FRY, J.D.; University of Rochester: Evolutionary and ecological genetics of ethanol tolerance in Drosophila

Many species of Drosophila breed in fermenting fruit, in which ethanol can reach toxic levels. Work by Jean David’s group in France has shown that fruit-breeding Drosophila species have higher ethanol tolerance and higher activity of the enzyme alcohol dehydrogenase (ADH) than non-fruit breeders. Among fruit-breeding species, temperate zone populations of D. melanogaster have evolved unusually high ethanol tolerance, along with a propensity to choose breeding sites high in ethanol. It is clear that D. melanogaster‘s high ethanol tolerance cannot be explained simply by an increase in ADH activity, but little is known about the other genes involved. We are attempting to identify genes that contribute to D. melanogaster‘s ethanol tolerance. Whole-genome expression profiling indicates that genes upregulated by ethanol in D. melanogaster larvae show higher constitutive expression in D. melanogaster adults than in adults of the closely related and less tolerant D. simulans. This suggests that D. melanogaster‘s high ethanol tolerance has come about in part through changes in expression level of multiple genes. We have also found evidence that variation in activity of the enzyme aldehyde dehydrogenase (ALDH) contributes to variation in ethanol tolerance within D. melanogaster. These and other leads are being investigated.