Production of gurken in the nurse cells is sufficient for axis determination in the Drosophila oocyte.

The asymmetric localization of gurken mRNA and protein in the developing Drosophila oocyte defines both the anteroposterior and dorsoventral axes of the future embryo. Understanding the origin of these asymmetries requires knowledge of the source of gurken transcripts. During oogenesis most transcripts in the oocyte are produced by the associated nurse cells, but it has been proposed that gurken is an exceptional oocyte-derived transcript. Using a novel application of a standard mitotic recombination technique, we generated mosaic egg chambers in which the nurse cells, but not the oocyte, could produce gurken. Gurken was properly localized in these mosaics and oocyte axial polarity was established normally, indicating that the nurse cells synthesize gurken and that their contribution is sufficient for Gurken function. Our data demonstrate the existence of a mechanism for transport of gurken from the nurse cells and its subsequent localization within the oocyte.