Figure 10.

Summary of regulatory interactions among hth, Dll, cut, and ss. On the left are shown proximo-distal expression patterns in the late second instar, shortly after Dll and ss (B6.9) have become activated in the antennal disc and when hth expression is diminished distally. At this time, ss is activated by both hth and Dll. In the third instar (right), the ss antennal enhancer continues to be activated by Dll, but no longer requires hth for its expression. Instead, ss weakly represses hth, resulting in its down-regulation in A3. Repression by cut defines the proximal limit of ss expression during the third instar; regulatory interactions between cut and ss during the second instar have not been examined.