title: Direct repeat-mediated DNA deletion of the mating type MAT1-2 genes results in unidirectional mating type switching in Sclerotinia trifoliorum.
abstract: The necrotrophic fungal pathogen Sclerotinia trifoliorum exhibits ascospore dimorphism and unidirectional mating type switching - self-fertile strains derived from large ascospores produce both self-fertile (large-spores) and self-sterile (small-spores) offsprings in a 4:4 ratio. The present study, comparing DNA sequences at MAT locus of both self-fertile and self-sterile strains, found four mating type genes (MAT1-1-1, MAT1-1-5, MAT1-2-1 and MAT1-2-4) in the self-fertile strain. However, a 2891-bp region including the entire MAT1-2-1 and MAT1-2-4 genes had been completely deleted from the MAT locus in the self-sterile strain. Meanwhile, two copies of a 146-bp direct repeat motif flanking the deleted region were found in the self-fertile strain, but only one copy of this 146-bp motif (a part of the MAT1-1-1 gene) was present in the self-sterile strain. The two direct repeats were believed to be responsible for the deletion through homologous intra-molecular recombination in meiosis. Tetrad analyses showed that all small ascospore-derived strains lacked the missing DNA between the two direct repeats that was found in all large ascospore-derived strains. In addition, heterokaryons at the MAT locus were observed in field isolates as well as in laboratory derived isolates.
authors.affiliation: Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Liangsheng
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Jardini
authors.affiliation: Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA.|USDA-ARS, Grain Legume Genetics and Physiology Research Unit, Washington State University, Pullman, WA 99164, USA.
authors.forename: Weidong
authors.initials: W
authors.lastname: Chen
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics* / Q000378:metabolism; D021901:DNA, Intergenic / Q000235:genetics / Q000378:metabolism; D049770:Genes, Mating Type, Fungal; D056426:Genetic Loci; D016681:Genome, Fungal; D059765:Homologous Recombination; D008540:Meiosis; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D017384:Sequence Deletion; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D021901:DNA, Intergenic