Bruce Wallace - US grants

The bulk of the research proposed in this application will deal with the kinetics of mating in Drosophila. Prime variables for each tested strain or species will be (1) time allowed for mating, (2) the volume of the mating chamber, and (3) the numbers of males and females within the chamber. The generality of the results will be ascertained by studying at least two wild strains of D. melanogaster as well as ebony and sepia strains (preliminary data on sepia are available); D. pseudoobscura, D. persimilis, and D. simulans will also be tested. These studies are intended to reveal the general, relatively simple aspects of mating kinetics in Drosophila which can be observed despite the known complexities of the courtships and other reproductive behaviors of these flies. Knowledge of the mating kinetics of single species should aid in the interpretation of observed sibling-species responses to simulated sterile-male control efforts (a separate research project). A second, special effort (to be undertaken in collaboration with Dr. Stella Crossley, a visiting professor from Monash University, Australia) will involve the mating kinetics of geographic strains of D. melanogaster (Riverside, California; Bermuda; Madeira) where it is known that the receptiveness of females and the courting aggressiveness of males differ considerably. Such strains (say, A and B) will be studied in all combinations; A x A, A x B, B x A, and B x B. The results should bear on the notion that asymmetries in the mating behaviors of the two sexes are important in the origin of the sexual isolation of newly arisen species.

The sterile-male-release program for the control of the New World screwworm, Cochliamyia hominivorax has been an enormous success; nevertheless, a resurgence of cases in Texas has occurred recently, and recalcitrant local populations that have defied eradication efforts have been encountered. Workers at the University of Texas, Austin, have recently suggested that the screwworm is not one species but, rather, a cluster of sibling species; such clusters of morphologically indistinguishable species are well known in Drosophila (flies), Anopheles (mosquitos), Rana (frogs), and other organisms. The possibility that the screwworm actually comprises several sibling species bears heavily on the sterile-male eradication program. Under the present proposal, sibling species of Drosophila would be subjected to a simulated sterile-male control program in the laboratory. (Screwworm flies, because they are a dangerous pest, cannot be studied outside a legally authorized facility.) Parameters that can be varied experimentally include: the degree of sexual isolation exhibited by the sibling-species pairs, the relative proportions of the sibling species, the ratios of released "sterile" flies to the "natives," and the densities of flies in the laboratory mating chambers. These studies should be useful in understanding the responses of screwworms in the field when challenged with overwhelming numbers of sterilized flies. The importance of the study is suggested by (1) the Latin name of the screwworm and (2) the $10-$20 million which are spent annually on screwworm control.

A joint meeting of the Population Biologists of the Northeast (PBONE) and the Southeastern Ecological Genetics Group (SEEGG) will be held at Virginia Tech on May 17/19, 1990. Formal sessions will consist of three plenary addresses by nationally known speakers from outside the PBONE-SEEGG area, 24 short talks by participants, 36 talks by workshop participants, and poster sessions. A special feature of these meetings are the invitations that have been sent to 200 or more small colleges in a 5-state area (NC-TN-KY-VA-WVA) urging that their biology professors and most promising undergraduate students (especially women and members of minority group) attend. Special field trips and other exercises planned for these invited guests; more importantly, however, is the opportunity these meetings will give these young persons for observing how their peers from larger institutions comport themselves and for these students to make contacts that may facilitate their acceptance into graduate programs.

At synapses throughout the nervous system there are structural specializations that play a direct role in synaptic transmission. The formation and maintenance of such structural specializations relies on communication between the axon terminal and its target. For example, at the vertebrate skeletal neuromuscular junction the axon terminal releases signals that direct the muscle fiber to organize postsynaptic apparatus, which includes aggregates of acetylcholine receptors (AChRs). Several lines of evidence indicate that agrin, a protein purified from the synapse- rich electric organ of the marine ray Torpedo californica, mediates the nerve-induced formation of postsynaptic specializations at embryonic and regenerating neuromuscular junctions. For example, agrin causes the formation of patches on the surface of myotubes in culture at which AChRs and other components of the postsynaptic apparatus are aggregated. Agrin also causes AChRs to be phosphorylated, a modification that could regulate receptor distribution. The goal of this project is to understand the mechanism of action of agrin at the molecular level and, in particular, to test the hypothesis that agrin-induced phosphorylation of AChRs may play a role in receptor aggregation. The specific aims are: 1. To characterize agrin-induced phosphorylation AChR phosphorylation and aggregation. 2. To compare the properties of agrin-induced AChR phosphorylation and aggregation. 3. To measure changes in AChR phosphorylation at developing neuromuscular junctions. 4. To identify the agrin receptor/kinase. 5. To search for agrin-induced phosphorylation of other proteins. The experiments outlined in this proposal involve protein chemistry, immunochemistry, and immunohistochemistry. Studies such as these are essential to understanding the molecular mechanisms of the formation of the neuromuscular junction and so may provide insights into ways to diagnose and treat developmental abnormalities or diseases of the neuromuscular system and to enhance neuromuscular regeneration after trauma.