EFFICIENCY OF THE TETRACYCLINE-DEPENDENT GENE-EXPRESSION SYSTEM - COMPLETE SUPPRESSION AND EFFICIENT INDUCTION OF THE ROLB PHENOTYPE IN TRANSGENIC PLANTS

We have investigated the use of the tetracycline-dependent gene expression system to regenerate and propagate tobacco plants transformed with a gene whose product - when highly expressed - interferes with regeneration and/or further reproduction. Plants transformed with the Agrobacterium rhizogenes rolB gene under the control of the tetracycline-dependent expression system were phenotypically indistinguishable from wild type owing to efficient repression of the promoter. Induction of the rolB gene with tetracycline led to high-level expression of the rolB mRNA, which resulted in extremely stunted plants with necrotic and wrinkled leaves that did not develop a floral meristem. Upon cessation of tetracycline treatment healthy shoots developed even from severely affected meristems. Data on the dose response of the rolB phenotype as a function of tetracycline concentration demonstrate that the tetracycline-dependent gene expression system can be used to modulate the manifestation of a particular phenotype.