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

Abstract

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.

Trends in symbiont-induced host cellular differentiation

“…A recent cell-based genome-wide RNAi screen in D. melanogaster cells infected with the wMel strain of Wolbachia found that bacterial density, or titer, increases when host ribosomal and translation initiation proteins are knocked down. This suggests that Wolbachia interacts with some of these factors in wild-type cells to alter host translation (Grobler et al 2018). This is fascinating given the trends we reported in the previous section, which found that generally only highly virulent pathogens interfere with host translation.…”

“…This is fascinating given the trends we reported in the previous section, which found that generally only highly virulent pathogens interfere with host translation. Supporting a role for translation interference in Wolbachia nutrition, this (Grobler et al 2018) and another cell screen (White et al 2017), found that Wolbachia titer decreased when host ubiquitination was inhibited. Furthermore, White et al (2017) found that Wolbachia infection significantly increases ubiquitination levels in the host cell.…”

Wolbachia and Sirtuin-4 interaction is associated with alterations in host glucose metabolism and bacterial titer

“…This reliance on host processes has led to the link of many metabolic pathways as essential in regulating Wolbachia density within the host. Despite the initial belief that consumption of host amino acids by Wolbachia was via ERAD-driven proteolysis [ 84 ], recent work suggests that amino acids are obtained from the core proteasome by bacteria strategically positioned between the ER and the Golgi [ 109 , 110 ]. This is only one of many ways by which Wolbachia seems to be interacting with host metabolic processes.…”

Transcriptome responses to elevated CO2 level and Wolbachia‐infection stress in Hylyphantes graminicola (Araneae: Linyphiidae)

“…B). This is in accordance with previous studies indicating that hosts infected with Wolbachia exhibit high levels of proteasome activity to support maintenance of Wolbachia for optimal survival (Fallon & Witthuhn, ; White et al ., ; Grobler et al ., ), such as Wolbachia competing with its host for amino acids (Caragata et al ., ).…”