Fig. 5. Localization of Snky-GFP during spermatogenesis. The diagram depicts stages of spermatogenesis in which Snky-GFP expression was observed. Letters correspond to confocal images below (A-E). Primary spermatocytes (A) undergo two meiotic divisions to yield round spermatids (B). Differentiation follows (C-E), as spermatids undergo gradual condensation of nuclei (red), elongation of mitochondrial derivatives (blue) and sperm tails (black lines). Individualized, mature sperm are released from the base of the testis into the seminal vesicle (F). Confocal images show stages of spermatogenesis in males that were homozygous for snky¹ and carried two copies of a transgene expressing Snky-GFP (green). Nuclei were visualized by DAPI-staining (red). In A-C, mitochondrial structures were detected with the dye MT-CMXRos (blue). (A) In primary spermatocytes, Snky-GFP and the mitochondrial dye give diffuse cytoplasmic signals. (B) In post-meiotic spermatids at the onion stage, clusters of Snky-GFP-containing spheres are adjacent to nuclei and mitochondrial derivatives. (C) Snky-GFP is visible in clusters of spheres along the length of elongating spermatids, but a prominent spot (arrow) is associated with each nucleus. (D) A single slightly oval Snky-GFP signal is associated with each spermatid nucleus as nuclear condensation begins. (E) In cysts of late spermatids, Snky-GFP appears as a thin oval signal distal to the needle-shaped sperm nucleus. (F) Individualized sperm present in the seminal vesicle contain Snky-GFP signal located at the apical tip and consistent with localization to the acrosome. Scale bars: 10 µm.