A coupled expression system for plants was established in this study. The 5’-terminal of T7 RNA poly-merase gene was modified by addition of the coding sequence of nuclear location signal from SV40 large T antigen. Plant expression vector pBBT7 was constructed with the modified T7 RNA polymerase gene under the control of CaMV35S promoter. Another expression vector pBTG contained cassette of gusA controlled by T7 promoter. The two vectors were co-transformed into tobacco via the Agrobecte-rium -mediated method. Results of GUS activity indicated that the co-transformed plant with pBBT7 and pBTG showed a high level of GUS activity. The results demonstrated that the coupled expression system of T7 polymerase and T7 promoter was workable in plants.
