Creation of ecdysone receptor chimeras in plants for controlled regulationof gene expression

Transformation with a chimeric receptor containing the glucocorticoid trans activation and DNA-binding domains fused to an ecdysteroid receptor-ligand- binding domain permits ecdysone agonist-inducible gene expression in monoco tyledonous plant cells. The inducible system is based on the specific activ ation of a chimeric receptor containing the ligand-binding domain of the He liothis virescens ecdysteroid receptor and the inducer RH5992 (a 20-hydroxy ecdysone agonist). RH5992 is an non-steroidal agrochemical with a high spec ificity for lepidopteran ecdysone receptors. Addition of RH5992 to transfor med cells results in high levels of inducible expression in a ligand-specif ic manner, particularly when the effector receptor is coupled to the strong transactivator VP16. A chimeric construct containing the Drosophila ecdyso ne ligand-binding domain failed to activate reporter gene activity with RH5 992, while activation was observed in the presence of muristeroneA. The sys tem described provides the basis for an inducible gene expression system th at is compatible with agricultural use.