Isolation of the mating-type genes of the phytopathogenic fungus Magnaporthe grisea using genomic subtraction.
Using genomic subtraction, we isolated the mating-type genes (Mat1-1 and Mat1-2) of the rice blast fungus, Magnaporthe grisea. Transformation of M. grisea strains of one mating type with a linearized cosmid clone carrying the opposite mating-type gene resulted in many "dual maters," strains that contain both mating-type genes and successfully mate with Mat1-1 and Mat1-2 testers. Dual maters differed in the frequency of production of perithecia in pure culture. Ascospores isolated from these homothallic crosses were either Mat1-1 or Mat1-2, but there were no dual maters. Most conidia from dual maters also had one or the other of the mating-type genes, but not both. Thus, dual maters appear to lose one of the mating-type genes during vegetative growth. The incidence of self-mating in dual maters appears to depend on the co-occurrence of strains with each mating type in vegetative cultures. In rare transformants, the incoming sequences had replaced the resident mating-type gene. Nearly isogenic pairs produced from three M. grisea laboratory strains were mated to investigate their fertility. One transformant with switched mating type appears to have a mutation that impairs the development of asci when its mating partner has a similar genetic background. The M. grisea Mat1-1 and Mat1-2 genes are idiomorphs approximately 2.5 and 3.5 kb in length, respectively.
Kang
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DuPont Company, Wilmington, Delaware 19880-0402.
Chumley
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D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development; D015139:Blotting, Southern; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D004271:DNA, Fungal / Q000032:analysis; D005298:Fertility; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D012275:Oryza / Q000382:microbiology; D015183:Restriction Mapping; D013172:Spores, Fungal
D004271:DNA, Fungal