A new gene affecting the efficiency of mating-type interconversions in homothallic strains of Saccharomyces cerevisiae.
Homothallic strains of Saccharomyes cerevisiae are able to switch efficiently from one mating genotype to another. From a single haploid spore arise both a and mating type cells, which then self-mate to produce a colony consisting almost exclusively of nonmating a/ diploid cells. We have isolated a mutant homothallic strain that gives rise to colonies that show bisexual mating behavior. The mating reaction is always asymmetric, that is, in some colonies a mating is much stronger than mating, while others show greater than a mating.-This mating phenotype arises from the presence of three cell types in a colony: some a/ nonmating diploids and an unequal number of a and haploid cells. The predominant haploid type is that of the original cell that gives rise to the colony. This mixture of cell types arises from a very reduced efficiency of homothallic mating-type interconversions in the mutant strain.-The mutation, designated switch (swi1-1), behaves as a single genetic locus. The mutation is centromere linked, but not linked to the mating type locus or to any of the homothallism genes: HO, HMa and HM. The switch mutation does not affect the efficiency of self-mating, but rather directly affects the frequency of interconversion of mating types.
Haber
J E
JE
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02154, USA.
Garvik
B
B
D049770:Genes, Mating Type, Fungal; D005812:Genes, Switch; D006238:Haploidy; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D013172:Spores, Fungal