Enhancement of Ty transposition at the ADH4 and ADH2 loci in meiotic yeast cells.

Genome polymorphism in the yeast Saccharomyces cerevisiae is frequently the result of transposition and recombination events involving Ty elements. The activity of these retrotransposons is closely integrated with the life cycle of the host. Ty transcription is repressed in diploid, but not haploid, cells and is induced by certain stress conditions. We have found that Ty transposition at the ADH4 and ADH2 loci is not only active, but 50-fold more frequent in meiotic yeast than in mitotic cells. These data provide a further example of the success of Ty elements in maximising their own chances of spread and survival while minimising the risks to the host yeast population.