Fig. 6. Polo overexpression restores BicD^PA66 protein function during early oogenesis. (A,B) C(3)G is in red and BicD in green. (A) BicD^PA66 ovariole with no cell in meiosis from stage 2b of the germarium, and diffuse localization of BicD. (B) BicD^PA66 ovariole overexpressing Polo. Each follicle contains an oocyte in meiosis, which accumulates BicD. (C) DNA staining of later stage follicles in a BicD^PA66 ovariole overexpressing Polo. Stage 4 and stage 6 follicles contain an oocyte marked by the presence of the condensed DNA (arrowheads). The follicle at stage 9 is degenerating. (D) Model of a positive feedback loop between Polo and BicD proteins during meiosis restriction and oocyte differentiation. The Polo kinase is required to trigger meiosis and to activate BicD-dependent transport. In turn, BicD is required for the transport of oocyte determinants and for Polo localization.