Fig. 5. CrebA mutations affect secretory activity in the salivary gland. (A,B) Stage 15 and 17 wild-type (CrebA/+) and CrebA mutant embryos were stained with -PH4SG1 (red) and -En PAb (green). (A) At stage 15, Engrailed-positive secretory granules can be detected in CrebA/+, while very few were seen in CrebA mutant salivary glands (arrows). (B) Significantly more secretory granules were detected in stage 17 CrebA/+ salivary glands than in the stage 17 CrebA mutant salivary glands (arrows and arrowheads). The amount of lumenal content increases significantly from stage 15 to 17 in both CrebA/+ and CrebA salivary glands, but is not different in the wild-type versus CrebA mutant glands. (C) Stage 17 sec13 and sec23 salivary glands appear relatively normal with respect to secretory granule levels. The abnormal salivary gland shape in the sec13 mutants is probably linked to other patterning defects observed when this P-element insertion is homozygous. Arrows indicate punctate staining near the apical surface. Arrowheads indicate larger vesiclar staining throughout the cell.