Transovarial transmission of Wolbachia bacteria via P44/Msp2-IMP2 mediated endocytosis.

Wolbachia is a maternally inherited endosymbiont that stably localizes in oocytes of arthropods to ensure successful transovarial transmission. However, the source of Wolbachia in oocytes is unclear. Here, we obtained a Wolbachia strain that is transovarially transmitted with complete fidelity in the agricultural pest spider mite Tetranychus truncatus. Using fluorescence in situ hybridization, we showed that Wolbachia migrate from the digestive cells to the reproductive system as a female develops. When Wolbachia from T. truncatus was transferred to Aedes albopictus cells, we demonstrated that its cell-to-cell spread was regulated by the host's endocytosis system. By assaying the proteome, we identified a bacterial surface protein P44/Msp2 from Wolbachia that interacted with the host's integral membrane protein 2 (IMP2). RNA interference of IMP2 indicated that it facilitated entry of Wolbachia. Our results show that Wolbachia from somatic cells contribute to its transovarial transmission, and that Wolbachia also utilize the surface protein to invade new host cells. This extends our understanding of how Wolbachia is transmitted between cells and facilitates artificial transfection work.