Fig. 7. Proximal, medial and distal domains antagonize one another in the leg, but not in the antenna. Schematics of the leg and the antenna with Hth-expressing domains indicated in blue, Dac-expressing domains in red, and Dll-expressing domains in green. Mutually antagonistic interactions between proximal and medial and between medial and distal maintain domain identity in the leg. By contrast, the same genes do not antagonize the expression of one another in the antenna. This results in the overlapping expression of hth, Dll and dac, and the absence of a functional medial domain defined by dac. Our data are consistent with Dll and Hth repressing leg-specific expression of dac in the antenna and with both Dll and Hth being required for the normal antennal expression of dac in a3.