Synchronous binucleation of Drosophila male accessory gland cells occurs in the pupal stage. (A) Adult accessory gland epithelium labeled as indicated at the bottom left. Main cells (nuclei stained both green and magenta) and secondary cells (nuclei stained only magenta) are shown. The inset at the bottom right depicts an adult male abdomen (gray) and the reproductive systems around the hindgut. Posterior is to the right. Scale bar, 10 μm. (B and C) Synchronous entry into M phase in secondary (B) and main (C) cells in the accessory glands during mid-pupal binucleation stages. Labels as indicated at the bottom right. Scale bars, 50 μm. (D) Schematic diagram showing cell cycle transition of epithelial cells in accessory gland during the pupal stage.