Fig. 1. D-h expression is activated by a Hh-response element. (A) A third instar leg imaginal disc depicting expression of the DV-h stripes (blue) relative to ac expression (green) and the compartment boundary. The D-h and V-h stripes occupy distinct registers relative to the AP boundary. (B) (Top) map of the h locus showing the position of the D-h enhancer. Below is shown a more detailed map of the D-h enhancer. Fragments tested in reporter constructs are shown beneath the detailed map: full-length D-h enhancer (light blue) and the Hh response element (HHRE, dark blue), which has two Ci binding sites and the repression element (REPE, red; see text and Fig. 3). The CMB site in the REPE is described in the text and in Fig. 8. (C) Sequence of two Ci-binding sites present in the HHRE. Underlined bases were altered in the Ci1, Ci2 or Ci1&2 double mutant (see Materials and methods). (D,E) lacZ expression in leg imaginal discs carrying: D-h-lacZ (D) and HHRE-lacZ (E). (F-G) lacZ expression directed by HHRE-lacZ site mutants: Ci1 mutant (F), Ci2 (G) and Ci1&2 (H).