Sexual Adhesion Protiens as the Mechanism for Sexual Selection in S. Paradoxus

Birds do it with plumage and songs, frogs do it with mating calls, and flowers do it with pollen compatibility, but how do yeast choose appropriate mates? While speciation has been heavily studied in macro-organisms (plants and animals), very little work has been done on the study of speciation of sexually reproducing micro-organisms. My honors project will test one possible mechanism for mate selection and reproductive isolation (key steps in speciation) in the sexually reproducing yeast Saccharomyces paradoxus. It was long assumed that most micro-organisms form essentially global, mixed populations and do not undergo speciation in the classical sense. Recent studies, however, have determined that not only does S. paradoxus form distinct populations, but actually has actually evolved assortative mating – preferentially mating with members of its own population while avoiding members of other less-compatible populations. Sexual adhesion proteins are a possible mechanism for this behavior. To test this hypothesis, I will genetically engineer strains of S. paradoxus to express sexual adhesion genes from different populations, and then determine if they have a significant effect on mate choice. In investigating the mechanism underlying the mating behavior of S. paradoxus, I hope to help develop our understanding of speciation in micro-organisms.

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