Tetracycline-dependent activation of an upstream promoter reveals transcriptional interference between tandem genes within T-DNA in tomato.

Tomato plants stably expressing the tetR gene were transformed with the beta-glucuronidase (GUS) gene and an le20 antisense construct both under the control of the Triple-Op promoter. Induction of GUS mRNA and le20 antisense RNA in leaves was demonstrated in response to tetracycline. le20 antisense induction was also demonstrated in fruit. Activation of the Triple-Op promoter reduced expression of the downstream hygromycin phosphotransferase II (hptII) gene. Transcriptional interference was therefore observed between tandem genes within T-DNA. Such interference may occur in other T-DNAs, but would not be readily observed without an upstream promoter with controllable activity.