Incidence of SUC-RTM telomeric repeated genes in brewing and wild wine strains of Saccharomyces.

When over-expressed, RTM yeast genes confer resistance to the toxicity of molasses. They are found in distiller's and baker's industrial yeasts in multiple copies, scattered on the telomeres and physically linked to the telomeric SUC genes. Because these genes are absent from some laboratory strains, we explored the genomes of other industrial yeasts (brewing strains) and wine wild strains. A collection of 47 wine yeast strains (S. cerevisiae and S. bayanus) and 15 brewing strains, lager, ale and possible ancestors (S. monacensis, S. paradoxus and S. carlsbergensis) were screened for the presence of RTM genes. Only three wine strains and all brewing strains proved to contain RTM sequences in different copy numbers. PCR and chromosome blotting confirm the presence of SUC sequences in tandem with RTM. Moreover, analysis of the entire S. cerevisiae genome sequence shows that three other, non-telomeric, genes related to RTM are scattered on different chromosomes.