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 tha t 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 w hich bicoid mRNA accumulates normally at the anterior, but oskar mRNA is re directed to the center of the oocyte, resulting in embryonic patterning def ects. These phenotypes arise from a disorganization of the oocyte microtubu le cytoskeleton, consistent with reports that mammalian PAR-1 homologs regu late microtubule dynamics. Thus, Drosophila PAR-1 may remodel the oocyte mi crotubule network to define the posterior as the site for oskar localizatio n. These results identify a molecular parallel between anterior-posterior p olarization in Drosophila and C. elegans.