Fig. 2: Drosophila dTSSK is crucial for spermiogenesis.

a Sperm nuclear morphology at different stages of spermiogenesis in wild-type (w¹¹¹⁸), dTSSK^−/−, and dTSSK-rescued dTSSK^−/− flies. The right panel at the needle stage shows whole-mount 64-cell spermatids. Scale bar, 10 μm. Spermatid nuclei of dTSSK^−/− flies have a curled, decondensed, and disorganized morphology (orange arrows) in/after the late canoe stage. DNA stained with DAPI, white. Scale bar, 5 μm. b Live imaging showing degeneration of basal body localization (orange arrowhead) in final-stage spermatids of dTSSK^−/− male flies. PACT was used as a marker of the basal body. PACT-GFP fluorescence (green) is detected in spermatid nuclei from the early canoe stage to the final developmental stage in testes of wild-type and dTSSK^−/− flies. Scale bar, 5 μm. c Cytological examination showing defects of flagellar arrangement in dTSSK^−/− male flies. The upper panel shows the morphology of the whole testis in wild-type (w¹¹¹⁸) and dTSSK^−/− flies. The lower panel shows the arrangement of a small patch of flagella (white rectangle) in testicular tissue. d Phalloidin staining of spermatids of w¹¹¹⁸ and TSSK^−/− flies showing the failure of IC formation after dTSSK depletion. ICs stained with phalloidin, red. Nuclei stained with DAPI, blue. Scale bar, 5 μm.