Fig. 3. Osk accumulation in orb^mel homozygous egg chambers. (A) Western blot analysis was performed on total ovarian protein extracts of similarly aged wild-type and orb^mel flies. The reduction in Osk phosphorylation is presumably a consequence of the reduction in Osk accumulation, as Osk protein has been shown to be required for its own phosphorylation and stabilization (Markussen et al., 1997; Riechmann et al., 2002). (B) Whole-mount antibody staining of orb^mel egg chambers with Stau, and Stau and Osk antibodies.