Tumor induction by Agrobacterium tumefaciens: analysis of the boundaries of T-DNA.

Molecular cloning has been used to isolate the ends of that portion of the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens which has been designated T-DNA and which has been transferred to the genome of tobacco crown gall tumor cells. Analysis of the DNA sequences of the plant border clones compared with the corresponding sequences of the Ti plasmid suggests that the mechanism of transferred DNA integration and subsequent stabilization is precise at the right border and imprecise on the left. The T-DNA junction occurs within a variation of a single base pair (bp) on the right but varies over at least 70 bp on the left. In addition, there are several sequences which are repeated near the ends of the T-DNA region in the Ti plasmid. Seemingly, there is no specificity with regard to the site of integration in the plant genome.