Complementary and mutually exclusive activities of decapentaplegic and wingless organize axial patterning during Drosophila leg development.

Growth and patterning of the Drosophila leg are organized by three secreted proteins: Hedgehog (Hh), Wingless (Wg), and Decapentaplegic (Dpp). Hh is secreted by posterior cells; it acts at short range to induce dorsal anterior cells to secrete Dpp and ventral anterior cells to secrete Wg. Here we show that the complementary patterns of dpp and wg expression are maintained by mutual repression: Dpp signaling blocks wg transcription, whereas Wg signaling attenuates dpp transcription. We also show that this mutual repression is essential for normal axial patterning because it ensures that the dorsalizing and ventralizing activities of Dpp and Wg are restricted to opposite sides of the leg primordium and meet only at the center of the primordium to distalize the appendage.