Relevant bibliographies by topics / Mating type locus

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Academic literature on the topic 'Mating type locus'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Mating type locus"

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Staben, Chuck. "The mating-type locus ofNeurospora crassa." Journal of Genetics 75, no. 3 (December 1996): 341–50. http://dx.doi.org/10.1007/bf02966313.

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Foulongne-Oriol, Marie, Ozgur Taskent, Ursula Kües, Anton S. M. Sonnenberg, Arend F. van Peer, and Tatiana Giraud. "Mating-Type Locus Organization and Mating-Type Chromosome Differentiation in the Bipolar Edible Button Mushroom Agaricus bisporus." Genes 12, no. 7 (July 16, 2021): 1079. http://dx.doi.org/10.3390/genes12071079.

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In heterothallic basidiomycete fungi, sexual compatibility is restricted by mating types, typically controlled by two loci: PR, encoding pheromone precursors and pheromone receptors, and HD, encoding two types of homeodomain transcription factors. We analysed the single mating-type locus of the commercial button mushroom variety, Agaricus bisporus var. bisporus, and of the related variety burnettii. We identified the location of the mating-type locus using genetic map and genome information, corresponding to the HD locus, the PR locus having lost its mating-type role. We found the mip1 and β-fg genes flanking the HD genes as in several Agaricomycetes, two copies of the β-fg gene, an additional HD2 copy in the reference genome of A. bisporus var. bisporus and an additional HD1 copy in the reference genome of A. bisporus var. burnettii. We detected a 140 kb-long inversion between mating types in an A. bisporus var. burnettii heterokaryon, trapping the HD genes, the mip1 gene and fragments of additional genes. The two varieties had islands of transposable elements at the mating-type locus, spanning 35 kb in the A. bisporus var. burnettii reference genome. Linkage analyses showed a region with low recombination in the mating-type locus region in the A. bisporus var. burnettii variety. We found high differentiation between β-fg alleles in both varieties, indicating an ancient event of recombination suppression, followed more recently by a suppression of recombination at the mip1 gene through the inversion in A. bisporus var. burnettii and a suppression of recombination across whole chromosomes in A. bisporus var. bisporus, constituting stepwise recombination suppression as in many other mating-type chromosomes and sex chromosomes.
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Judelson, H. S., L. J. Spielman, and R. C. Shattock. "Genetic mapping and non-Mendelian segregation of mating type loci in the oomycete, Phytophthora infestans." Genetics 141, no. 2 (October 1, 1995): 503–12. http://dx.doi.org/10.1093/genetics/141.2.503.

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Abstract DNA markers linked to the determinants of mating type in the oomycete, Phytophthora infestans, were identified and used to address the genetic basis of heterothallism in the normally diploid fungus. Thirteen loci linked to the A1 and A2 mating types were initially identified by bulked segregant analysis using random amplified polymorphic DNA markers (RAPDs) and subsequently scored in three crosses polymorphisms (SSCP), cleaved amplified polymorphisms (CAPS), or allele-specific polymerase chain reaction markers (AS-PCR). All DNA markers mapped to a single region, consistent with a single locus determining both mating types. Long-range restriction mapping also demonstrated the linkage of the markers to one region and delimited the mating type locus to a 100-kb region. The interval containing the mating type locus displayed non-Mendelian segregation as only two of the four expected genotypes were detected in progeny. This is consistent with a system of balance lethal loci near the mating type locus. A model for mating type determination is presented in which the balanced lethals exclude form progeny those with potentially conflicting combinations of mating type alleles, such as those simultaneously expressing A1 and A2 functions.
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Kanamori, Masaki, Hana Kato, Nobuko Yasuda, Shinzo Koizumi, Tobin L. Peever, Takashi Kamakura, Tohru Teraoka, and Tsutomu Arie. "Novel mating type-dependent transcripts at the mating type locus in Magnaporthe oryzae." Gene 403, no. 1-2 (November 2007): 6–17. http://dx.doi.org/10.1016/j.gene.2007.06.015.

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Judelson, Howard S. "Genetic and Physical Variability at the Mating Type Locus of the Oomycete, Phytophthora infestans." Genetics 144, no. 3 (November 1, 1996): 1005–13. http://dx.doi.org/10.1093/genetics/144.3.1005.

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Abstract Mating type in the oomyceteous fungus, Phytophthora infestans, is determined by a single locus. In a previous study of a few isolates, the locus segregated in a manner genetically consistent with its linkage to a system of balanced lethal loci. To determine the prevalence of this phenomenon within P. infestans, genetic analyses were performed using isolates representative of the diversity within the species that had been selected by DNA fingerprinting using probes linked to mating type. Non-Mendelian segregation of the mating type locus was observed in crosses performed with each isolate. An unusual group of isolates was identified in which the mating type determinants had been rearranged within the genome; these strains also produced an aberrantly large number of self-fertile progeny. Curiously, in all isolates, markers linked to the mating type locus appeared prone to duplication, transposition, deletion, or other rearrangement. This was not observed for loci unlinked to mating type. Data from the crosses and analyses of marker variation were used to erect models to explain the bases of mating type determination and of the unusual segregation of the chromosomal region containing the mating type locus.
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Lengeler, Klaus B., Deborah S. Fox, James A. Fraser, Andria Allen, Keri Forrester, Fred S. Dietrich, and Joseph Heitman. "Mating-Type Locus of Cryptococcus neoformans: a Step in the Evolution of Sex Chromosomes." Eukaryotic Cell 1, no. 5 (October 2002): 704–18. http://dx.doi.org/10.1128/ec.1.5.704-718.2002.

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ABSTRACT The sexual development and virulence of the fungal pathogen Cryptococcus neoformans is controlled by a bipolar mating system determined by a single locus that exists in two alleles, α and a. The α and a mating-type alleles from two divergent varieties were cloned and sequenced. The C. neoformans mating-type locus is unique, spans >100 kb, and contains more than 20 genes. MAT-encoded products include homologs of regulators of sexual development in other fungi, pheromone and pheromone receptors, divergent components of a MAP kinase cascade, and other proteins with no obvious function in mating. The α and a alleles of the mating-type locus have extensively rearranged during evolution and strain divergence but are stable during genetic crosses and in the population. The C. neoformans mating-type locus is strikingly different from the other known fungal mating-type loci, sharing features with the self-incompatibility systems and sex chromosomes of algae, plants, and animals. Our study establishes a new paradigm for mating-type loci in fungi with implications for the evolution of cell identity and self/nonself recognition.
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LUDWIG, Lars R., Tina C. SUMMERFIELD, Janice M. LORD, and Garima SINGH. "Characterization of the mating-type locus (MAT) reveals a heterothallic mating system inKnightiella splachnirima." Lichenologist 49, no. 4 (July 2017): 373–85. http://dx.doi.org/10.1017/s0024282917000214.

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AbstractIn the present study, we characterized the mating-type locus ofKnightiella splachnirima(Icmadophilaceae) using degenerate and inverse PCR techniques. We screened for the presence of both mating-type locus idiomorphs in DNA extracts of minuscule samples of haploid thalline tissue. We found that only one of the two idiomorphs was present in each sample, and the mating-type ratio (MAT1-1:MAT1-2) was very balanced, being 8:10 and 13:14 at local and global scales, respectively. This indicates that the species is probably self-incompatible and requires the presence of compatible mating partners for sexual reproduction (heterothallic mating system). Furthermore, we provide a mating-type screening protocol withK. splachnirimaspecific mating-type locus primers, which could serve as an essential tool for the conservation management of this rare Australasian endemic.
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Bubnick, Meggan, and A. George Smulian. "The MAT1 Locus of Histoplasma capsulatum Is Responsive in a Mating Type-Specific Manner." Eukaryotic Cell 6, no. 4 (February 23, 2007): 616–21. http://dx.doi.org/10.1128/ec.00020-07.

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ABSTRACT Recombination events associated with sexual replication in pathogens may generate new strains with altered virulence. Histoplasma capsulatum is a mating-competent, pathogenic fungus with two described phenotypic mating types, + and −. The mating (MAT) locus of H. capsulatum was identified to facilitate molecular studies of mating in this organism. Through syntenic analysis of the H. capsulatum genomic sequence databases, a MAT1-1 idiomorph region was identified in H. capsulatum strains G217B and WU24, and a MAT1-2 idiomorph region was identified in the strain G186AR. A mating type-specific PCR assay was developed, and two clinical isolates of opposite genotypic mating type, UH1 and VA1, were identified. A known − mating type strain, T-3-1 (ATCC 22635), was demonstrated to be of MAT1-2 genotypic mating type. The clinical isolates UH1 and VA1 were found to be mating compatible and also displayed mating-type-dependent regulation of the MAT transcription factors in response to extracts predicted to contain mating pheromones. These studies support a role for the identified MAT1 locus in determining mating type in H. capsulatum.
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Zambino, Paul, James V. Groth, Lewis Lukens, James R. Garton, and Georgiana May. "Variation at the b Mating Type Locus of Ustilago maydis." Phytopathology® 87, no. 12 (December 1997): 1233–39. http://dx.doi.org/10.1094/phyto.1997.87.12.1233.

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Population level diversity at the Ustilago maydis b mating type locus was determined in samples from four Minnesota locations using a combination of plate mating techniques and a polymerase chain reaction (PCR)-based assay. The PCR method allows rapid identification of b types from samples of natural populations and utilizes the hypervariable regions of the b locus that determine mating type specificity. Results demonstrated high levels of b diversity within populations, with one population yielding 17 of the total 18 b types found in the study. Pairwise GST values were in the range of 0.02 to 0.05, and common b mating types were found across broad geographic distances. These data demonstrated that very low levels of differentiation among U. maydis populations occur with respect to b locus variation. Consistent with frequency-dependent selection models, b types were represented at approximately equal frequencies within the entire Minnesota population. However, neutral evolutionary models for patterns of geographic distribution and variation at b cannot be entirely excluded. The importance to agricultural practices of understanding population genetic processes is discussed.
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Chaleff, D. T., and K. Tatchell. "Molecular cloning and characterization of the STE7 and STE11 genes of Saccharomyces cerevisiae." Molecular and Cellular Biology 5, no. 8 (August 1985): 1878–86. http://dx.doi.org/10.1128/mcb.5.8.1878.

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In the yeast Saccharomyces cerevisiae, haploid cells occur in one of the two cell types, a or alpha. The allele present at the mating type (MAT) locus plays a prominent role in the control of cell type expression. An important consequence of the elaboration of cell type is the ability of cells of one mating type to conjugate with cells of the opposite mating type, resulting in yet a third cell type, an a/alpha diploid. Numerous genes that are involved in the expression of cell type and the conjugation process have been identified by standard genetic techniques. Molecular analysis has shown that expression of several of these genes is subject to control on the transcriptional level by the MAT locus. Two genes, STE7 and STE11, are required for mating in both haploid cell types; ste7 and ste11 mutants are sterile. We report here the molecular cloning of STE7 and STE11 genes and show that expression of these genes is not regulated transcriptionally by the MAT locus. We also have genetically mapped the STE11 gene to chromosome XII, 40 centimorgans from ura4.
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Dissertations / Theses on the topic "Mating type locus"

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Henry, Julie Leanna. "Mating-type Locus Characterization and Variation in Pyrenophora semeniperda." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5948.

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Pyrenophora semeniperda is a generalist fungal pathogen that occurs primarily on monocot seed hosts. It is in the phylum Ascomycota, which includes both self-compatible (homothallic) and self-incompatible (heterothallic) species. Homothallic fungal species contain complementary mating-type (MAT) idiomorphs in a single unikaryotic strain, while heterothallic strains contain a single MAT idiomorph requiring interaction between strains of complementary mating-types for sexual reproduction to occur. Because the majority of P. semeniperda strains contained either MAT1 or MAT2, this species was provisionally categorized as heterothallic. However, many strains contain both MAT idiomorphs and appear to be homothallic. These results warranted a closer look at the MAT idiomorphs and the structure of the P. semeniperda genome in order to assure accurate characterization of the MAT locus. Additionally, an assessment of the geographic distribution of MAT idiomorphs provides us with insight into the genetic diversity of P. semeniperda and the reproductive strategies that it employs. In this study, we characterized the P. semeniperda MAT locus and assessed the idiomorph distribution of 514 isolates from 25 P. semeniperda populations collected from infected Bromus tectorum (cheatgrass) seeds. Additionally, we used simple sequence repeat (SSR) and MAT idiomorph length polymorphisms to demonstrate the existence of dikaryotic strains and pseudohomothallism in this fungus. We identified a unique variable number tandem repeat (VNTR) within each idiomorph of the MAT locus of P. semeniperda. Presence of the VNTR in all MAT loci analyzed from strains collected in the Intermountain West suggests ancient proliferation of this repeat. The persistence and effectiveness of P. semeniperda strains in the cheatgrass pathosystem depend not only on the density of the fungus in the soil, but also on the genetic heterogeneity of each population. Our study suggests that P. semeniperda genetic diversity is increased both through MAT locus-dependent sexual reproduction and asexually through anastomosis.
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Yee, Arthur Raymond. "Specificity at the b mating type locus of Ustilago maydis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ27270.pdf.

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Pardo, Eneida Hamam. "Organisation of the A mating type locus of Coprinus cinereus." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297260.

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O'Shea, Suzanne Frances. "Isolation and characterization of the B mating type locus of Coprinus cinereus." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320583.

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Olesnicky, Natalie Sonia. "Pheromones and receptors of the B mating type locus of Coprinus cinereus." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301396.

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Halsall, John Richard. "Isolation and characterisation of the B42 mating type locus of Coprinus cinereus." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:d5340e8b-29d7-4418-be27-f0c06e10ca18.

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C. cinereus, any two of which are sufficient to promote B-regulated development following cell fusion. The isolation of the B42 locus is described along with the DNA sequence analysis that identified nine B mating type genes within a 27kb B42 -specific DNA sequence. Six of the genes, with small transcripts of 800-900nt, encode the mating pheromone precursors and the other three, with 1.9 to 2-5kb transcripts, encode the transmembrane pheromone receptors. The genes are arranged in three groups, designated group 1, 2 and 3, each consisting of one receptor gene and two pheromone genes. B42 and B6 share the same alleles of the group 1 genes, but not those of groups 2 and 3. This was demonstrated by DNAsequence analysis and Southern blot analysis. None of the group 1 genes from B42 were able to activate B -regulated development in a B6 host when introduced by transformation but with one exception, all genes from group 2 and group 3 were able to do so. This analysis led to the recognition that the three genes in any one group are held together in an allele-specific DNA sequence and that Southern blot analysis and transformation can be used to identify shared alleles in uncloned loci. Extensive Southern analyses using cloned genes to probe genomic DNAs from strains having other B mating specificites showed that different B loci may share identical alleles of two groups of genes. Mating partners thus require different alleles of only one group of genes to generate a compatible B mating interaction. Transformation analyses with the same cloned genes confirmed the conclusions derived from the hybridisation data. Multiple B mating specificities thus appear to be derived from three groups of multiallelic and functionally redundant genes. A tenth gene located within the B42- specific DNA sequence encodes a putative transporter protein belonging to the major facilitator superfamily (MFS). In other genomic backgrounds this gene lies in homologous flanking sequences and its presence within the B42 locus is unlikely to be related to mating type function.
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Mathieu, Stephanie. "The Genetics of Arbuscular Mycorrhizal Fungi." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42770.

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Sexual reproduction is an important process amongst eukaryotic organisms, with one function being to maintain genetic variation. The idea that complex eukaryotic species can persist for millions of years in the absence of sex defies fundamental evolutionary dogma, yet a group of organisms known as ancient asexuals were thought to have evolved clonally under deep evolutionary time. Prominent among these are the arbuscular mycorrhizal fungi (AMF), which are obligate plant symbionts that colonize the root cells of plants and extend their hyphae into the soil assisting the plant in acquiring key nutrients. Unlike most eukaryotes, AMF cells are multinucleate with thousands of nuclei moving through a continuous cytoplasm. Genomic analyses have identified a putative mating-type (MAT) locus within the nuclear genomes of model AMF Rhizophagus irregularis, a region that in other fungi dictates the process of sexual reproduction. Additional findings demonstrated that AMF strains carry one of two nuclear organizations. They can be either homokaryotic (AMF homokaryons), where all nuclei within the cytoplasm are virtually identical, or heterokaryotic (AMF dikaryons), where two MAT-locus variants co-exist within the cytoplasm. Despite a lack of observable traits indicative of sex, this homo/heterokaryotic dichotomy is reminiscent of the nuclear organization of sexual fungi. My research aims to build on these findings to investigate the actual role of the MAT-locus in driving AMF reproduction. To address this, I build my thesis into three main chapters. The first chapter reviews our current understanding of AMF genetics and what drives genome evolution in these organisms. The second chapter establishes a relatively easy, inexpensive, and reproducible approach to genotype known MAT variants of R. irregularis in natural and experimental conditions. The last chapter uses experimental crossings between strains to assess cytoplasmic compatibility and nuclear exchange. I demonstrate that dikaryotic spore progenies can be formed after co-culturing two distinct AMF homokaryotic strains. Further analyses of various genomic regions also reveal possible recombination in homokaryotic spore progenies from co-cultures. Overall, this research provides new experimental insights into the origin of genetic diversity in AMF. These findings open avenues to produce genetically new AMF strains in the lab using conventional crossing procedures and provide a glimpse of the mechanisms that generate AMF genetic diversity in the field.
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Maroc, Laetitia. "Etude sur le changement de type sexuel et les cassures chromosomiques chez Candida glabrata A single Ho-induced doublestrand break at the MAT locus is lethal in Candida glabrata A new inducible CRISPR-Cas9 system useful for genome editing and study of double-strand break repair in Candida glabrata." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASL008.

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Le changement de type sexuel est une des stratégies développées par les champignons afin de favoriser la reproduction sexuée. Ce mécanisme permet à une cellule haploïde de donner naissance à une cellule de type sexuel opposé de façon qu’elles puissent se féconder. Cela a particulièrement été bien étudié chez la levure sexuée Saccharomyces cerevisiae mais la raison pour laquelle les éléments du changement de type sexuel ont été conservés dans des espèces comme Candida glabrata chez qui ni reproduction sexuée, ni changement de type sexuel n’a lieu, n’est toujours pas connue. Nous avons montré précédemment que le changement de type sexuel peut être induit chez C. glabrata en exprimant l’endonucléase responsable de ce mécanisme chez S. cerevisiae et que cela était lié à une très forte létalité cellulaire. Dans ce travail, nous avons étudié le lien qui existe entre changement de type sexuel et forte létalité chez C. glabrata
Mating-type switching is one of the strategies developed by fungi to promote sexual reproduction and propagation. This mechanism enables one haploid cell to give rise to a cell of the opposite mating-type so that they can mate. It has been extensively studied in the sexual yeast Saccharomyces cerevisiae but little is known about why the mating-type switching components have been conserved in species like Candida glabrata, in which neither sexual reproduction nor mating-type switching is observed. We have previously shown that mating-type switching can be triggered, in C. glabrata, by expression of the endonuclease responsible of this mechanism in S. cerevisiae, but this leads to massive cell death. In this work, we studied the link existing between mating-type switching and cell death in C. glabrata
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Arboleda, William Andrés López. "Variabilidade genética e avaliação de sensibilidade a fungicidas em sclerotinia sclerotiorum proveniente de cultivo irrigado de feijoeiro." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/7818.

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Sclerotinia sclerotiorum is a phytopathogenic fungus that infects more than 400 plant species, including common bean. Genetic variability studies in connection with phenotypic traits of agronomic interest are important to drive the control strategies against this pathogen. The aims of this study were: to evaluate the genetic variability, fungicide sensitivity, aggressiveness and to determine the proportion of MAT (Mating Type) alleles of 79 isolates of S. sclerotiorum distributed in four populations from common bean. Two populations represented a single sampling location in two different times (2000 and 2013 growing seasons). To evaluate the fungicide sensitivity a cell viability test based on the alamarBlue dye using mycelial growth was standardized. Dose-response curves for fluazinam, procymidone and benomyl were estimated using this test and were compared with dose-response curves estimated by the mycelial growth inhibition on PDA plate and the FRAC (Fungicide Resistance Action Committee) protocol. Despite the differences to assess the fungicide sensitivity between the three methods, the dose-response curves showed similar trends for the three fungicides. The fungicide sensitivity assessment at the four populations showed low sensitivity to benomyl in the Planaltina population. Furthermore, this population presented a principally clonal population structure, with a haplotype represented by 18 out of 20 isolates. Significant population differentiation in all pairwise comparisons of phi, except the comparison between EV_2013-NH, was detected. Five genetically homogeneous groups were inferred by the DAPC analysis. No group was conformed by isolates from the four populations. Only two haplotypes between the two populations from the same sampling location were shared. The hypothesis of random mating was rejected at the four populations; however this hypothesis was not rejected at the two major populations inferred by the DAPC analysis. The screening of mating type locus showed a dominance of Inv+ isolates and a high proportion of Inv+/Inv- isolates (presumable heterokaryons).
Sclerotinia sclerotiorum é um fungo fitopatogênico capaz de colonizar mais de 400 hospedeiras, sendo o agente causal do mofo branco no feijoeiro. Estudos de variabilidade genética associados a características fenotípicas de interesse agronômico, como a sensibilidade a fungicidas, oferecem informações importantes para direcionar estratégias de controle sobre este patógeno. Os objetivos deste trabalho foram avaliar a variabilidade genética, sensibilidade a fungicidas e agressividade de 79 isolados de S. sclerotiorum distribuídos em quatro populações procedentes de culturas de feijoeiro em pivô central. Duas destas populações representaram um único local de coleta em duas épocas diferentes (2000 e 2013). Para avaliar a sensibilidade a fungicidas foi padronizado um teste de viabilidade celular baseado no corante alamarBlue® sobre o crescimento micelial em microplaca de 96 poços. Curvas de dose-resposta para os fungicidas fluazinam, procimidona e benomyl, usando um isolado de S. sclerotiorum, foram estimadas com este método, e comparadas com curvas de dose-resposta obtidas com os métodos de inibição do crescimento em placa e o proposto pelo Fungicide Resistance Action Committee (FRAC). Apesar das diferentes abordagens as curvas dose-resposta mostraram tendências semelhantes para os três fungicidas. A avaliação da sensibilidade a fungicidas nas quatro populações indicou uma alta insensibilidade ao benomyl na população de Planaltina. Por outro lado, a estrutura populacional foi principalmente clonal com um haplótipo representado por 18 dos 20 isolados desta população. Diferenciação populacional significativa foi detectada em todas as comparações par a par do phi, com a exceção da comparação EV-2013-NH. A analise DAPC identificou cinco grupos geneticamente homogêneos. Nenhum dos grupos esteve constituído por isolados das quatro populações. Só dois haplótipos foram compartilhados pelas populações EV_2000 e EV_2013. A hipótese de acasalamento aleatório foi rejeitada nas quatro populações, no entanto não foi rejeitada nas duas maiores populações sugeridas pelo DAPC. O screening do Mating type locus (MAT) mostrou uma prevalência de isolados Inv+ e uma alta proporção de isolados Inv+/Inv-
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Hsueh, Yen-Ping. "Sex in Cryptococcus: Signaling, Mating-type Locus Evolution and Gene Silencing." Diss., 2008. http://hdl.handle.net/10161/665.

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Fungi have a genetically controlled sex determination system, which is governed by a small, sex-specific region in the genome called the mating-type locus (MAT). In the basidiomycetous yeast Cryptococcus neoformans, the pathogen that causes cryptococcal meningitis and cryptococcosis, sex has been associated with virulence. To further understand how sex is genetically regulated in C. neoformans, we focused our studies on the evolution of the MAT locus and molecular dissection of the pheromone signaling pathway that controls sexual development. Two MAT-linked meiotic recombination hotspots that likely drove the assembly and rearrangement of MAT were identified. Fine mapping through the integration of genetic markers established that two hotspots, one on each side of the MAT locus, are located in an ~10 kb and ~5 kb region. Plotting the G + C content along MAT and the flanking regions revealed a strong association between the location of these two hotspots and a high G + C content. By deletion and insertion of the G + C rich region, we demonstrated that the high G + C rich region is required but not sufficient to induce recombination. On the other hand, to provide direct experimental evidence to support the previously proposed model for the evolution of MAT, we sought to recapitulate the ancestral tetrapolar, and the intermediate tripolar mating systems of C. neoformans by manipulating the MAT structure to model a tetrapolar system. In the two modified "a" and "α" strains, the sex-determining genes SXI1α or SXI2a residing at the MAT locus were disrupted and the wild-type allele of these two genes was then reintroduced at another genomic location (URA5) that is unlinked to MAT. Our results show that C. neoformans can complete the sexual cycle with a tetrapolar mating configuration and the transitional tripolar state might be under strong negative selection pressure, which could have facilitated the transition from a tripolar state to the final bipolar mating system.

The MAT locus is the major determinant of the sexual identity of a cell, but several signaling pathways, including the pheromone signaling pathway, are required to regulate mating and sexual development. Many components of the pheromone signaling pathway have been identified; however, it is less clear what lies upstream of the MAPK cascade. To address this question, we studied the role of two Gα subunits (Gpa2, Gpa3) in mating and concluded that they share both redundant and divergent roles in mating. gpa2 gpa3 double mutants, but neither gpa2 nor gpa3 single mutants, are sterile in bilateral crosses. In their GTP-bound form, they signal in opposition: Gpa2 promotes mating whereas Gpa3 inhibits. Furthermore, we also studied the functions of a novel upstream component Cpr2, a pheromone receptor-like gene, in pheromone signaling and sexual development. All lines of evidence suggest that Cpr2 is a constitutive ligand-independent receptor that, when expressed, engages the same G-proteins and activates the same pheromone signaling pathway as the canonical ligand-activated pheromone receptors. Expression of Cpr2 is induced post cell fusion during mating, and likely introduces a positive feedback loop to allow a self-perpetuating signaling state to enable efficient mating. Cells lacking this receptor are fertile, but produce abnormal filamentous structures. Overexpression of CPR2 in a or α cells strongly enhances fruiting, an alternative same-sex mating process in C. neoformans. Therefore, Cpr2 establishes a new paradigm for a naturally occurring constitutively active GPCR that governs cell fate in fungi.

Finally, we described a sex-induced silencing (SIS) phenomenon in C. neoformans. Using genetic approaches, we showed that SIS is triggered by a tandem insertion of a transgene during the sexual cycle. Interestingly, only a proportion of progeny carrying the transgene are silenced. Gene deletion, RIP, or DNA methylation do not contribute to SIS but the RNAi machinery is required. In conclusion, these studies provide further understanding of sex in C. neoformans from different perspectives, which invites comparisons to other fungal and even more broadly, eukaryotic pathogens to address the role of sex in evolution.


Dissertation
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Book chapters on the topic "Mating type locus"

1

Stanton, Brynne C., and Christina M. Hull. "Mating-Type Locus Control of Cell Identity." In Sex in Fungi, 59–73. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555815837.ch4.

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2

Fraser, James A., Yen-Ping Hsueh, Keisha M. Findley, and Joseph Heitman. "Evolution of the Mating-Type Locus: The Basidiomycetes." In Sex in Fungi, 19–34. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555815837.ch2.

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3

Soll, David R. "The Mating-Type Locus and Mating of Candida albicans and Candida glabrata." In Molecular Principles of Fungal Pathogenesis, 89–112. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555815776.ch7.

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4

Bölker, M., M. Urban, S. Lauenstein, R. Lurz, and R. Kahmann. "Genetical and Functional Organization of the a Mating Type Locus of Ustilago Maydis." In Advances in Molecular Genetics of Plant-Microbe Interactions, Vol. 2, 335–39. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-017-0651-3_36.

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5

James, Timothy Y. "Analysis of Mating-Type Locus Organization and Synteny in Mushroom Fungi: Beyond Model Species." In Sex in Fungi, 317–31. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555815837.ch19.

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6

Hsueh, Yen-Ping, Banu Metin, Keisha Findley, Marianela Rodriguez-Carres, and Joseph Heitman. "The Mating-Type Locus of Cryptococcus: Evolution of Gene Clusters Governing Sex Determination and Sexual Reproduction from the Phylogenomic Perspective." In Cryptococcus, 139–49. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555816858.ch11.

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7

NOVOTNY, CHARLES P., MARY M. STANKIS, CHARLES A. SPECHT, HUILING YANG, ROBERT C. ULLRICH, and LUC GIASSON. "The Aα Mating Type Locus of Schizophyllum commune." In More Gene Manipulations in Fungi, 234–57. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-12-088642-5.50017-x.

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8

Hartl, Daniel L. "Organization of Genetic Variation." In A Primer of Population Genetics and Genomics, 21–46. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198862291.003.0002.

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Abstract:
Chapter 2 deals with the manner in which genetic variation is organized in random-mating populations, including such basics as the Hardy–Weinberg principle, multiple alleles and DNA typing, and X-linkage. These are basic, elementary concepts that set the stage for later chapters. It also includes detailed examination of two-locus linkage disequilibrium (LD), measures of LD, and the levels of LD observed in natural populations. The chi-square test for goodness of fit is discussed, together with its interpretation, along with the basics of hypothesis testing including type I error (false positive), type II error (false negative), power, and the need to correct for multiple comparisons. Also discussed are LD due to population admixture and Wahlund’s principle.
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