Transducing the Dpp morphogen gradient in the wing of Drosophila: Regulation of Dpp targets by brinker

Dpp, a TGF beta, organizes pattern in the Drosophila wing by acting as a gr aded morphogen, activating different targets above distinct threshold conce ntrations. Like other TGF beta s, Dpp appears to induce transcription direc tly via activation of a SMAD, Mad. However, here we demonstrate that Dpp ca n also control gene expression indirectly by downregulating the expression of the brinker gene, which encodes a putative transcription factor that fun ctions to repress Dpp targets. The medial-to-lateral Dpp gradient along the anterior-posterior axis is complemented by a lateral-to-medial gradient of Drinker, and the presence of these two opposing gradients may function to allow cells to detect small differences in Dpp concentration and respond by activating different target genes.