title: Rapid asymmetrical evolution of Saccharomyces cerevisiae wine yeasts.
abstract: Genetic instability causes very rapid asymmetrical loss of heterozygosity (LOH) at the cyh2 locus and loss of killer K2 phenotype in some wine yeasts under the usual laboratory propagation conditions or after long freeze-storage. The direction of this asymmetrical evolution in heterozygous cyh2(R)/CYH2(S) hybrids is determined by the mechanism of asymmetrical LOH. However, the speed of the process is affected by the differences in cell viability between the new homozygous yeasts and the original heterozygous hybrid cells. The concomitant loss of ScV-M2 virus in the LOH process may increase cell viability of cyh2(R)/cyh2(R) yeasts and so favour asymmetrical evolution. The presence of active killer K2 toxin, however, abolishes the asymmetrical evolution of the hybrid populations. This phenomenon may cause important sudden phenotype changes in industrial and pathogenic yeasts.
authors.affiliation: Departamento de Microbiología, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Ambrona
authors.forename: Antonia
authors.initials: A
authors.lastname: Vinagre
authors.forename: Manuel
authors.initials: M
authors.lastname: Ramírez
mesh_terms: D003433:Crosses, Genetic; D019143:Evolution, Molecular; D055646:Killer Factors, Yeast; D019656:Loss of Heterozygosity / Q000235:genetics; D011506:Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014920:Wine / Q000382:microbiology
chemical_list: D055646:Killer Factors, Yeast; D011506:Proteins