Geoffrey Findlay

Joined Program: 2005
Previous Degree: B.A. Biology, Carleton College
Swanson Lab
gfindlay (at) u.washington.edu
personal website

Research:

Across diverse taxa, seminal fluid proteins (Sfps) transferred at mating affect the reproductive success of both sexes.  Such reproductive proteins often evolve under positive selection between species; because of this rapid divergence, Sfps are hypothesized to play a role in speciation by contributing to reproductive isolation between populations.  In Drosophila, individual Sfps have been characterized and are known to alter male sperm competitive ability and female post-mating behavior, but a proteomic-scale view of the transferred Sfps has been missing. We have developed a novel proteomic method that uses whole-organism isotopic labeling to detect transferred Sfps in mated female D. melanogaster.  We identified 63 proteins previously unknown to function in reproduction and confirmed the transfer of dozens of predicted Sfps.  Relative quantification of protein abundance revealed that several of these novel Sfps are abundant in seminal fluid.  Positive selection and tandem gene duplication are the prevailing forces of Sfp evolution, and comparative proteomics with additional species revealed lineage-specific changes in seminal fluid content.  We have also used a proteomic-based gene discovery method to uncover several dozen previously unannotated genes in D. melanogaster.  Our results to date demonstrate an experimental method to identify transferred proteins in any system that is amenable to isotopic labeling, and they underscore the power of combining proteomic and evolutionary analyses to shed light on the complex process of Drosophila reproduction.

Current research is focused on three areas: a) analyzing the function of specific Sfps by using RNA interference lines; b) associating naturally occurring variation in the identified Sfps with sperm competitive phenotypes; and, c) analyzing whether any Sfps may alter female post-mating behavior by examining whether any male proteins localize to female brains after mating.  Our work continues to be carried out in collaboration with Dr. Michael MacCoss in our department, and we also work with Dr. Mariana Wolfner (Cornell University) for RNAi experiments and Dr. William Rice (UC-Santa Barbara) for the association study.