One of the goals of neuroscience is to understand how genes direct the development of the nervous system, and how sensory input from the environment interacts with the nervous system to result in behavior. Male fruit flies of the genus Drosophila carry out a complex and stereotyped courtship ritual that provides an excellent model in which to study these processes. The correct performance of this ritual is critical for success in mating and reproduction. Mutations affecting the courtship ritual typically result in slow courtship, or failure to court entirely. However, we have identified a gene (Tre1) that, when mutated, causes unusually rapid performance of the ritual. This result is unique, and suggests a previously unknown function in mating behavior: delay of courtship. This research project aims to answer two questions: first, why would a gene exist whose function appears to be to reduce the speed of mating, which would seem to put males at a disadvantage relative to males that mate more quickly? Second, in what cells does the Tre1 gene function, and what are these cells doing during courtship behavior? In addition, to increase the exposure of women and underrepresented minority students to basic scientific research, an integral component of this project is to establish a summer mentorship program that brings high school biology teachers from local minority-serving high schools, together with their students, to the lab to design and implement behavioral genetics experiments for their classrooms.
Drosophila males engage in a stereotyped courtship ritual in order to gain the favor of females. Previous research has shown that the typical result of failure to perform any of the steps correctly and in the correct order results in greatly reduced opportunities to mate. In addition, the behavioral sex determination gene fruitless (fru) has been shown to be necessary and sufficient to direct all steps of courtship behavior. Loss of the male-specific fru transcripts (fruM) typically leads to increased latency to court, inappropriate mate choice, or failure to court at all. We identified a GAL4-transgene that is inserted into the coding sequence of the Tre1 GPCR gene (Tre1-GAL4). When this GAL4 line is used to drive expression of either an RNAi targeting fruM or the feminizing transgene UAS-traF, it results in male flies that initiate courtship and achieve copulation much more quickly than control animals. This phenotype is recapitulated in males mutant for Tre1, which indicates that the Tre1 GPCR is required for normal courtship behavior. The expression pattern of Tre1-GAL4 is limited, with expression in regions consistent with olfactory reception and processing in both the peripheral and central nervous system. The activities described in this proposal identify positively the Tre1-GAL4 cells, investigate the function of those cells in courtship initiation, test the hypothesis that the Tre1-GAL4 cells are involved in mate choice, and further investigate the role of Tre1 itself in courtship initiation.
