Bazooka and PAR-6 are required with PAR-1 for the maintenance of oocyte fate in Drosophila

The anterior-posterior axis of C. elegans is defined by the asymmetric divi sion of the one-cell zygote, and this is controlled by the PAR proteins, in cluding PAR-3 and PAR-B, which form a complex at the anterior of the cell, and PAR-1, which localizes at the posterior [1-4], PAR-1 plays a similar ro le in axis formation in Drosophila: the protein localizes to the posterior of the oocyte and is necessary for the localization of the posterior and ge rmline determinants [5, 6], PAR-1 has recently been shown to have an earlie r function in oogenesis, where it is required for the maintenance of oocyte fate and the posterior localization of oocyte-specific markers [7, 8], Her e, we show that the homologs of PAR-3 (Bazooka) and PAR-B are also required to maintain oocyte fate. Germline clones of mutants in either gene give ri se to egg chambers that develop 16 nurse cells and no oocyte, Furthermore, oocyte-specific factors, such as Orb protein and the centrosomes, still loc alize to one cell but fail to move from the anterior to the posterior corte x. Thus, PAR-1, Bazooka, and PAR-6 are required for the earliest polarity i n the oocyte, providing the first example in Drosophila where the three hom ologs function in the same process. Although these PAR proteins therefore s eem to play a conserved role in early anterior-posterior polarity in C. ele gans and Drosophila, the relationships between them are different, as the l ocalization of PAR-I does not require Bazooka or PAR-6 in Drosophila, as it does in the worm.