γ-Tubulin37C and γ-tubulin ring complex protein 75 Are Essential for bicoid RNA Localization during Drosophila Oogenesis

Abstract bicoid ( bcd ) RNA localization requires the activity of exuperantia and swallow at sequential steps of oogenesis and is microtubule dependent. In a genetic screen, we identified two novel genes essential for bcd RNA localization. They encode maternal γ-Tubulin37C ( γTub37C ) and γ-tubulin ring complex protein 75 ( Dgrip75 ), both of which are γ-tubulin ring complex components. Mutations in these genes specifically affect bcd RNA localization, whereas other microtubule-dependent processes during oogenesis are not impaired. This provides direct evidence that a subset of microtubules organized by the γ-tubulin ring complex is essential for localization of bcd RNA. At stage 10b, we find γTub37C and Dgrip75 anteriorly concentrated and propose the formation of a microtubule-organizing center at the anterior pole of the oocyte.