Proteins present in the seminal fluid of Drosophila melanogaster (accessory gland proteins Acps) contribute to female postmating behavioral changes, sperm storage, sperm competition, and immunity. Consequently, male-female coevolution and host-pathogen interactions are thought to underlie the rapid, adaptive evolution that characterizes several Acp-encoding genes. We propose that seminal fluid proteases are likely targets of selection due to their demonstrated or potential roles in between-sex interactions and immune processes. We use within- and between-species sequence data for 5 predicted protease-encoding Acp loci to test this hypothesis. Our polymorphism-based analyses find evidence for positive selection at 2 genes, both of which encode predicted serine protease homologs. One of these genes, CG6069, also shows evidence for consistent selection on a subset of codons over a deeper evolutionary time scale. The second gene, CG9997, was previously shown to be essential for normal sperm usage, suggesting that sexual selection may underlie its history of adaptation.

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Molecular Biology and Evolution
Department of Biology

Wong, A, Turchin, M.C. (Michael C.), Wolfner, M.F. (Mariana F.), & Aquadro, C.F. (Charles F.). (2008). Evidence for positive selection on Drosophila melanogaster seminal fluid protease homologs. Molecular Biology and Evolution, 25(3), 497–506. doi:10.1093/molbev/msm270