Evolutionary And Functional Analysis Of The Drosophila Bag Of Marbles Gene

Reproduction is fundamentally important for organismal fitness. While it is critical that each step in reproduction proceed correctly, many of the genes that regulate these processes are adaptively evolving in response to both internal and external selective pressures. We have previously shown that the bag of marbles (bam) and benign gonial cell neoplasm (bgcn) genes are evolving under rapid, adaptive evolution in D. melanogaster and D. simulans. These genes act at the earliest stages of reproduction, germline stem cell (GSC) regulation. In the first study, I expand population genetic analyses to genes that play a role in GSC regulation and/or genetically interact with bam. I find that multiple GSC regulatory genes show evidence of rapid, adaptive evolution in D. melanogaster and/or D. simulans. These genes play very different roles in the regulation of GSCs, and their diverse functions and expression patterns suggest that multiple selective pressures are acting to drive the evolution of GSC regulatory genes. In a second study, I focused on bam to determine the functional consequences of bam's sequence divergence. I developed a transgenesis assay to determine the ability of a bam orthologs from D. melanogaster and D. simulans to rescue the male and female sterility of a D. melanogaster bam mutation. I found that while D. simulans can rescue D. melanogaster bam male sterility, it fails to fully rescue female sterility suggesting that the selective pressure driving the evolution of bam is present in the female germline. In the final study, I investigated the hypothesis that the bacterial endosymbiont, Wolbachia pipientis, is driving the adaptive evolution of bam. I found that Wolbachia and bam genetically interact by showing that Wolbachia can rescue the fertility defects of a bam hypomorph. I found that D. melanogaster-specific Wolbachia is unable to accumulate as well in the presence of a D. simulans bam ortholog which is consistent with a model that Wolbachia is co-evolving with bam and supports the hypothesis that Wolbachia is driving the adaptive evolution of bam