Fig. 1. Dome internalization is dependent on Upd ligand binding. (A) Schematic representation of a stage 8 egg chamber. The gradient of apically located vesicles is represented by red dots. Polar cells are in black. (B,C) Dome is expressed in a gradient (white wedges) of apically located vesicles at the anterior (B) and posterior (C) poles of the egg chamber. The abundance and distribution of Dome vesicles depend on the distance from the polar cells (marked with A101--galactosidase; green), the source of the Upd ligand. (D) When polar cells (arrow; marked with Fas III, membrane marker, green) are wild type for Upd (i.e. nuclear-GFP positive), Dome is present in intracellular vesicles. (E) By contrast, when polar cells (arrow) are mutant for Upd (i.e. nuclear-GFP negative), Dome is not detected in intracellular vesicles. In D and E, polar cells are marked using the FasIII antibody (membrane green staining). The clonal marker is GFP (nuclear green staining). Bars, 10 µm.