Specific expression of the foreign gene regulated by the rice rbcS promoter in transgenic rice

To use different types of promoters intransgenic rice research, the 5'-upstream regula-tion region of rice Rubisco small subunit gene(rbcS) was cloned from a Chinese cultivarWuyunjing 8, and its sequences were confirmedby comparison with the known genome se-quences of both japonica and indica rice. Thecloned rbcS promoter was fused to the 5'-up-stream of GUS (beta-glucuronidase) coding re-gion in a binary vector (Fig.1), and introducedinto rice by Agrogacterium-mediatedtransformation. The integration of the rbcS-GUSfusion gene in transgenic rice was confirmed byPCR analysis (Fig.2). The results of both his-tochemical staining and quantitative analysis ofGUS activity showed that the expression levelof GUS fusion gene was significantly strongerin leaf blade and sheath than in other organs oftransgenic rice plants, and the GUS activity wasrestricted to the mesophyll cells of leaf tissue(Figs.3, 4), which showed that the rice rbcS pro- moter could control not only the tissue- but alsothe cell-specific expression of foreign genes intransgenic rice. The present results also demon-strated that light induction had a significant ef-fect on the enhancement of transgene’s expres-sion when regulated by the rice rbcS promoterin transgenic rice (Fig.5). Our results showed thatthe rice rbcS promoter might be very useful forthe expression of target genes in transgenic rice,with particularly high efficiency in leaf tissues.