摘要：SummaryInSaccharomyces cerevisiae, mating type of haploid cells is determined by the presence or absence of theMATα idiotype containingMATα1andMATα2, 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 fewerMATα 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, theMATα1andMATα2genes 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 ofMATα compensates for the drop-out prone nature of chromosome III, thereby suppressing speciation through increased genome size via polyploidization.Graphical abstractDisplay OmittedHighlights•Polyploid cells with reducedMATα copies show abnormal morphology and increased death•These phenotypes are due to hyperactivation of the mating pheromone response pathway•Quantity of theMATα products is important for stable sexual phenotype•This property may be involved in the suppression of speciation via polyploidizationBiological sciences; Microbiology; Microbial genetics; Evolutionary biology; Evolutionary mechanisms.
