Fig. 2. Long Osk, but not Short Osk, can anchor at the posterior pole of the oocyte. (A-E) Confocal images of Osk isoforms detected by immunostaining of osk RNA-null ovaries osk^A87/Df(3R)p-XT103, expressing either a wild-type osk transgene (upper panels), oskM1R encoding Short Osk (middle panels) or oskM139L encoding Long Osk (lower panels). The rabbit anti-Osk polyclonal serum used in these experiments detects both Osk isoforms. During late stage 10, Long Osk remains tightly anchored at the posterior pole in a crescent-shaped pattern (bottom panels), as observed when both isoforms are expressed (top panels). At the same stage, Short Osk shows either a ‘dotty’ localization close to the posterior cortex (3%) or is strongly detached in aggregated particles that disperse in the bulk ooplasm (97%) (middle panels). (B) Magnification of the posterior tip of the oldest egg chamber shown in A. (C-E) Co-localization of pole plasm components at the posterior tip of stage 10 egg chambers. (C) Merged confocal images of osk mRNA (green) and Osk protein (red) simultaneously detected by in situ hybridization and antibody staining. Merged confocal images of immunohistochemically detected Staufen (red) and Osk (green) (D), and of Oskar (green) and Vasa (red) (E).