Bazooka and atypical protein kinase C are required to regulate oocyte differentiation in the Drosophila ovary

The par genes, identified by their role in the establishment of anterior-posterior polarity in the Caenorhabditis elegans zygote, subsequently have been shown to regulate cellular polarity in diverse cell types by means of an evolutionarily conserved protein complex including PAR-3, PAR-6, and atypical protein kinase C (aPKC). The Drosophila homologs of par-1, par-3 (bazooka, baz), par-6 (DmPar-6), and pkc-3 (Drosophila aPKC, DaPKC) each are known to play conserved roles in the generation of cell polarity in the germ line as well as in epithelial and neural precursor cells within the embryo. In light of this functional conservation, we examined the potential role of baz and DaPKC in the regulation of oocyte polarity. Our analyses reveal germ-line autonomous roles for baz and DaPKC in the establishment of initial anterior-posterior polarity within germ-line cysts and maintenance of oocyte cell fate. Germ-line clonal analyses indicate both proteins are essential for two key aspects of oocyte determination: the posterior translocation of oocyte specification factors and the posterior establishment of the microtubule organizing center within the presumptive oocyte. We demonstrate BAZ and DaPKC colocalize to belt-like structures between germarial cyst cells. However, in contrast to their regulatory relationship in the Drosophila and C. elegans embryos, these proteins are not mutually dependent for their germ-line localization, nor is either protein specifically required for PAR-1 localization to the fusome. Therefore, whereas BAZ, DaPKC, and PAR-1 are functionally conserved in establishing oocyte polarity, the regulatory relationships among these genes are not well conserved, indicating these molecules function differently in different cellular contexts.