FIG. 2.

In vivo functional analysis of the dpp visceral mesoderm enhancer, dppVM. (A) Map of the dpp locus. The dpp transcription unit is depicted as boxes; protein-coding sequence is black. Arrows indicate promoters. Two enhancers of the dpp gene, the imaginal disc enhancer dppD and the visceral mesoderm enhancer dppVM, are shown in gray. (B–I) Whole mount transgenic Drosophila embryos in which lacZ reporter gene expression is detected by RNA in situ hybridization. Anterior is to the left. Black bars indicate known or predicted protein binding sites, gray indicates wild-type uncharacterized sequence, dashed lines indicate deleted sequence, and white (with a black border) indicates sequence that has been altered but not deleted. (B) Embryos carrying the wild-type, 419-bp dppVM in the Ganesh-Z1 vector,³⁰ driving lacZ expression in visceral mesoderm in parasegment 7. Left, lateral view; right, dorsal view; bottom; diagram of enhancer and reporter gene. (C–G) Lateral views of embryos carrying mutant versions of dppVM (Δ1 through Δ5), in which uncharacterized enhancer regions 1 through 5 are deleted, one at a time. No single deletion abolishes enhancer activity. (H) Dorsal view of embryo carrying a “synthetic” 287-bp version of dppVM, in which the functionally significant Ubx, TCF, and Exd sites are placed together, and all other enhancer sequences are deleted. (I) Dorsal view of embryo carrying construct m12345, in which the TF sites are present in their normal arrangement and spacing, and the sequence of regions 1 through 5 is altered.