Fig. 4. The linked Dl- and Zld-binding sites in the 0.68-kb enhancer are required for its VM enhancer activity. Wild type and mutant versions of the 0.68-kb enhancer were used to generate lacZ transformation constructs. Cloning of the transformation constructs, germline transformation, and in situ hybridization were performed as in Fig. 1. Lateral (A, C, E, G, and I, stage 5) and ventral (B, D, F, H, and J, stage 10) views of the embryos are shown; the anterior side is on the left. The 0.68-kb minimal enhancer contains five Dl-binding and three Zld-binding sites. Of these, the Dl3-Zld1 and Dl5-Zld3 sites are closely linked. Intriguingly, Zld1 and Zld3 coincide with two Sna-binding sites to form two modules, each of which is composed of a combination of Dl-, Zld-, and Sna-binding sites.