The cellular lives of Wolbachia

Comparative analysis ofWolbachiamaternal transmission and localization in host ovaries

“…Finally, we examined how temperature impacts cellular Wolbachia abundance at the site of germline formation in stage 10 oocytes during host oogenesis. At this stage, wMel Wolbachia localization at the posterior cortex of the oocyte is considered to be a critical step in the process of germline-to-germline Wolbachia maternal transmission 14,15,21,36,[59][60][61][62][63] . We imaged a total of 283 stage 10 oocytes from eight-day-old females reared at the two different temperatures and quantified cellular Wolbachia abundance (measured as corrected total cell fluorescence; CTCF) in the whole oocytes, the posterior region, and the posterior cortex (Figure S2) 14,15,21 .…”

“…Two Wolbachia strains (wAura and B-group wMau) exhibited minor temperature-dependent changes in transmission, but wMel stood out with a relatively large decrease in transmission as temperature dropped from 25° to 20°C (Figure 2). Maternal transmission is generally expected to depend on Wolbachia density in host reproductive tissue 20,34,43,71 , and specifically within developing oocytes 14,15,21,36,[59][60][61][62][63] . Our analyses uncovered considerable, significant variation in Wolbachia densities at the tissue level and cellular abundances in oocytes, which also often varied depending on temperature.…”

“…This includes introducing the pathogen-blocking wMel Wolbachia strain from Drosophila melanogaster into mosquito populations to reduce the incidence of dengue and other diseases on multiple continents [29][30][31][32] . Nonetheless, it is largely unknown why maternal transmission may breakdown under certain circumstances, especially for non-model systems 15,21,[33][34][35][36] .…”

“…What might underlie variable maternal transmission rates? Maternal transmission breakdown is predicted to stem from reductions in Wolbachia abundance and localization throughout host development and specifically at the critical stages of oogenesis thought to facilitate germline-to-germline maternal transmission 14,15,21,36,[59][60][61][62][63] . wMel cells are present in the germline stem cells of adult females, and over the course of oogenesis, wMel localize via kinesin-mediated transport to the pole plasm-the site of germline formation-at the posterior cortex of the developing oocyte.…”

“…In insects, endosymbionts often achieve vertical transmission by occupying the female ovaries. Endosymbionts are observed in germline stem cells in female hosts where they maintain a tight association with the germline throughout oogenesis, thereby ensuring a germline-to-germline route of vertical transmission through the host matriline 14,15,36,37 . In a more circuitous route, some endosymbionts may also colonize the germline from neighboring somatic cells via cell-to-cell migration through a soma-to-germline route of transmission 4,14,15,38,39 .…”