TRANSIENT POSTERIOR LOCALIZATION OF A KINESIN FUSION PROTEIN REFLECTSANTEROPOSTERIOR POLARITY OF THE DROSOPHILA OOCYTE

Background: During oogenesis in Drosophila, determinants that will dic tate abdomen and germline formation are localized to the 'polar plasm' in the posterior of the oocyte. Assembly of the polar plasm involves the sequential localization of several messenger RNAs and proteins to the posterior of the oocyte, beginning with the localization of oskar mRNA and Staufen protein during stages 8 and 9 of oogenesis. The mecha nism by which these two early components accumulate at the posterior i s not known. We have investigated whether directed transport along mic rotubules could be used to accomplish this localization. Results: We h ave made a fusion protein composed of the bacterial beta-galactosidase enzyme as a reporter, joined to part of the plus-end-directed microtu bule motor, kinesin, and have found that the fusion protein transientl y localizes to the posterior of the oocyte during stages 8 and 9 of oo genesis. Treatment with the microtubule-depolymerizing agent colchicin e prevents both the localization of the fusion protein and the posteri or transport of oskar mRNA and Staufen protein. Furthermore, the fusio n protein localizes normally in oocytes mutant for either oskar and st aufen, but not in other mutants in which oskar mRNA and Staufen protei n are mislocalized. Conclusions: Association with a plus-end-directed microtubule motor can promote posterior localization of a reporter pro tein during oogenesis. The genetic requirements for this localization and its sensitivity to colchicine, both of which are shared with the p osterior transport of oskar mRNA and Staufen protein, suggest that sim ilar mechanisms may function in both processes.