Utility of tetracycline-inducible promoter system in transgenic catharanthus roseus hairy roots

Catharanthus roseus can produce several valuable pharmaceuticals, including the anticancer bisindole drugs vinblastine and vincristine, through terpenoid indole alkaloid (TIA) pathways. Overexpression or silencing of some key genes in the TIA pathways in a timely manner through the use of chemical-inducible gene expression systems may result in a favorable metabolic flux toward drug biosyntheses. In this study, transgenic root line Tet3, carrying reporter gene gusA under control of a tetracycline (Tc)-inducible promoter, was used to study this promoter utility in C. roseus transgenic hairy roots. Three days before the stationary growth stage, different Tc concentrations (0.0, 0.1, 1.0, 5.0, and 10.0 mg/L) were applied in root liquid cultures. Both a GUS-staining assay and gusA transcript level quantification showed that induction of the gusA gene was dramatically enhanced by an increase of Tc concentration in the root culture. By 96 h after Tc depletion from the liquid culture, gusA transcript levels had dropped to the level of uninduced roots. However, gusA expression leakage in the root tips, especially at the early exponential-growth stage, limited the inducible-system application in C. roseus hairy roots. © 2009 by The University of Chicago.