| Little is known about the developmental genetic origin of innate behaviors in any animal. Here, I use the model system Drosophila melanogaster , the vinegar fly, in order to dissect the genetic basis of stereotyped male courtship behavior. I concentrate on the yellow gene, which disrupts a specific step in the male courtship ritual, termed wing extension. Wing extension is a fixed action pattern, and a decrease in wing extension results in a decrease in male courtship song, which in turn decreases male mating success. In the first chapter, I review the literature concerning the relationship between yellow and male mating success. I then use behavioral and classical genetic methods to test 12 hypotheses for why yellow mutant males have poor mating success, and only find convincing evidence for one—that yellow is necessary for normal amounts of wing extension. In the second chapter I use developmental genetic and biochemical methods to demonstrate that yellow is downstream of fruitless in the D. melanogaster sex determination pathway in the developing central nervous system. I also show that yellow function in the central nervous system at a single developmental stage is sufficient to restore normal levels of courtship song singing. In the third chapter, I dissect the yellow gene at molecular genetic level in relation to behavior. I map a 200 base pair region upstream of the first exon of yellow whose function is necessary for normal male mating success. This region is likely to bind specific proteins which regulate yellow expression relevant to male courtship behavior. Finally, in this third chapter I develop a novel hypothesis concerning the function of the yellow protein product in the development of sexual behavior. This hypothesis, that Yellow acts as a growth factor/hormone, binds to a receptor, and regulates a second messenger pathway, has the potential to explain the role of yellow in the pigmentation process as well. Overall, this dissertation comprises a significant contribution towards understanding the construction of D. melanogaster male sexual behavior, particularly in relation to the yellow gene, on behavioral, genetic, and neurobiological levels of study. |
