Brinker is a target of Dpp in Drosophila that negatively regulates Dpp-dependent genes

Growth and patterning of the Drosophila wing is controlled in part by the l ong-range organizing activities of the Decapentaplegic protein (Dpp)(1-4). Dpp is synthesized by cells that line the anterior side of the anterior/pos terior compartment border of the wing imaginal disc. From this source, Dpp is thought to generate a concentration gradient that patterns both anterior and posterior compartments. Among the gene targets that it regulates are o ptomotor blind (omb)(5), spalt (sal)(6), and daughters against dpp (dad)(7) . We report here the molecular cloning of brinker (brk), and show that brk expression is repressed by npp. brk encodes, a protein that negatively regu lates Dpp-dependent genes. Expression of brk in Xenopus embryos indicates t hat brk can also repress the targets of a vertebrate homologue of Dpp, bone morphogenetic protein 4 (BMP-4). The evolutionary conservation of Brk func tion underscores the importance of its negative role in proportioning Dpp a ctivity.