The Agrobacterium tumefaciens virulence D2 protein is responsible for precise integration of T-DNA into the plant genome

The VirD2 protein of Agrobacterium tumefaciens was shown to pilot T-DNA during its transfer to the plant cell nucleus. We analyze here its participation in the integration of T-DNA by using a virD2 mutant. This mutation reduces the efficiency of T-DNA transfer, but the efficiency of integration of T-DNA per se is unaffected. Southern and sequence analyses of integration events obtained with the mutated VirD2 protein revealed an aberrant pattern of integration. These results indicate that the wild-type VirD2 protein participates in ligation of the 5'-end of the T-strand to plant DNA and that this ligation step is not rate limiting for T-DNA integration.