A potential role for the interaction of Wolbachia surface proteins with the Drosophila microtubulin in maintenance of endosymbiosis and affecting spermiogenesis

Wolbachia, as a widely infected intracellular symbiotic bacterium in Arthropoda, is able to manipulate the reproduction of insect hosts for facilitating their own transmission. Cytoplasmic incompatibility (CI) is the most common phenotype that Wolbachia induced in insect hosts where they resulted in the failure of uninfected egg hatch when fertilized with the sperm derived from Wolbachia-infected males, suggesting that the sperm are modified by Wolbachia during spermatogenesis. Although the molecular mechanisms of CI are beginning to be understood, the effects of Wolbachia on the symbiotic relationship and the proper dynamics of spermatogenesis have not yet been fully investigated. We report here that Wolbachia infection induced a significant upregulation of betaTub85D in the testis of Drosophila melanogaster. Knockdown of betaTub85D in fly testes resulted in significant decrease in the copy number of Wolbachia surface protein gene (wsp), indicating a notable reduction of Wolbachia density. Pull-down analyses revealed that WSP interacted with the betaTub85D of D. melanogaster. Wolbachia infection altered the interactome between betaTub85D and other proteins in the testes, and may thus change the protein synthesis and metabolic pathways. Wolbachia infection induced not only an interaction of betaTub85D with Mst77F but also increase in phosphorylated Mst77F. These results suggest that Wolbachia WSP protein might play important roles in anchoring the endosymbiont to the host's cytoskeleton and consequently interfere the interactions among key proteins involved in spermatogenesis in the insect host testes, resulting in modified sperm.