The Drosophila Homolog of C. elegans PAR-1 Organizes the Oocyte Cytoskeleton and Directs oskar mRNA Localization to the Posterior Pole

In C. elegans, the PAR-1 kinase is localized to the posterior of the zygote and is required for anterior–posterior axis formation. Here, we report that a Drosophila PAR-1 homolog localizes to the posterior of the oocyte with oskar mRNA. Furthermore, par-1 mutants show a novel polarity phenotype in which bicoid mRNA accumulates normally at the anterior, but oskar mRNA is redirected to the center of the oocyte, resulting in embryonic patterning defects. These phenotypes arise from a disorganization of the oocyte microtubule cytoskeleton, consistent with reports that mammalian PAR-1 homologs regulate microtubule dynamics. Thus, Drosophila PAR-1 may remodel the oocyte microtubule network to define the posterior as the site for oskar localization. These results identify a molecular parallel between anterior–posterior polarization in Drosophila and C. elegans.