The T-DNA-linked VirD2 protein contains two distinct functional nuclear localization signals

Agrobacterium tumefaciens causes neoplastic growth in plants by transferring a piece of DNA, called T-DNA, into the nucleus of the plant cell. The virulence protein VirD2 of A. tumefaciens is tightly linked to the T-DNA and is thought to direct it to the plant genome. Here we show that the VirD2 protein contains two nuclear localization signals that are functional both in yeast and in plant cells. One signal is located in the N-terminal part of the protein and resembles a single-cluster-type nuclear localization signal. The second signal is near the C terminus and is a bipartite-type nuclear localization signal. The involvement of these sequences in the entry of the T-DNA into the nucleus is discussed.