Fig. 5. Wg acts upstream of Ss and independently of it in transforming maxillary identity to antennal. (A₁-A₄) Light-microscope images of adult maxillary palps. (A₁) Wild-type maxillary palps with their bordering row of bristles. (A₂) ss^- null homozygote shows strongly reduced maxillary palps. (A₃) wg^gof; ss^- double mutants (shifted to 18°C at 5 days AEL) generally have an enlarged structure, unlike either wg^gof neo-antennae or ss^- stubs. These structures are positioned higher on the head, like neo-antennae (as seen in Fig. 3B). (A₄) Same genotype as in A₃, but with the maxillary palp replaced by distal leg with its distinctive claws. (B-E) Dan (green) and Dfd (red) expression in L3 E-A of (B) a wild-type antennal disc, (C) a wg^gof-induced transformation (ptc-GAL4>UAS-wg^ts shifted to 18°C at 5 days AEL), (D) a ss^gof-induced transformation (ptc-Gal4>UAS-ss), (E) a wg^gof; ss^- disc (shifted to 18°C at 5 days AEL) where Dfd (red) is excluded from the maxillary territory (arrowhead). (F,F') In ss^gof discs harbouring large pygo^- clones (no GFP), Dan (red) is expressed in a narrow band of maxillary cells (F, arrowhead) and Dfd expression (red) is maintained (F', arrowhead). (G) Schematic summary of results. Antennal discs are oriented with posterior towards the right and dorsal towards the bottom; a and mx indicate antenna and maxillary primordia, respectively.