Whole genome screen reveals a novel relationship between Wolbachia and Drosophila host translation

Wolbachia is an intracellular bacterium that infects a remarkable range of insect hosts. Insects such as mosquitos act as vectors for many devastating human viruses such as Dengue, West Nile, and Zika. Remarkably, Wolbachia infection provides insect hosts with resistance to many arboviruses thereby rendering the insects ineffective as vectors. To utilize Wolbachia effectively as a tool against vector-borne viruses a better understanding of the host-Wolbachia relationship is needed. To investigate Wolbachia-insect interactions we used the Wolbachia/Drosophila model that provides a genetically tractable system for studying host-pathogen interactions. We coupled genome-wide RNAi screening with a novel high-throughput fluorescence in situ hybridization (FISH) assay to detect changes in Wolbachia levels in a Wolbachia-infected Drosophila cell line JW18. 1117 genes altered Wolbachia levels when knocked down by RNAi of which 329 genes increased and 788 genes decreased the level of Wolbachia. Validation of hits included in depth secondary screening using in vitro RNAi, Drosophila mutants, and Wolbachia-detection by DNA qPCR. A diverse set of host gene networks was identified to regulate Wolbachia levels and unexpectedly revealed that perturbations of host translation components such as the ribosome and translation initiation factors results in increased Wolbachia levels both in vitro using RNAi and in vivo using mutants and a chemical-based translation inhibition assay. This work provides evidence for Wolbachia-host translation interaction and strengthens our general understanding of the Wolbachia-host intracellular relationship.\n\nAuthor summaryInsects such as mosquitos act as vectors to spread devastating human diseases such as Dengue, West Nile, and Zika. It is critical to develop control strategies to prevent the transmission of these diseases to human populations. A novel strategy takes advantage of an endosymbiotic bacterium Wolbachia pipientis. The presence of this bacterium in insect vectors prevents successful transmission of RNA viruses. The degree to which viruses are blocked by Wolbachia is dependent on the levels of the bacteria present in the host such that higher Wolbachia levels induce a stronger antiviral effect. In order to use Wolbachia as a tool against vector-borne virus transmission a better understanding of host influences on Wolbachia levels is needed. Here we performed a genome-wide RNAi screen in a model host system Drosophila melanogaster infected with Wolbachia to identify host systems that affect Wolbachia levels. We found that host translation can influence Wolbachia levels in the host.