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EMBO J. 1986 Jun;5(6):1137-42.

Overdrive, a T-DNA transmission enhancer on the A. tumefaciens tumour-inducing plasmid.

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Institute for Molecular Biology, Department of Biology, Indiana University, Bloomington, IN 47405, USA.


During crown gall tumorigenesis a specific segment of the Agrobacterium tumefaciens tumour-inducing (Ti) plasmid, the T-DNA, integrates into plant nuclear DNA. Similar 23-bp direct repeats at each end of the T region signal T-DNA borders, and T-DNA transmission (transfer and integration) requires the right-hand direct repeat. A chemically synthesized right border repeat in its wild-type orientation promotes T-DNA transmission at a low frequency; Ti plasmid sequences which normally flank the right repeat greatly stimulate the process. To identify flanking sequences required for full right border activity, we tested the activity of a border repeat surrounded by different amounts of normal flanking sequences. Efficient T-DNA transmission required a conserved sequence (5' TAAPuTPy-CTGTPuT-TGTTTGTTTG 3') which lies to the right of the two known right border repeats. In either orientation, a synthetic oligonucleotide containing this conserved sequence greatly stimulated the activity of a right border repeat, and a deletion removing 15 bp from the right end of this sequence destroyed it stimulatory effect. Thus, wild-type T-DNA transmission required both the 23-bp right border repeat and a conserved flanking sequence which we call overdrive.

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