Ecdysone agonist inducible transcription in transgenic tobacco plants

A novel chemical-induced gene regulatory system for plants consisting of tw o molecular components is described. The first, or regulatory, cassette com prises a chimeric receptor composed of the hinge and ligand binding domains of the Heliothis virescens ecdysone receptor and the transactivation domai n of the Herpes simplex VP16 protein fused to the DNA binding domain and tr ansactivation of a mammalian glucocorticoid receptor. The second component, a reporter cassette, contains six copies of the glucocorticoid response el ement (GRE) fused to the minimal 35SCaMV promoter and P-glucuronidase. The system uses a commercially available non-steroidal ecdysone agonist, RH5992 (tebufenozide), as an inducer. Activation of gene expression is shown in b oth tobacco transient protoplasts and transgenic plants. The response is li gand dependent and is modulated by the change in minimal promoter context. The system is capable of inducing transgene activity up to 420-fold corresp onding to 150% of the activity observed with positive controls (35SCaMV:GUS ).