Fig. 1.

Drosophila Sage is expressed and required in the embryonic salivary gland. (A,B) In situ hybridization of sage mRNA (A) and immunostaining with guinea pig antiserum directed against Sage protein (B) reveal similar patterns in stage 10-16/17 Drosophila embryos. (C) Crb apical staining in stage 11-13 sage mutant salivary glands (SGs) was relatively normal. By embryonic stage 15, Crb staining was not detected in the distal half of the SGs of sage mutants, and by stage 17 Crb was not detected in secretory cells (large arrows), although staining appeared normal in the salivary duct (small arrows). wt, wild type. (D) Fkh nuclear staining was relatively normal in stage 12 and declined in intensity by stage 13. Fkh was detected in far fewer SG cells in stage 15 sage mutants than in heterozygous age-matched siblings (arrows). (E) CrebA nuclear staining was relatively normal in stage 13 sage mutant SGs. Very low CrebA levels were detected at stage 15 and staining was not detectable in SGs by stage 16.