Polarization of both major body axes in Drosophila by gurken-torpedo signalling.

Anterior-posterior polarity in Drosophila arises from the movement of the oocyte to the posterior of the egg chamber, and the subsequent acquisition of posterior fate by the adjacent somatic follicle cells. We demonstrate that gurken is necessary in the oocyte and torpedo/DER in the follicle cells for the induction of posterior fate. As the gurken-torpedo/DER pathway also establishes dorsoventral polarity later in oogenesis, Drosophila uses the same germline to soma signalling pathway to determine both embryonic axes.