Mechanisms of Wolbachia intracellular accumulation in somatic cells of the Drosophila ovary. Ajit Kamath, Eva Fast, Michelle Toomey, Horacio Frydman. Biology, Boston University, Boston, MA.

   Wolbachia are obligatory intracellular bacteria infecting up to 70% of insect species. Many of these insects are vectors for the transmission of devastating tropical diseases. Wolbachia mainly propagates by vertical transmission via the female oocyte. They are under selective pressure to reach the female germline and infect the next generation. However the Wolbachia infection is not limited just to the germline cells, but also several somatic cell populations have been shown to have higher Wolbachia loads compared to surrounding tissue, including stem cell niches, neurons, trachea and malpighian tubes. The different mechanisms underlying the higher intracellular loads are unknown. In terms of stem cell niche tropism, we have shown that targeting of different niches is determined by Wolbachia intrinsic factors. However, another possible means for a specific cell type to display higher Wolbachia levels is through lower mitotic rates compared to the surrounding cells. Here we show that within the follicular epithelium, the polar cells (PC) have higher levels of intracellular Wolbachia accumulation. After PC specification, the surrounding follicular epithelium retains mitotic activity until stage 6 of oogenesis. Using this system we can follow all the stages of the polar cell development allowing us to investigate the kinetics of the intracellular accumulation of Wolbachia in the polar cells and the surrounding follicular epithelia. This analysis will provide us mechanistic insights into the preferential targeting of Wolbachia to the polar cells in the Drosophila ovary.