to further understand the components and mechanisms involved in carotenoid biosynthesis, our laboratory has identified Arabidopsis thaliana mutants that disrupt this pathway. Here, I report the identification and characterization of three non-allelic albino mutations, pds1, pds2, and pds3 (pds = b phytoene desaturation), that are disrupted in phytoene desaturation, an early step in carotenoid biosynthesis. pds1 and pds2 have been more thoroughly characterized than pds3. Surprisingly, neither pds1 nor pds2 maps to the locus encoding the phytoene desaturase enzyme, indicating the products of at least three loci are required for phytoene desaturation. Electron transport chain components are hypothesized to be involved in phytoene desaturation and the analysis of pds1 and pds2 provide the first genetic evidence that plastoquinone is an essential component in carotenoid biosynthesis. Both mutants are plastoquinone and tocopherol deficient, in addition to their inability to desaturate phytoene, affecting distinct steps of the common plastoquinone/tocopherol biosynthetic pathway. The pds1 mutation affects the enzyme p-hydroxyphenylpyruvate dioxygenase (HPPD) as it can be rescued by growth on the product but not the substrate of this enzyme, homogentisic acid and p-hydroxyphenylpyruvate, respectively. The pds2 mutation most likely affects the prenyl/phytyl transferase enzyme of this pathway. Additionally, I report the isolation of an Arabidopsis HPPD cDNA, the first from a higher plant, which encodes a 50 kD polypeptide with between 29 and 40% identity to non-plant HPPDs. Alignment of the Arabidopsis HPPD with non-plant HPPDs identifies 38 identical amino acid residues, including six tyrosine and histidine residues thought to form the ferric iron center of the enzyme. When expressed in E. coli, the Arabidopsis HPPD catalyzes the accumulation of two compounds, homogentisic acid and ochronotic pigment, a polymerized oxidation product of homogentisic acid. Additionally, the Arabidopsis HPPD locus and the pds1 locus co-segregate. Finally, and most-significantly, the constitutive expression of the Arabidopsis HPPD cDNA in the pds1 mutant background complements the pds1 mutant. Taken together, these data suggest that pds1 is a mutation in the HPPD gene.
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Smith, Lisa M. "Genetic analysis of RNA silencing in Arabidopsis thaliana." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435020.
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Collier, Sarah A. "Genetic analysis of Cajal bodies in Arabidopsis thaliana." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410501.
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Ahmed, Helal Uddin. "Mapping stress tolerance genetic loci in Arabidopsis thaliana." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246628.
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Ward, Sally P. "Genetic dissection of auxin signalling in Arabidopsis thaliana." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263773.
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Coles, Jeremy Paul. "Genetic manipulation of gibberellin biosynthesis in Arabidopsis thaliana." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263987.
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Stevenson, David Sinclair. "Genetic modifiers of transgene expression in Arabidopsis thaliana." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337084.
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Muttucumaru, Damayanthi Grace Niranjala. "Isolation and characterisation of a putative Arabidopsis thaliana transcription factor." Thesis, University of Hertfordshire, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275131.
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Weerathunga, Arachchilage Achira S. "A Novel Transcription Factor in Arabidopsis thaliana Abiotic Stress Response." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2114.
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Plants respond to environmental stress by altering their gene expression. Under stress conditions some genes are activated and some genes are repressed. Even though a lot of work has been done to understand mechanisms of gene activation under abiotic stress very little information is available on how stress responsive genes are kept repressed under normal growth conditions. Recent work has revealed that plants use transcriptional repression as common mechanism of gene repression. Transcriptional repression is achieved by recruitment co-repressor complexes to the target genes. Recent studies have revealed that the co-repressor LUH complexes with SLK1 and SLK2 to silence Arabidopsis thaliana stress responsive genes. However, the transcription factors involved in the recruitment of this complex to its target genes are not known. In this study, we identified SLK2INT1, as a novel transcription factor that is involved in silencing of select Arabidopsis thaliana stress responsive genes by recruiting the LUH-SLK2 complex.
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Velanis, Christos N. "Regulation of transcription by Ultraviolet-B radiation in Arabidopsis thaliana." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6204/.
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Plants are sessile photo-autotrophic organisms and need to adapt constantly to a dynamic environment. Light is of utmost importance for plants to be able to monitor their surroundings. Ultraviolet-B radiation (UV-B; 280-315 nm) is an intrinsic part of sunlight and, depending on the wavelength and the fluence rate, it may be a stressful signal or an “informational” one. The so called photomorphogenic responses of plants to UV-B are largely mediated by the UV-B specific photoreceptor UV RESISTANCE LOCUS 8 (UVR8), which “senses” UV-B via a tryptophan based mechanism. UVR8 is localised in the cytoplasm and the nucleus mainly as a homodimer. Upon UV-B irradiation it splits to its monomers and accumulates in the nucleus where it has been found to interact with the E3 Ubiquitin ligase COP1. In the nucleus UVR8 has been shown to associate with chromatin on loci of UV-B responsive genes, including that encoding for the bZIP transcription factor (TF) ELONGATED HYPOCOTYL 5 (HY5), a key effector of UVR8-dependent signalling pathways. The binding of UVR8 to chromatin appears to take place via interaction with histones (H2B in particular) rather than DNA itself. However, this association with chromatin seems not to be UV-B specific. The above data suggest a mechanistic basis for an assumed function of UVR8 in the regulation transcription. It seems likely that UVR8 interacts with other proteins associated with chromatin to promote remodelling and/or recruits/activates TFs which in turn stimulate transcription of its target genes. The main objective of this study was to address the above working hypothesis.
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Bielecka, Monika. "Analysis of transcription factors under sulphur deficiency stress." Phd thesis, kostenfrei, 2007. http://opus.kobv.de/ubp/volltexte/2007/1481/.
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Steynen, Quintin John, and University of Lethbridge Faculty of Arts and Science. "Genetic analysis of leaf vascular patterning in Arabidopsis thaliana." Thesis, Lethbridge : University of Lethbridge, University of Lethbridge. Faculty of Arts and Science, 2001, 2001. http://hdl.handle.net/10133/143.
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I have isolated and characterized a recessive mutation in the Forked (FKD) gene that results in the abnormal initiation of vascular bundles in the foliar organs, such that the apices of the vascular bundles initiate freely. Once initiated, the development of Fkd vascular bundles is like wild type, generating an open vascular pattern of similar complexity to the closed venation pattern of wild type. Despite the significant alteration in the vascular pattern, Fkd plants are morphologically indistinct from wild type. fkd mutants do not show altered sensitivity to the effects of auxin and show additive phenotypes with auxin response mutants, suggesting the FKD is part of a pathway acting independently of auxin. The similarity of the open vascular pattern of Fkd plants to that of ancestral vascular plants suggests that acquisition of this pathway may have been critical in the evolution of the closed vascular pattern.x, 55 leaves : ill. ; 28 cm.
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Bolbol, Ahmed A. E. "Genetic analysis of postzygotic hybridisation barriers in Arabidopsis thaliana." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537702.
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Most studies of plant hybridisation are concerned with documenting its occurrence in different plant groups. Many flowering plants are polyploids and seeds developed from crosses between individuals of different ploidies usually show abnormal features and often abort. The success or failure of interploidy crosses is very important to understanding the evolution of plants as well as to agriculture, but much remains to be learned about the nature of hybridisation barriers. Several mechanisms have been proposed to explain postzygotic barriers, including negative interactions between diverged sequences, global genome rearrangements, and widespread epigenetic reprogramming. Some recent advances in our understanding of the process of hybridisation are derived from different experimental studies on a series of A. thaliana ecotypes. Crosses between diploid (2x) and tetraploid (4x) individuals of the same ecotype can result in F1 lethality, and this dosage-sensitive incompatibility plays a major role in polyploidy speciation research. We have performed interploidy crosses between different diploid maternal A. thaliana ecotypes and tetraploid paternal Col-0 ecotype and identified a genetic variation in F1 lethality. We also found that maternal parents of some ecotypes such as Tsu-1 suppressed the F1 lethality caused by paternal-excess interploidy cross of Col-0 ecotype. A preliminary mapping exercise produced advanced backcross populations that are suitable for mapping maternal modifiers and for the identification of modifier genes. Furthermore, we studied the killer effect caused by Col-0 and identified three additive QTL that affect the rate of postzygotic lethality in F1 during interploidy crosses. This information will facilitate the identification of paternal genes that cause F1 lethality and contribute to reproductive isolation. The moa-1 (mosaic aneuploidy 1) mutant of A. thaliana was obtained in a screen of chemically (EMS) mutagenised seeds of Landsberg erecta (Ler). moa-1 has various phenotypic differences to wild type; the preliminary karyotype analysis showed that the cells of individual moa-1 mutant plants have a variable number of chromosomes (usually between 11-18). In contrast, the cells of wild type Arabidopsis plants and conventional aneuploids have a fixed number of chromosomes in each somatic cell. This data showed that all moa-1 plants have an abnormal number of chromosomes and thus they were termed as mosaic aneuploids.
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Diaz, Patrick Loyola. "Genetic strategies to manipulate meiotic recombination in Arabidopsis thaliana." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271685.
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During meiosis eukaryotes produce four haploid gametes from a single diploid parental cell. In meiotic S-phase homologous chromosomes, which were inherited from maternal and paternal parents, are replicated. Homologous chromosomes then pair and undergo reciprocal crossover, which generates new mosaics of maternal and paternal sequences. Meiosis also involves two rounds of chromosome segregation, meaning that only one copy of each chromosome is finally packaged into the resulting haploid gametes. In this work I sought to genetically engineer two elements of meiosis, in order to generate tools which may be useful for plant breeding. The first project sought to generate a second division restitution (SDR) population, where the second meiotic division is skipped. This is created by crossing an SDR mutant, omission of second division1, which produces diploid pollen due to a defective meiosis-II, to a haploid inducer line, whose chromosomes are lost from the zygote post-fertilisation. This was intended to give rise to diploid plants possessing chromosomes from just the SDR parent. Importantly, the SDR parent used was heterozygous, meaning that SDR progeny should show mostly homozygous chromosomes, but with regions of residual heterozygosity, determined by crossover locations. This project succeeded in creating a small number of plants with the predicted SDR genotype, although a range of aberrant genotypes were also observed. I present several hypotheses that could account for the observed progeny genotypes. In a second project I attempted to direct meiotic recombination using DNA double strand breaks targeted to specific sites. This project used a spo11-1 mutant, which is unable to produce the endogenous meiotic DNA DSBs that normally mature into crossovers. Instead, TALFokI nucleases (TALENs) were expressed from meiotic promoters in order to generate exogenous DSBs at sites determined by the DNA binding specificity of the TAL repeat domains. The project succeeded in transforming TALENs into spo11-1 mutants and confirming their expression. However, this was not sufficient to recover the spo11-1 mutant infertility or direct crossovers. Potential reasons for this non-complementation are discussed, as well as their implications for control of meiotic recombination in plant genomes.
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Cui, Hang. "Genetic dissection of nonhost disease resistance in Arabidopsis thaliana." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/13510.
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The Arabidopsis mutant eds1(enhanced disease susceptibility1), which is known to be defective in some aspects of R gene-mediated and basal disease resistance, is also compromised in nonhost disease resistance. A genetic modifier screen was carried out in order to identify further genes involved in nonhost resistance against Blumeria graminis f. sp tritici race Sav GH135 (Bgt1). Here, we report the isolation and characterization of two mutations, designated sed1 (suppressor of ed1) and sed2, both of which suppress eds1-mediated susceptibility towards Bgt1. The sed1eds1 mutant line exhibited restricted penetration of Bgt1 and a low formation frequency of haustoria and secondary hyphase. Loss of SED1 function also resulted in enhanced NHR against Bgt race W11S (Bgt2) and Blumeria graminis f. sp. hordei isolate 139 (Bgh) in an eds1 genetic background. However, sed1eds1 plants still maintained susceptibility against a broad-spectrum of host pathogens. Moreover, resistance against the nonhost bacterial pathogen Pseudomonas fluorescence was not affected, indicating that SED1is specifically required for establishment of NHR against powdery mildews. The sed2 mutant was initially isolated from a systemic acquired resistance (SAR) mutant screen using activated tagged populations of Arabidopsis and found to exhibit enhanced resistance to Hyaloperonospora parasitica Noco2. The sed2 mutant also suppressed eds1-mediated susceptibility towards Bgt1. The sed2eds1double mutant showed resistance against Bgt1 with regard to penetration and the formation of haustoria and secondary hyphae. Sed2eds1double mutants were also resistant to a series of host bacterial and oomycete pathogens. Thus, sed2 acts as a suppressor of eds1 establishing resistance against host and nonhost pathogens. This mutation mapped to a 400 kb interval between markers nga280 and T8L23 on chromosome I.
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Kühn, Kristina. "Analysis of components of the mitochondrial transcription machinery in Arabidopsis thaliana." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979811651.
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Edwards, D. B. "Isolation and characterisation of CCAAT box transcription factors from Arabidopsis thaliana." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598782.
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This project sets out to understand further the use of the conserved DNA sequence motif CCAAT in the modulation of plant gene transcription, by the isolation and characterisation of CCAAT box binding proteins (CBP's) from the model plant Arabidopsis. A highly conserved CBP complex consisting of CBP2, 3 and 5 has previously been identified in a range of organisms including yeast and vertebrates. Several strategies for the isolation of Arabidopsis CBP homologues were attempted. Functional complementation of the yeast HAP2 mutant identified three independent Arabidopsis CBP2 cDNAs. Searching the Arabidopsis expressed sequence tag (est) database revealed two forms each of CBP3 and CBP5. The presence of multiple forms of each CBP homologue is unusual as they are encoded by a single gene in yeast and vertebrates. These seven cDNAs were sequenced on both DNA strands and the putative protein sequence determined. Southern hybridisation gave an indication of the genomic copy number of each clone, while hybridisation of labelled cDNAs to RNA extracted from a range of tissues characterised their expression pattern. While CBP2 and CBP5 homologues were expressed equally in each tissue analysed, the two CBP3 cDNAs were preferentially expressed in aerial parts. Comparison of protein sequences with other CBPs identified conserved amino acid residues that have been shown to be of functional importance. These conserved domain sequences were also used to examine the evolutionary relationship of the multiple Arabidopsis forms and those from other organisms. The identification of multiple, novel forms of CBP from Arabidopsis is discussed in relation to their potential mode of action and role in plant development.
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Kühn, Kristina. "Analysis of components of the mitochondrial transcription machinery in Arabidopsis thaliana." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15453.
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In der vorliegenden Arbeit wurde die Transkription mitochondrialer Gene durch die kernkodierten Phagentyp-RNA-Polymerasen RpoTm und RpoTmp der Pflanze Arabidopsis untersucht. Im Mitochondriengenom von Arabidopsis wurden f r 12 Gene Promotoren bestimmt. Diese zeigten verschiedene Sequenzelemente und wichen meist von der f r Dikotyle publizierten Konsensussequenz ab. F r die Mehrheit der Gene wurden multiple Promotoren identifiziert. Es wurden weiterhin Promotoren nachgewiesen, welche die Transkription vermutlich nicht funktioneller Sequenzen aktivieren. Architektur, Lokalisation und Nutzung mitochondrialer Promotoren implizieren eine wenig stringente Kontrolle der Transkriptionsinitiation in Arabidopsis-Mitochondrien. Zur Analyse der Funktionen von RpoTm und RpoTmp wurde ein in vitro-Transkriptionssystem entwickelt. Da RpoT-Enzyme m”glicherweise Kofaktoren ben”tigen, wurde in Arabidopsis nach Genen potentieller mitochondrialer Transkriptionsfaktoren gesucht. Als mitochondriales Protein mit Žhnlichkeit zu mtTFB, einem essentiellen Transkriptionsfaktor in Hefemitochondrien, wurde MetA identifiziert. In in vitro-Assays initiierte RpoTm an verschiedenen Promotoren die Transkription, w„hrend RpoTmp keine signifikante Promotorspezifit„t zeigte. Die spezifische Promotornutzung durch RpoTm erforderte superhelikale DNA. Weder RpoTm noch RpoTmp wurde durch MetA stimuliert. Eine mtTFB-„hnliche Funktion von MetA ist daher unwahrscheinlich. F r MetA wurde ausserdem eine engere phylogenetische Beziehung zu nukle„ren rRNA-Dimethylasen als zu mtTFB ermittelt. Die hier vorgestellten Studien belegen die Transkription mitochondrialer Gene in Arabidopsis durch RpoTm; f r RpoTmp ist eine nicht-redundante Transkriptionsfunktion denkbar. Die Kofaktor-unabh„ngige Spezifit„t von RpoTm f r verschiedene Promotoren und die wenig stringente Initiationskontrolle in vivo legen nahe, dass eine individuelle Regulation mitochondrialer Gene in Arabidopsis auf Transkriptionsebene nicht erfolgt.Mitochondria depend on a nucleus-encoded transcription machinery to express their genome. The present study examined the transcription of mitochondrial genes by two nucleus-encoded phage-type RNA polymerases, RpoTm and RpoTmp, in the plant Arabidopsis. For selected mitochondrial genes in Arabidopsis, transcription initiation sites were determined. Most genes were found to possess multiple promoters. The identified promoters displayed diverse sequence elements and mostly deviated from a nonanucleotide consensus derived previously for dicot mitochondrial promoters. Several promoters were detected that activate transcription of presumably non-functional sequences. Promoter architecture, distribution and utilization suggest a non-stringent control of transcription initiation in Arabidopsis mitochondria. An in vitro transcription system was set up to elucidate the roles of RpoTm and RpoTmp. Since RpoT enzymes possibly require auxiliary factors, the Arabidopsis genome was screened for potential cofactors of phage-type RNA polymerases. A mitochondrial protein (MetA) with similarity to mtTFB, an essential transcription factor in yeast mitochondria, was identified. In in vitro transcription studies, RpoTm recognized various promoters whereas RpoTmp displayed no significant promoter specificity. Promoter recognition by RpoTm depended on supercoiled DNA templates. Transcription initiation by RpoTm or RpoTmp was not affected by MetA, indicating that MetA is not functionally equivalent to mtTFB. Besides, MetA was found to be more closely related to non-mitochondrial rRNA dimethylases than to mtTFB. The present study establishes RpoTm to transcribe mitochondrial genes; RpoTmp may have a non-overlapping transcriptional role in mitochondria. The cofactor-independent promoter specificity of RpoTm and the apparently non-stringent control of transcription initiation in vivo imply that mitochondrial genes in Arabidopsis may not be regulated individually at the transcriptional level.
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Czechowski, Tomasz. "Nitrogen signalling in Arabidopsis thaliana." Phd thesis, [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975976095.
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Coen, Olivier. "Developmental control of flavonoid biosynthesis in the seeds of Arabidopsis thaliana." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS584.
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Les graines d’Arabidopsis sont constituées de trois principaux compartiments : l’embryon, l’albumen et les tissus maternels. Ces derniers sont composés en particulier d’une enveloppe, impliquée dans la protection de la graine, sa dormance, ainsi que dans le transport de nutriments. L’endothélium est la couche cellulaire la plus interne de l’enveloppe, et tient lieu d’interface entre l’albumen et le reste de l’enveloppe. C’est aussi le site de production dans la graine des proanthocyanidines (PAs), un type particulier de flavonoïdes, d’intérêt à la fois physiologique et agronomique, et responsables de la couleur marron des graines d’Arabidopsis. À ce jour, une vingtaine de gènes impliqués dans l’accumulation de PAs ont été découverts et nommés TRANSPARENT TESTA (TT) ou TRANSPARENT TESTA GLABRA (TTG), en référence à la couleur jaune des graines mutantes correspondantes. Contrairement à d’autres gènes TT ou TTG, montrés être impliqués dans des processus enzymatiques ou de régulation transcriptionnelle, on suspecte que TT16, TT1 et TTG2 sont plutôt impliqués dans des mécanismes développementaux, ce que nous nous proposons d’étudier ici en détail. Dans cette étude, nous montrons que TT16 et TT1 contrôlent la morphologie et la différentiation des cellules de l’endothélium et de sa couche cellulaire adjacente, l’« ii1’ », tandis que TTG2 apparaît ne contrôler que la différentiation de l’endothélium. Nos résultats suggèrent aussi que TT16, TT1 and TTG2 contrôlent différents aspects du profil développemental de l’ii1’. Par ailleurs, nous étudions les mécanismes moléculaires impliqués dans la déposition d’une barrière de cutine apoplastique séparant albumen et endothélium. Nos résultats indiquent en particulier que cette déposition fait partie du processus de différentiation de l’endothélium et qu’elle est contrôlée par TT16, TT1, et dans une moindre mesure TTG2. Finalement, nos données indiquent que le développement et la différentiation de l’endothélium – incluant la déposition de cette barrière apoplastique - sont contrôlés par la fécondation de la cellule centrale du sac embryonnaire, tandis que le développement de l’ii1' requiert aussi la fécondation de la cellule-œufIn Arabidopsis, seeds are composed of three main compartments: an embryo, an endosperm and maternal tissues. The latter comprise in particular a seed coat, involved in seed protection, nutrient transport and dormancy. The endothelium is the innermost cell layer of the seed coat, acting as the interface between seed coat and endosperm. Moreover, the endothelium is the production site of proanthocyanidins (PAs), a class of flavonoid compounds of physiological and agricultural interest that give their brown color to Arabidopsis seeds. To date, several genes involved in PA accumulation in the endothelium have been discovered and named TRANSPARENT TESTA (TT) or TRANSPARENT TESTA GLABRA (TTG), according to the yellow color of their respective mutant seeds. Contrary to other TT and TTG genes, rather involved in enzymatic processes or transcriptional regulation, TT16, TT1 and TTG2 are thought to be involved in developmental processes, which we propose here to thoroughly characterize. In this study, we show that TT16 and TT1 control cell morphology and differentiation in the endothelium and in its adjacent cell layer, the so-called ii1’, whereas TTG2 appears to play roles in endothelium differentiation solely. Our results also suggest that TT16, TT1 and TTG2 control different aspects of the ii1’ developmental patterning. Furthermore, we shed light on genetic mechanisms controlling the deposition of an apoplastic cutin barrier separating endothelium and endosperm. In particular, our results indicate that such a deposition makes part of endothelium differentiation process and is controlled by TT16, TT1, and in a lesser extent TTG2. Finally, our data indicate that endothelium development and differentiation – including deposition of this apoplastic barrier - are controlled by the fertilization of the embryo sac central cell, whereas ii1’ development also requires the fertilization of the egg-cell
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Lawrence, Emma Jane. "Identifying natural modifiers of meiotic crossover frequency in Arabidopsis thaliana." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289733.
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During meiosis, homologous chromosomes pair and undergo reciprocal genetic exchange, producing crossovers. This generates genetic diversity and is required for balanced homolog segregation. Despite the critical functions of crossovers, their frequency and distribution varies extensively within and between species. This crossover variation can be caused by trans-modifiers within populations, which encode diffusible molecules that influence crossover formation elsewhere in the genome. This project utilised natural accessions of Arabidopsis thaliana to identify trans-modifying loci underlying crossover variation within the species. I performed Quantitative Trait Loci (QTL) mapping using a fluorescence-based crossover reporter system to measure recombination frequency in a genomic interval on chromosome 3, termed 420. Mapping in a Col-420 × Bur-0 F2 population revealed four major recombination QTLs (rQTLs) that influence crossover frequency. A novel recessive rQTL on chromosome 1 that reduced crossovers within the interval was fine-mapped to a premature stop codon in TATA Binding Protein (TBP)-associated factor 4b (TAF4b) in Bur-0 (taf4b-1). TAF4b is a subunit of the TFIID complex, a multi-protein general transcription factor complex comprising TBP and numerous TAFs that forms a component of the pre-initiation complex that recruits RNA polymerase II to promoters. Transformation-based complementation experiments and the isolation of several independent taf4b alleles provided genetic proof that TAF4b is essential for wild-type levels of crossover within 420. Analysis of the prevalence of the taf4b-1 mutation in the global Arabidopsis accession collection demonstrated its specificity to three accessions in the British Isles. A combination of cytology, genetic analysis using additional fluorescent reporter lines, and sequencing in F2 recombinant populations demonstrated a genome-wide reduction in crossover frequency in taf4b-1. In addition, RNA sequencing identified numerous transcriptional changes in taf4b-1. Both up- and down-regulated gene sets displayed significant enrichment for genes that are predominantly expressed in meiocytes, and several gene ontology terms pertaining to protein modification and meiotic processes. These results further demonstrate the existence of genetic modifiers of crossover frequency in natural populations of A. thaliana, and the characterisation of a novel trans-modifier of recombination, TAF4b. This signifies a novel function for TAF4b in Arabidopsis, and further enhances our understanding of the molecular factors controlling the frequency and distribution of meiotic crossovers in plants.
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Cavel, Émilie. "Caractérisation fonctionnelle de deux gènes nucléaires codant des variants du facteur général de transcription TFIIB chez Arabidopsis thaliana." Perpignan, 2009. http://www.theses.fr/2009PERP0878.
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Chez les Eucaryotes, l’expression des gènes nucléaires est effectuée par trois ARN polymérases (ARNP) conservées qui, grâce aux Facteurs Généraux de la Transcription (GTF), peuvent reconnaître spécifiquement un promoteur et réaliser l’initiation de la transcription. Parmi ces facteurs, TBP et le facteur général de type B ont été conservés au cours de l’évolution et jouent un rôle central dans l’assemblage du complexe de préinitiation de la transcription. Bien que l’on pensait que les GTF étaient ubiquitaires, il est maintenant bien décrit que des variants des facteurs TBP et de type B sont apparus chez les animaux et qu’ils participent à des processus de régulation génique spécifiques. Cependant, chez les plantes, à l’exception du variant de TFIIB nommé pBrp1 (plant-specific TFIIB-related protein 1), il existe peu d’informations concernant l’existence de variants des GTF. Dans ce travail, nous rapportons l’identification de deux gènes chez Arabidopsis codant des variants de TFIIB, référencés comme pBRP2 et pBRP3. PBRP2 et pBRP3 présentent une distribution phylogénétique restreinte puisqu’ils ne sont détectés à ce jour uniquement dans la famille des Brassicacae, suggérant une émergence récente de ces gènes. De plus, pBRP2 et pBRP3 sont spécifiquement exprimés dans les organes reproducteurs de la plante et dans les graines sèches. Par le biais de la génétique inverse, nous avons démontré que pBrp2 est impliqué dans la prolifération de l’albumen et des gènes candidats, qui semblent être régulés par pBrp2, ont également été identifiés. Enfin, nous avons mis en évidence que pBrp3 semble intervenir au cours des stades tardifs de maturation de la graineIn eukaryotes, nuclear gene expression is accomplished by three conserved RNA polymerases (RNAP) which, through General Transcription Factors (GTFs), are capable of selective promoter recognition and achieve transcription initiation. Among those factors, TBP and the general transcription factor B have been evolutionary conserved and play a central role in preinitiation complex assembly. Although the GTFs have been thought to be ubiquitous, it is now well documented that animals have evolved variants of TBP and B-type factors to participate in specific gene regulation process. However in plants, with the exception of the TFIIB-variant called pBrp1 (plant-specific TFIIB-related protein 1), there is so far little information regarding the existence of GTF variants. In the present work, we report the identification of two Arabidopsis genes coding for TFIIB variants, referred to as pBRP2 and pBRP3. PBRP2 and pBRP3 present a restricted phylogenetic distribution, being detected to date only in the Brassicacae family, suggesting a recent emergence of these genes. Moreover, pBRP2 and pBRP3 are specifically expressed in the reproductive organs of the plant and in dry seeds. Using a reverse genetic approach, we have demonstrated that pBrp2 is involved in endosperm proliferation and candidate genes that seem to be regulated by pBrp2 have also been identified. Finally, we have highlighted that pBrp3 seems to be implicated during late stages of seed maturation
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Wiedemeier, Allison Merritt Dennings. "Analysis of Arabidopsis thaliana growth anisotropy mutants : genetic, physiological, and cytological characterization /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901300.
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Maurer, Alberto. "Molecular and genetic studies of iron homeostasis in Arabidopsis." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4476.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 18, 2008) Vita. Includes bibliographical references.
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Bonardi, Vera. "Molecular-genetic characterization of thylakoid protein phosphorylation in Arabidopsis thaliana." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-58763.
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Deyholos, Michael K. "Genetic regulation of vascular and floral patterning in Arabidopsis thaliana." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36911.
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The mechanisms that genes use to direct patterns of development are of fundamental interest. Using Arabidopsis thaliana as a model, I have investigated aspects of these mechanisms in the separate processes of vascular and floral development. Specifically, I conducted a screen for vascular-defective mutants, and analyzed a region of the genome that regulates the expression of the floral homeotic gene, AGAMOUS ( AG).In this report, I describe the identification of over forty mutants that are abnormal in tracheary element development or vein patterning. The spectrum of mutant phenotypes that I observed indicates that the mechanisms that pattern primary and secondary veins of leaves or cotyledons are at least partially separable; that among the genes that affect vascular development, a significant proportion are repressors of vascular differentiation; and that the majority of vascular mutants that can be identified in this type of screen have pleiotropic phenotypes.
I characterized two of the mutants, varicose ( vcs) and scarface (sfc), in more detail. vcs mutants are temperature sensitive, and at the non-permissive temperature, accumulate distended tracheary elements around veins. VCS is also required at an early stage of leaf development for normal vein patterning, and interacts with the AUXIN RESISTANT 1 gene in this process. sfc mutants fail to develop normal, contiguous vein networks in cotyledons, leaves, sepals, and petals. It is specifically the secondary and higher order veins in these organs that are affected by the mutation. sfc mutants have exaggerated responses to exogenous auxin, and the SFC gene overlaps in primary and secondary vein patterning functions with an auxin-response factor gene MONOPTEROUS.
This report also includes an analysis of the cis-regulatory regions that control expression of AGAMOUS, a gene that when properly expressed in two central domains of the developing flower, directs the formation of carpels and stamens. My dissection of an AG intragenic region demonstrated that AG expression in stamens can be activated independently of carpels. Moreover, the stamen-specific expression pattern was found to be independent of APETALA2, a known negative regulator of AG, while the carpel-specific expression pattern was shown to be independent of LEUNIG, another negative regulator of AG.
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Breen, Gordon James Leslie. "The genetic network directing root hair development in Arabidopsis thaliana." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520184.
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Hunter, B. C. "Genetic modifiers of hairpin-induced gene silencing in Arabidopsis thaliana." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604807.
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The Chalcone Synthase (CHS) gene codes for the first step of biosynthesis of the purple pigment anthocyanin. In this study, transgenic Arabidopsis plants with a hairpin construct homologous to part of the CHS coding sequence were used in a genetic screen to identify modifiers of hairpin silencing. Some putative genetic modifiers were identified, but these appear to be the result of transgene:transgene interaction based on shared promoter homology rather than being due to second site suppressors in the Arabidopsis genome. New transgenic Arabidopsis lines were made with hairpin constructs directed to either the promoter or the reading frame of the CHS gene and both types of transgenic showed an anthocyanin-deficient phenotype. For each construct a representative single-insert homozygous transgenic line was selected for subsequent work. Both transgenic lines showed increased methylation of their respective target site and contained short interfering RNA (siRNA) homologous to their target site. A collection of 59 putative modifiers of CHS silencing were tested with both transgenic lines using segregation analysis of the anthocyanin-deficient phenotype in the F2 generation of appropriate crosses. Mutants in AGO4, AGO6, DRD1, DRM2, NRPD2a and NRPE1 act as recessive second site modifiers of the CHS promoter hairpin line phenotype. These mutants are associated with a decrease in DNA methylation at the hairpin target site. Mutant alleles of the DCL4 and HEN1 genes reduce silencing of the CHS coding sequence hairpin. The reduction in silencing is greater in mutants that are hemizygous for the hairpin construct than in those that are homozygous for it. The increase in siRNA in the construct homozygotes, compared to that in the hemizygotes, is perhaps sufficient to overcome any modification of the phenotype by mutants of DCL4 and HEN1.
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Cano, Delgado Ana Isabel. "Genetic and molecular analysis of xylem development in Arabidopsis thaliana." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365009.
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Plant cell walls play a central role in cell growth and morphogenesis. All plant cells have a primary wall. The formation of a secondary cell wall is restricted to particular cell types, such as the xylem cells, highly lignified cells that provide support and transport functions to the plant. The mechanisms regulating secondary cell wall biogenesis remain largely unknown. To identify genes involved in such mechanisms, a genetic screen for mutants with altered xylem development in the primary root of Arabidopsis thaliana has been conducted. Three different classes of mutants were identified. They are characterised by increased number of xylem strands (m"), altered timing of protoxylem differentiation (tpx) and ectopic lignification (eh). Initial characterisation of the mutant phenotypes, establishment of different complementation groups and their map position in the Arabidopsis genome has been determined. Mutations in the EL [I locus have been characterised in further detail. The eli l mutants exhibited ectopic lignification of cells throughout the plant that never normally lignify. Xylem cells in elil were misshapen and failed to differentiate into continuous strands, causing a disorganised xylem. elil mutants also exhibited altered cell expansion resulting in a stunted phenotype. Abnormal distribution of cellulose and lignin was observed in elil cell walls. Ultrastructural analysis of elil cell walls using an anti-lignin antibody has revealed that that the ectopic deposition of lignin-like compounds occurs within an altered secondary wall. Furthermore, other previously described cell expansion mutants, such as lit, rswl (at the conditional temperature) and det3, exhibited lignification patterns reminiscent to that of elil mutants. Analysis of the genetic interactions of elil with the lit mutant revealed that ELlI and LIT genes act in independent pathways to control cell expansion. These results, together with the double mutant analysis of eli l with other cell expansion mutants suggested a link between cell growth and differentiation of secondary thickened walls. Map-based cloning placed the ELJ1 gene in a 140-Kb interval on the top arm of Arabidopsis chromosome V. A candidate gene approach was used that identified a gene encoding a cellulose synthase catalytic subunit (CesA), AthCesA-3 as a candidate. Sequence analysis revealed that the AthCesA-3 gene is mutated in two elil alleles sequenced, both mutations leading to amino acid substitutions. Initial complementation experiments of elil plants with the wild type AthCesA-3 gene appeared to restore the wild type phenotype, suggesting that mutations in the AthCesA-3 gene gave rise to the elil phenotypes. These studies represent an important contribution to our understanding of the molecular mechanism of cellulose deposition during cell expansion and secondary cell wall deposition during plant morphogenesis.
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Quiroz, Hugo Alejandro Campos-de. "Genetic analysis of the aliphatic glucosinolate pathway in Arabidopsis thaliana." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267260.
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King, Kathryn Elizabeth. "Genetic and molecular investigation of gibberellin signalling in Arabidopsis thaliana." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302206.
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Sarjeant, Adrian B. "The molecular genetic characterisation of the Arabidopsis thaliana LAX1 gene." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343147.
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Klejnot, John Timothy. "Molecular genetic studies of cryptochrome 2 function in Arabidopsis thaliana." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1666130271&sid=3&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Niyogi, Krishna K. (Krishna Kumar). "Molecular and genetic analysis of anthranilate synthase in Arabidopsis thaliana." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12668.
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