The molecular motor dynein is involved in targeting Swallow and bicoid RNA to the anterior pole of Drosophila oocytes

Localization of bicoid (bcd) messenger RNA to the anterior pole of the Drosophila oocyte requires the exuperantia (exu), swallow (swa) and staufen (stau) genes. We show here that Swa protein transiently co-localizes with bcd RNA in mid-oogenesis. Swa also localizes to the anterior pole of the oocyte in the absence of bcd RNA. This localization does not require Exu, but depends on intact microtubules. In mutant ovaries with duplicated polarity of microtubules, Swa and bcd RNA are ectopically localized at the posterior pole, as well as being present at the anterior pole. We identify dynein light chain-1 (Ddlc-1), a component of the minus-end-directed microtubule motor cytoplasmic dynein, as a Swa-binding protein. We propose that Swa acts as an adaptor for the dynein complex and thereby enables dynein to transport bcd RNA along microtubules to their minus ends at the anterior pole of the oocyte.