spoonbill, a new Drosophila female-sterile mutation, interferes with chromosome organization and dorsal-ventral patterning of the egg

We have identified a new mutation, spoonbill (spoon), which interferes with two developmental processes during Drosophila oogenesis, nurse cell-nuclei chromatin organization and anterior-dorsal patterning of the eggshell. Here, we describe the localization patterns of key regulators of axis determination and the expression of follicle cell-specific markers involved in eggshell patterning in egg chambers from spoonbill females. Our molecular characterization of the patterning defects associated with the mutation reveals abnormalities in two major signaling pathways, the grk/Egfr and the Dpp/TGF-β, that together control the elaborate patterning of the anterior follicular epithelium. The function of spoonbill appears to be required for dpp transcription in a specialized population of follicle cells and for the selective transport of grk mRNA from the nurse cells into the oocyte, as well as for its proper localization and translation. This finding places the spoonbill gene upstream of both pathways.