Haploinsufficiency of the sex-determining genes at MAT α restricts genome expansion in Saccharomyces cerevisiae

Kazumasa Oya; Akira Matsuura

doi:10.1016/j.isci.2022.104783

Haploinsufficiency of the sex-determining genes at MAT α restricts genome expansion in Saccharomyces cerevisiae

iScience. 2022 Jul 19;25(8):104783. doi: 10.1016/j.isci.2022.104783. eCollection 2022 Aug 19.

Authors

Kazumasa Oya¹, Akira Matsuura²

Affiliations

¹ Department of Biology, Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi-chou, Inage-ku, Chiba 263-8522, Japan.
² Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoi-chou, Inage-ku, Chiba 263-8522, Japan.

Abstract

In Saccharomyces cerevisiae, mating type of haploid cells is determined by the presence or absence of the MATα idiotype containing MATα1 and MATα2, which encode the transcription factors. These proteins are characterized by rapid turnover, but the physiological relevance of this property remains unclear. Here, we show a direct link between their intracellular levels and sexual stability. Polyploid cells with fewer MATα copies had unstable sexual phenotypes, causing morphological changes and an increase in cell death; these effects were mediated by hyperactivation of the mating pheromone response pathway. Thus, the MATα1 and MATα2 genes are haploinsufficient genes, and the reduction in their product levels causes sex fluctuation. Chromosome III harboring the mating type locus is the most prone to loss in diploids. We propose that the haploinsufficiency of MATα compensates for the drop-out prone nature of chromosome III, thereby suppressing speciation through increased genome size via polyploidization.

Keywords: Biological sciences; Evolutionary biology; Evolutionary mechanisms; Microbial genetics; Microbiology.