MAD ACTS DOWNSTREAM OF DPP RECEPTORS, REVEALING A DIFFERENTIAL REQUIREMENT FOR DPP SIGNALING IN INITIATION AND PROPAGATION OF MORPHOGENESISIN THE DROSOPHILA EYE

Decapentaplegic (Dpp), a member of the TGF-beta family of cytokines, h as been implicated in many patterning processes in Drosophila, includi ng the initial steps of pattern formation in the developing eye. We sh ow that the Mothers against dpp (Mad) gene is required for dpp signali ng during eye development. Clonal analysis demonstrates a cell-autonom ous function for Mad and genetic interactions indicate that Mad is an essential component of the signal transduction pathway downstream of t he Dpp receptors in responding cells. Mad-mediated dpp signaling is ab solutely required for the initiation of the morphogenetic furrow in th e eye, but has only a minor role in its subsequent propagation across the eye disc. We also present evidence for the repression of wingless transcription by dpp signaling.