The Drosophila Broad-Complex plays a key role in controlling ecdysone-regulated gene expression at the onset of metamorphosis

• DOI: 10.1242/dev.118.3.977
• Publication Date: 2021-04-26T01:22:50Z
• Authors: Felix D. Karim; Gregory M. Guild; Carl S. Thummel
• Keywords: Polytene chromosome; Ecdysone receptor

ABSTRACT During Drosophila third instar larval development, one or more pulses of the steroid hormone ecdysone activate three temporally distinct sets genes in salivary glands, represented by puffs polytene chromosomes. The intermolt are induced first, midthird larvae; these encode a protein glue used animal to adhere itself solid substrate for metamorphosis. repressed at puparium formation as high titer pulse directly induces small set early regulatory genes. both repress their own expression and than 100 late secondary-response Broad-Complex (BR-C) is an ecdysone-inducible gene that encodes family DNA binding proteins defined least lethal complementation groups: br, rbp, l(1)2Bc. We have found BR-C critical appropriate regulation all classes Both rbp l(1)2Bc required induction mid-third larvae. In addition, function repression prepupae; mutants re-induced prepupal pulse, recapitulating response inappropriate stage development. also complete some mRNAs (E74A, E75A, BR-C) efficient most prepupae. Like genes, absolutely dependent on induction. An effect mutations activity can be detected, but likely secondary consequence submaximal ecdysone-induction subset products. Our results indicate plays key role dictating stage-specificity response. ecdysone-receptor complex alone not sufficient primary-response requires prior proteins. These studies define regulator onset metamorphosis Drosophila.