A polyploid population of Saccharomyces cerevisiae with separate sexes (dioecy).
Saccharomyces cerevisiae has proved to be an interesting model for studies of evolution, with whole-genome duplication shown to have played an important role in the evolution of this species. This phenomenon depends on the formation of a transient stable polyploid state. Previous studies have reported polyploidy to be an unstable state in yeast, but here, we describe a polyploid population of S. cerevisiae. The evolution of higher eukaryotes has also involved the development of different systems of sexual reproduction, the choice between self-fertilization and out-crossing becoming a key issue. Saccharomyces cerevisiae is a hermaphrodite eukaryote, despite the theoretical genetic disadvantages of this strategy, in which self-fertilization occurs. We describe, for the first time, a near-dioecious (with separate sexes) population in this species. Mating type and the MAT locus display complex segregations. Essentially, each strain produces, by meiosis, spores of only one mating type: mata or matalpha. Moreover, strains are heterothallic, and diploid nonmating clones generated from a single spore do not sporulate. These three properties limit self-fertilization and strongly favour out-crossing. We suggest that the shift in sexual strategy, from hermaphroditism to dioecy, is specific to the brewing process, which overcomes the sexual isolation probably found in natural biotopes.
Al Safadi
Rim
R
Génétique Moléculaire des levures, UMR5240, Université de Lyon, Université Lyon 1, Villeurbanne, France.
Weiss-Gayet
Michèle
M
Briolay
Jérôme
J
Aigle
Michel
M
D020090:Chromosome Segregation; D049770:Genes, Mating Type, Fungal; D008540:Meiosis; D011123:Polyploidy; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development*; D013172:Spores, Fungal / Q000235:genetics