Isolation of genes active during hormone-induced morphogenesis in Drosophila imaginal discs.

Mass-isolated Drosophila imaginal discs cultured in vitro undergo morphogenesis (evagination) in response to the insect steroid hormone 20-hydroxyecdysone. In vitro translation of mRNA isolated from evaginating discs shows accumulation of at least five new mRNA transcripts that are present only in membrane-bound polysomal RNA and presumably encode imaginal disc membrane or secreted proteins. Using a modified differential hybridization screen employing a competition step, six different hormone-inducible membrane protein gene sequences were isolated. These genes constitute a new set of 20-hydroxyecdysone responsive loci that may encode gene products specifically required for imaginal disc morphogenesis.