Fig. 3. Staining for the Wingless (Wg) protein in Drosophila tissues. (A) In wild-type (wt) embryos, Wg staining (green) is diffuse, indicating that the protein is secreted. (B) In embryos carrying the wg^S21 allele, Wg appears to be confined to cells and not secreted. (C) In a porcupine (porc)-mutant embryo, Wg is also confined to producing cells, indicating that it is not secreted. (D,E) Staining for the Wg protein (green) in a wing imaginal disc that contains a clone of cells mutant for porc. The position of the clone is indicated by a lack of staining for ß-galactosidase (red) and is outlined (D). The clone contains cells of the dorsal-ventral wing boundary where Wg is made. In the clone, Wg protein accumulates and is not secreted (arrows). Data provided by Wendy Ching (see also van den Heuvel et al., 1993).