At Therese Markow's lab in the Ecology and Evolutionary Biology on the University of Arizona's campus, researchers are working to unlock the secret of rapid reproductive protein evolution. Alex Menayas, a UBRP student, and Erin Kelleher, a PhD candidate, are heading a venture that looks for co-evolutionary patterns based on interactions between male and female reproductive proteins.

Genes involved in sexual reproduction often evolve rapidly in a broad range of organisms, including humans. Because interactions between the male ejaculate and the female reproductive tract are determinants of male reproductive success, this pattern is likely due to sexual selection. Interestingly, research is beginning to tell the tale of a more interactive evolution where females are not simply the vessels for the fittest male sperm, but rather are active participants who determine which ejaculates compete best in their facilities. According to ongoing research from Kelleher, "observation of adaptive evolution in several female reproductive tract proteins indicates they are active players in the evolution of reproductive tract interactions."

Recently, Kelleher and collaborators identified approximately 31 genes expressed in lower female reproductive tracts of the fruit-fly D. arizonae that are candidates for molecular coevolution with components male ejaculate. If these proteins are coevolving with the male ejaculate it is predicted that natural selection will cause them to change rapidly over short evolutionary time periods. As a refresher, DNA is made up of four nucleotides, G A T C, that combine in groups of three to form the basic twenty amino acids. These amino acids are quite literally the building blocks of life that create proteins. By identifying differences in DNA sequences, it is therefore possible to explore the evolutionary history of the encoded protein.

Menayas has been sequencing two candidate genes from multiple individuals of D. arizonae and its closely related sister-species D. mojavensis. The first protein is a putative inorganic transporter, which likely moves solutes such as sodium or potassium across cell membranes in Drosophila females. Data thus far suggests that although most of this protein is highly conserved between individuals and species, certain parts of the proteins have experienced selected changes in amino acid composition. In contrast, the function of the second gene is completely unknown. The sequence data however, indicate rapid evolutionary change both within and between species. This suggests a highly dynamic protein involved in an important reproductive tract interaction, making this protein an excellent candidate for a coevolutionary relationship with males.

Prior to this project's inception, almost all of the studies on reproductive protein evolution in fruit flies were done on males, making it difficult for researchers to confidently answer difficult questions. By looking at the whole system, the team hopes to develop a more conclusive evolutionary path for this model reproductive system and apply that knowledge to other organisms and help in understanding how life has adapted to sex, at least on the microscopic scale.

Alex Menayas, UBRPer in Dr. Therese Markow's lab, Ecology & Evolutionary Biology