Compositional changes in the venom repertoire of the blueberry stem gall wasp, Hemadas nubilipennis

The blueberry stem gall wasp (BSGW), Hemadas nubilipennis (Hymenoptera: Pteromalidae), initiates stem galls on native low- and high-bush blueberries (Vaccinium spp.) in North America, however in the last decade it has become a pest of cultivated blueberries reaching outbreak densities in western Michigan. Currently, the ecological and/or genetic mechanism(s) that facilitated this outbreak are unknown. BSGW initiates gall growth by injected an egg and venom into an actively growing stem causing shoot growth to immediately terminate, thereby reducing the production of fruit buds and causing significant reductions in crop yield. But not all varieties of blueberries are susceptible to BSGW, with resistant plants displaying a hypersensitive plant response immediately following oviposition. In this study, we determine if changes in the expression and composition of effector molecules in the venom gland of BSGW that could have contributed to the outbreak on cultivated blueberry varieties and if BSGW is adapting to individual blueberry strains by comparing the gene expression profiles of BSGW from high and low susceptible cultivated blueberry varieties. Additionally, by comparing the venom composition of BSGW to other pteromalid wasps, we can provide some insights in the evolution of galling, as BSGW is one of a handful of species to transition from a parasitoid to plant galler in the family Pteromalidae.