Ethanol Sensitivity and rapid tolerance in Drosophila

Abstract

Overall, the goal of this project is to understand how the response to ethanol in males and females has diverged between species, which is an essential first step in connecting phenotypic differences in this response to molecular evolution in underlying gene networks. Drosophila is an important model organism in the study of ethanol tolerance and sensitivity. This is due to the ease of genetics in this system, the wealth of genomic knowledge and widely conserved physiological and behavioral responses. In addition, Drosophila feed on fermenting fruit and frequently encounter ethanol in their environment. While lethal effects of ethanol have been surveyed in many Drosophila species, little is known about species diversity, and sex dimorphism, of ethanol sensitivity and tolerance. This thesis set out to better understand species and sex differences in the response to ethanol. To do this, behavioral assays of sensitivity to sedating effect of ethanol, as well as tolerance to multiple exposures, were used to examine the response in males and females of fifteen Drosophila species. I find that measure of ethanol sensitivity and tolerance are highly variable. Despite this, likely environmental, variance within species there are significant differences among species including presence and absence of ethanol tolerance. Some species show statistically significant sex dimorphism individually, but differences between adult males and females using our methodology was not common. When significant sex differences were detected, they were primarily in tolerance rather than in sensitivity. To lay the groundwork for future studies of the molecular basis of these differences we examined both data from the existing literature on regulation of sex differential expression, including our own, and newly collected data on the genes downstream of fruitless a major regulator of neurological differences between sexes, as well as an essential genes in both sexes. I find that ethanol tolerance and sensitivity vary substantially across species, and in some cases differences are sex specific or dimorphic. Additionally, I identified eighty six potential candidates for the regulation of sex differences in ethanol tolerance and sensitivity that are downstream of both major branches of the sex determination pathway.