Agrobacterium tumefaciens transfers DNA from its Ti plasmid to plant host cells. The genes located within the transferred DNA of Ti plasmid including the octopine synthase gene (OCS) are expressed in plant host cells. The 3′-flanking region of OCS gene, known as OCS terminator, is widely used as a transcriptional terminator of the transgenes in plant expression vectors. In this study, we found the reversed OCS terminator (3′-OCS-r) could drive expression of hygromycin phosphotransferase II gene (hpt II) and beta-glucuronidase gene in Escherichia coli, and expression of hpt II in A. tumefaciens. Furthermore, reverse transcription-polymerase chain reaction analysis revealed that an open reading frame (ORF12) that is located downstream to the 3′-OCS-r was transcribed in A. tumefaciens, which overlaps in reverse with the coding region of the OCS gene in octopine Ti plasmid.
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We would like to thank an anonymous reviewer for her/his critical and constructive comments that led to the improvement of this article. We thank Dr. Stephen C. Winans (Cornell University, USA) for the A. tumefaciens strains of A348 and R10, and Dr. Peter M. Waterhouse (CSIRO Plant Industry, Australia) for the pHANNIBAL and pART27 plasmids. This work was supported by the National Natural Science Foundation of China (grant nos. 30570943 and 30771111), and the Knowledge Innovation Program of the Chinese Academy of Sciences (grant no. KSCX2-YW-Z-0723) to Z.-F. Xu.
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