This work will contribute to our understanding of factors affecting fertility and how differences in the interactions between sperm and the reproductive tracts contribute to the reproductive isolation of species. After leaving the testes, sperm undergo numerous changes as they move through the male and female reproductive tracts. These changes to the sperm cells, how they vary among species, and their importance for fertilization success are not well understood. This project will characterize these changes, at the molecular level, within and among closely-related species of fruit fly to understand their evolutionary history, the cause of specific changes, and the effects for sperm survival and fertilization success. This project will also result in the development of a "Genes, Genomes, and Society" (GGS) educational program to introduce high-school students to the field of genomics. It will sponsor a genomics workshop for New York High School teachers to encourage adoption of the GGS program. Finally, some high school students and teachers will also participate in laboratory research.
Using whole-cell proteomic analyses, sperm will be tracked, beginning with storage in the male seminal vesicle, through ejaculation and following protracted storage in the primary sperm-storage organ of females. Identical analyses will be conducted using two sibling Drosophila species (D. simulans and D. mauritiana) and for reciprocal hybrid matings between the species, where evolved ejaculate-female compatibility has potentially been compromised. Proteomic analyses will be similarly conducted on female reproductive tract secretions. The resulting datasets will provide, for closely related species, an exhaustive library of the sperm proteome throughout the life history of sperm, which will permit all alterations to sperm (protein gain, loss and modification) to be discerned. With regard to proteins added to sperm during storage, reciprocal sex-specific labeling will distinguish male- from female-contributed proteins. Molecular evolutionary and genomic analyses of proteins involved in sperm-female interactions, together with the data from hybrid inseminations, will address questions about rates of divergence, genetic architecture and the putative role of sperm-female interactions in speciation.
