'Alternative self-diploidization' or 'ASD' homothallism in Saccharomyces cerevisiae: Isolation of a mutant, nuclear-cytoplasmic interaction and endomitotic diploidization

Abstract

A mutant of Saccharmomyces cerevisiae representing a novel life cycle, named 'alternative self-diploidization' or 'ASD' homothallism, was obtained fortuitously. In this life cycle, MATα (or MATa) haplophase and MATα/MATα (or MATa/MATa) diplophase alternate. Germinated cells haploid and mating. They soon become nonmating and sporogenous as they vegetatively grow. They sooner or later diploidize presumably via endomitosis. The diploid cells haploidize via normal meiosis. A single recessive nuclear mutation, named asd 1-1, is responsible for 'ASD' homothallism. In the ρ0 cytoplasm, asd 1-1 cells mate even if at a low efficiency and fail to diploidize. Since pet mutation do not have such effects, we conclude that a certain mitochondrial function other than respiration is required for manifestation of 'ASD' homothallism. That is, 'ASD' homothallism is the result of some sort of nuclear-cytoplasmic interaction.