Fig. 5: Dfd–Exd activates AP2x-377 via binding sites in domain 3.

a Schematic representation of mutations inserted in domains 2 and 3 of AP2x-377 to disrupt the Dfd–Exd binding sites (indicated by an asterisk) identified by EMSAs. Transgenes were generated to express GAL4 under the control of the different mutated AP2x-377 enhancers. b The activity of the mutated AP2x-377 enhancers was determined by crossing flies carrying the different GAL4 transgenes with UAS-LacZ flies. c–e” AP2x-377 > LacZ (c–c”), AP2x-377-D2mt > LacZ (d–d”) and AP2x-377-D3mt > LacZ (e–e”) stage 14 embryos were collected and stained for β−galactosidase (green in c, d, e, grey in c’, d’, e’) to determine the activity of the different enhancers in the maxillary segment. Dfd staining labels the maxillary segment (red in c, d, e, grey in c”, d” and e”). f Quantification of AP2x-377 (n = 8) and AP2x-377-D2mt (n = 7) enhancer activity in the posterior border cells of the maxillary segment; n: number of embryos analysed. The activity was determined by measuring the β−galactosidase/Dfd fluorescence ratio in the posterior-ventral border cells of the maxillary segment. The plotted values indicate the mean and the corresponding standard error of the mean of the activity of each enhancer. Statistical relevance was tested with the one-way ANOVA test. ns: non-significant. g–i Analysis of the ventral cirri in 1st instar AP-2¹⁵ homozygous larvae cuticles expressing AP-2 under the control of AP2x-377-GAL4 (g), AP2x-377-D2mt-GAL4 (h) and AP2x-377-D3mt-GAL4 (i). dCi dorsal cirri, vCi ventral cirri. Source files are provided in “Source-Data-File_values”.