INDUCTION OF DROSOPHILA EYE DEVELOPMENT BY DECAPENTAPLEGIC

The Drosophila decapentaplegic (dpp) gene, encoding a secreted protein of the transforming growth factor-beta (TGF-beta) superfamily, contro ls proliferation and patterning in diverse tissues, including the eye imaginal disc, Pattern formation in this tissue is initiated at the po sterior edge and moves anteriorly as a wave; the front of this wave is called the morphogenetic furrow (MF). Dpp is required for proliferati on and initiation of pattern formation at the posterior edge of the ey e disc, It has also been suggested that Dpp is the principal mediator of Hedgehog function in driving progression of the MF across the disc. In this paper, ectopic Dpp expression is shown to be sufficient to in duce a duplicated eye disc with normal shape, MF progression, neuronal cluster formation and direction of axon outgrowth, Induction of ectop ic eye development occurs preferentially along the anterior margin of the eye disc. Ectopic Dpp clones situated away from the margins induce neither proliferation nor patterning, The Dpp signalling pathway is s hown to be under tight transcriptional and post-transcriptional contro l within different spatial domains in the developing eye disc. In addi tion, Dpp positively controls its own expression and suppresses wingle ss transcription. In contrast to the wing disc, Dpp does not appear to be the principal mediator of Hedgehog function in the eye.