Systematic study of evolution of sex-differentiation genes involved in speciation of Saccharomyces yeasts

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In order to clarify the mechanism of speciation in Saccharomyces yeasts, we attempted to compare sex-differentiation genes and chromosome organizations among several Saccharomyces yeasts. Research results we obtained are as follows.1.We isolated a gene encoding an alpha mating pheromone from the yeast Saccharomyces naganishii. Then, we compared the structure of the gene with that of an orthologue from a laboratory strain of the yeast Saccharomyces cerevisiae. As a result, the coding regions of these two genes extremely resembled each other. However, the 5'-upstream regulatory regions from these two genes represented species-specific divergence.2.We isolated a gene encoding a homothallism gene from a homothallic type strain of the yeast Saccharomyces paradoxus. Then, we compared the structure of the gene with that of an orthologue from a laboratory strain of the yeast Saccharomyces cerevisiae. As a result, it was shown that the coding regions and 5'-upstream regulatory regions from these two genes had coevolved through the evolutionary pathway.3.We investigated the chromosomal localization of genes involved in galactose assimilation in the yeast Saccharomyces naganishii. It was revealed that the GAL10gene was translocated from the duster of GAL genes in the S.naganishii genome. It is very unique because the fact that the GAL10 genes are included in the GAL gene clusters has been reported so far.