Fig. 4. Ectopic expression of bcd at the posterior pole induces Sxl expression. Merged images of embryos co-immunostained with anti-ß-galactosidase (red) and anti-Vasa (green) antibodies. (A) Embryo produced by wild-type female mated to male carrying the Sxl-Pe:lacZ reporter transgene. ß-galactosidase is detected in somatic cells but not in pole cells. (B) Embryo produced by bcd-nos3'UTR female mated to male carrying the Sxl-Pe:lacZ reporter transgene. ß-galactosidase is detected in both somatic and pole cells. (C) Embryo produced by bcd-nos3'UTR female mutant for tsl mated to male carrying the Sxl-Pe:lacZ reporter transgene. Expression of the Sxl-Pe:lacZ reporter is no longer detected in pole cells when tsl function is removed. Embryos shown in A-C are judged to be female by the activation of Sxl-Pe in somatic cells.