Figure 5.

 Targets for Vein/EGFR and Dpp signaling in the Ubx B enhancer. (A) Sequences of wild-type (B) and mutant enhancers (BC, BC2, BM1, BM2), underneath a sketch laying out the palindromic CRE and the two Mad binding sites (Mad A and Mad B); matches to the CRE or Mad binding site consensus sequences (given at bottom) are indicated with horizontal bars in wild-type and mutant enhancers (for CRE above, for Mad below sequences). (B) Activities of these enhancers in the various ps of the visceral mesoderm; black, wild type; red, 24B.GAL4/UAS.Dpp; blue, 24B.GAL4/UAS.Dras1^V12. Levels of lacZ expression are estimated to be strong, ++, or weak, +; expression trailing into a ps is indicated by (+). Note that BM1 mediates additional expression in the wild type and in response to ectopic Dpp and Dras1^V12, indicating a constitutive repressor binding to the Mad B sequence. (C) Summary of the results detailed in B, implicating the CRE as a response sequence for Ras signaling and Mad A as a response sequence for Dpp signaling (see also text); +, strong and consistent response; (+) disabled and, in the case of Ras, patchy response; − no response.