Transcriptional activation of the Drosophila ecdysone receptor by insect and plant ecdysteroids

A number of insect ecdysteroids, plant ecdysteroids and juvenoids were assa yed for their ability to activate Drosophila nuclear receptors in transfect ed tissue culture cells. Discrete modifications to 20-hydroxyecdysone, the apparent natural ligand for the ecdysone receptor (EcR), conferred dramatic changes on the transcriptional activity of this receptor, suggesting that other biologically relevant EcR ligands may exist. Conversely, none of the compounds tested had a significant effect on the activity of three Drosophi la. orphan nuclear receptors: DHR38, DHR78 or DHR96. Taken together, these results demonstrate the selectivity of EcR for a series of natural and synt hetic ecdysone agonists and suggest that as yet untested compounds may be r esponsible for activating DHR38, DHR78 and DHR96. (C) 2000 Elsevier Science Ltd. All rights reserved.