Laurie Tompkins - US grants

Drosophila melanogaster males perform courtship; females produce pheromones which cause them to be sexually attractive. The ability to perform courtship is determined by the presence of one X chromosome in parts of th central nervous system; for pheromone production, there must be two X chromosomes in tissues within the abdomen. Mutations in the Sex-lethal (Sx1) gene perturb sex determination and dosage compensation, two responses to the number of X chromosomes in cells, and affect the ability of diplo-X flies to perform and elicit courtship. This proposal describes the analysis of the effects of Sxl mutations on tissues which must be haplo- or diplo-X for sexual behaviors. Since the Sx1 mutations are temperature-sensitive, temperature-shift experiments will reveal times at which Sx1 gene function affects the nervous system and addominal tissues. In addition, the question of where the Sx1 gene acts in the nervous system can be answered by determining whether clones of mutant tissue in parts of the brain which must be haplo-X for courtship are necessary and sufficient for the performance of courtship by diplo-X flies. The effect of Sx1 mutations on pheromone-producing tissues can be ascertained by observing the responses of mutant males with olfactory defects to diplo-X flies with Sx1 mutations and to volatile compounds extracted from Sx1 flies. Another sexual behavior, courtship of young males, has not been well-characterized behaviorally. Young males produce pheromones which stimulate courtship; mature males, which are not sexually attractive, produce courtship-inhibiting pheromones and also perform rejection behaviors in response to courting males. By observing the behavior in response to males of various ages of mutant males with olfactory and visual defects, it will be possible to identify the sequence of changes which occur in the sex appeal of males as they age. These studies will eventually facilitate identification of genes which control these aspects of sexual maturation in males. The long-range goal of these experiments is to elucidate the genetic control of sexual behavior in Drosophila, with particular emphasis on behaviors which involve production or responses to sex pheromones. This work may eventually have practical for biological control. Although D. melanogaster is not an agricultural pest, its behavior is typical of non-social insects and it can thus be considered a model system.

The long-term objectives of this research are to elucidate the role of the Sex-lethal gene in regulating reproductive behavior in Drosophila males and females and to understand the function of homosexual courtship in this species. Mutations in the Sex-lethal gene, which has a primary role in sex determination, affect diplo-X flies' ability to perform and elicit courtship. The proposed experiments will reveal the role of the Sex-lethal gene in regulating specific aspects of sex pheromone synthesis in females and the visual stimuli that are associated with attractive female flies. Other mutations in the Sex-lethal gene affect haplo-X flies' ability to discriminate between attractive and unattractive flies and to avoid the courtship of normal mature males. Experiments are proposed to identify aspects of sex pheromone synthesis that are regulated by the Sex-lethal gene in males and to identify female-specific Sex-lethal transcripts that interfere with males' ability to distinguish attractive females from unattractive males. Other experiments are proposed to analyze experience-dependent courtship modification, a phenomenon that has apparently evolved to limit the performance of reproductively wasteful homosexual courtship in this species. One set of experiments will reveal the stimuli that a courting male must perceive for experience-dependent courtship modification. In addition, parts of the nervous system that must function normally for a male's homosexual courtship to be limited will be revealed by analysis in genetic mosaics of the silver mutation, which affects courting males' ability to limit their homosexual courtship. Finally, the extent to which homosexual courtship and mechanisms for limiting its occurrence are characteristic of the genus will be determined by monitoring the behavior of other Drosophila species. These experiments will further our understanding of reproductive behavior in insects, which has obvious implications for biological control of agricultural pests.

IBN-9317589 Tompkins Abstract Hawaiian Drosophila species appear to have evolved very rapidly. This research project, at the interface of chemistry and biology, investigates the extent to which the chemical communication systems of the Hawaiian species have diverged from those of their continental counterparts. Pheromones are chemicals synthesized by one individual that affect the behavior of another individual. Dr. Laurie Tompkins, a biologist at Temple University, and Dr. Larry L. Jackson, a chemist at Montana State University, are investigating the pheromones of a Hawaiian Drosophila species, D. adiastola. This species is of particular interest because males raise their abdomens over their heads, emitting droplets of fluid, while performing courtship in response to females. Drs. Tompkins and Jackson have discovered species-specific chemical compounds in the males' droplets. Moreover, females of this species will mate only with D. adiastola males, and they can distinguish D. adiastola males from males of other, closely related species even if they cannot see the males. These observations suggest that perception of the chemicals in males' droplets enables females to distinguish different males. Accordingly, Drs. Tompkins and Jackson will attempt to identify the pheromones in males' droplets. Drs. Tompkins and Jackson have also shown that waxy compounds on the cuticle ("skin") of D. adiastola females, many of which are species-specific, stimulate males to court the females and enable them to distinguish D. adiastola females from females of another, closely related species. The researchers will attempt to identify the compounds on females' cuticles that enable males to tell different females apart. In addition, since some of the waxy compounds on males' cuticles are species- specific, the researchers will try to determine whether or not any of these compounds acts as a pheromone.