Hamilton, W. C.; Massey, J.; Hardy, E.; Lopez-Madrigal, S.; Phelps, M.; Martin, M.; Newton, I. L. G.

Arthropods, the most diverse phylum on Earth, are hosts to a plethora of bacterial parasites that secrete various toxins of unknown function during infection. The most prevalent of these is the intracellular bacterium Wolbachia pipientis. The microbe infects between 40-60% of insect species, causes important reproductive manipulations, and limits virus replication in arthropod vectors, becoming a promising biocontrol agent. Understanding the molecular basis of Wolbachia infection and Wolbachia-induced phenotypes is critical to the use of Wolbachia in vector control. These Wolbachia ankyrin repeat proteins (WARPs) represent a highly dynamic and diverse part of the Wolbachia pangenome and remain thus far, largely uncharacterized. Here, we perform molecular and genetic screens to identify interactions between WolbachiawMel WARPs and their target host proteins in Drosophila melanogaster Our results identify strong interactions of two Wolbachia proteins, WARP434 and WARP754, with two host targets (CG11327 and Ptp61F, respectively). Heterologous expression of these two WARPs is extremely toxic in Drosophila tissues and the toxicity is dependent on the ankyrin repeat domain of each WARP. Importantly, knockdown of the host targets alleviates toxicity, confirming WARP/target interactions. Finally, antibodies targeting both WARPs show expression by Wolbachia during infection of Drosophila cells. Understanding how Wolbachia manipulates its host biology and which host pathways it targets during infection will help us divine how the most prevalent intracellular bacterial parasite on Earth interacts with its insect hosts at the molecular level. Our screen is the first step towards that goal.