a–f, f′, Ovaries showing nuclear-stain DAPI in blue and Blochmannia in white: germline stem-cell niche without Blochmannia (a), germarium in which Blochmannia colonization occurs (b), Blochmannia initially fill the entirety of the cytoplasm of young oocytes (c) and progressively localize to the posterior pole of older oocytes (d–f), where Blochmannia surrounds the germplasm (f′). f′, g–i, Mature oocytes showing maternal expression of germline genes in oocytes, showing osk mRNA in magenta (f′), Vas protein in yellow (g), nos mRNA in blue (h), Aub protein in green (i) and nuclear-stain DAPI in blue. j–o, Subcellular localization zones in stage (st)-1 freshly laid eggs showing Aub protein in green (j), Gcl protein in orange (k), Tud protein in white (l), Hsp90 protein in red (m), smg mRNA in blue (n) and stau mRNA in blue (o). p–u, Expression in stage-6 cellular blastoderm embryos showing Aub protein in green (p), Gcl protein in orange (q), Tud protein in white (r), Hsp90 protein in red (s), smg mRNA in blue (t) and stau mRNA in blue (u). Arrowheads indicate subcellular localization or expression zones of germline genes: zone 1, zone 1a, zone 1b, zone 2, zone 3 and zone 4. Anterior is to the left, dorsal is to the top. In situ hybridization and immunohistochemistry experiments were repeated at least 8 times independently on n ≥ 30 oocytes or embryos per developmental stage.