A novel homeobox gene mediates the Dpp signal to establish functional specificity within target cells.

Morphogen gradients of secreted molecules play critical roles in the establishment of the spatial pattern of gene expression. During midgut development in Drosophila, secreted molecules of Decapentaplegic (Dpp) and Wingless (Wg) establish unique transcriptional regulation within target cells to specify the resultant cell types. Here we report the identification of a novel homeobox gene, defective proventriculus (dve), which is required for the midgut specification under the control of Dpp and Wg. In dve mutants, two distinct parts of the midgut, the proventriculus and middle midgut, are abnormally organized. The Wg signal regulates dve expression during proventriculus development. On the other hand, dve is a downstream target of Dpp in the middle midgut and defines the functional specificity of copper cells along with another Dpp target gene, labial. Thus, the dve gene acts under the two distinct extracellular signals at distant parts of the midgut primordia.