An estrogen receptor-based transactivator XVE mediates highly inducible gene expression in transgenic plants

We have developed an estrogen receptor-based chemical-inducible system for use in transgenic plants. A chimeric transcription activator, XVE, was asse mbled by fusion of the DNA-binding domain of the bacterial repressor LexA ( X), the acidic transactivating domain of VP16 (V) and the regulatory region of the human estrogen receptor (E; ER). The transactivating activity of th e chimeric XVE factor, whose expression was controlled by the strong consti tutive promoter G10-90, was strictly regulated by estrogens. In transgenic Arabidopsis and tobacco plants, estradiol-activated XVE can stimulate expre ssion of a GFP reporter gene controlled by the target promoter, which consi sts of eight copies of the LexA operator fused upstream of the -46 35S mini mal promoter. Upon induction by estradiol, GFP expression levels can be eig htfold higher than that transcribed from a 35S promoter, whereas the unindu ced controls have no detectable GFP transcripts, as monitored by Northern b lot analysis. Neither toxic nor adverse physiological effects of the XVE sy stem have been observed in transgenic Arabidopsis plants under all the cond itions tested. The XVE system thus appears to be a reliable and efficient c hemical-inducible system for regulating transgene expression in plants.