Post-transcriptional regulation of gurken by encore is required for axis determination in Drosophila

Establishment of anterior-posterior and dorsal-ventral polarity within the Drosophila egg chamber requires signaling between the germline and the somatic cells of the ovary. The gene gurken (grk) encodes a TGFalpha-like protein that is localized within the developing oocyte and is thought to locally activate torpedo/Egfr (top/Egfr), the Drosophila homolog of the EGF receptor, which is expressed throughout the follicular epithelium surrounding the oocyte. grk-Egfr signaling is required early in oogenesis for specification of posterior follicle cell fate and later in oogenesis for dorsal follicle cell fate determination, thus establishing the axes of the egg shell and embryo. Previous studies have shown that these patterning processes are highly sensitive to changes in the levels and localization of grk mRNA. Here we show that post-transcriptional regulation of Grk protein levels is required for correct pattern formation. encore (enc), a gene that functions in the regulation of germline mitosis and maintenance of oocyte identity, is also required for the accumulation of Grk protein during oogenesis. We present evidence that enc regulates Grk post-transcriptionally to ensure adequate levels of signaling for establishment of the anterior-posterior and dorsal-ventral axes.