Fig. 5. Alcian Blue-staining in the embryonic salivary gland requires the activity of genes involved in biological sulfation. (A) Mutations affecting papss were identified by their increased sensitivity to the lethal effects of sodium chlorate. Concentrations of sodium chlorate are shown at top, as are the parental genotypes. At 25 mM and 30 mM sodium chlorate, few papss/+ pupae are present on the sides of the vials. (B-D) Embryos stained with Alcian Blue. Although papss²/+ embryos stain with Alcian Blue (B), embryos homozygous for papss² lack Alcian Blue salivary gland staining (C), as do embryos homozygous for sll^7E18 (D). (E-G) Staining of embryonic salivary glands with an antibody against Windbeutel. The salivary glands of an embryo heterozygous for papss² stain for Windbeutel (E), as do the salivary glands of papss² (F) and sll^7E18 (G) mutant embryos.