J. Dylan Shropshire, PhD
My research program spans eukaryotic and prokaryotic genetics across the host-microbe interface. Specifically, my research evaluates how maternally transmitted Wolbachia bacterial endosymbionts manipulate eukaryotic host reproduction. The most common of these manipulations is cytoplasmic incompatibility (CI), which reduces the viability of uninfected embryos fertilized by Wolbachia-modified sperm. Wolbachia-bearing females rescue CI, providing infected females a relative fitness advantage. The CI drive system spreads Wolbachia to high frequencies in natural systems and directly underlies Wolbachia remarkable biocontrol efficacy in mosquito systems to reduce human disease transmission on several continents.
Using Drosophila genetics, transgenics, microscopy, and a comprehensive molecular biology toolset, I have built a research program focused on dissecting the genetic basis of Wolbachia-induced CI. At Vanderbilt University, my PhD work revealed that two of Wolbachia’s prophage genes are necessary and sufficient to cause CI (LePage et al. 2017, Nature; Shropshire et al., 2019, PLOS Genetics), and one prophage gene rescues CI (Shropshire et al. 2018, PNAS). I also identified key residues across both proteins necessary for CI and/or rescue and functionally validated a suite of homologs that can likewise contribute to the CI phenotype (Shropshire et al. 2020, Genetics; Shropshire et al. 2020, PLOS Pathogens). The discovery of the CI genes enables a new generation of studies to disentangle the causes and consequences of reproductive parasitism in the context of genetics (Shropshire et al. 2020, eLife). Indeed, at the University of Montana, I am extending my work to determine the precise causes of CI-strength variation, which ranges from very weak to complete CI (no eggs hatch). My work is demonstrating the contributions of CI gene sequence variation, gene expression, and Wolbachia abundance in host tissues to this variation observed across insect species and developmental and environmental contexts.