Integration of complete transferred DNA units is dependent on the activity of virulence E2 protein of Agrobacterium tumefaciens.
Agrobacterium tumefaciens transfers transferred DNA (T-DNA), a single-stranded segment of its tumor-inducing (Ti) plasmid, to the plant cell nucleus. The Ti-plasmid-encoded virulence E2 (VirE2) protein expressed in the bacterium has single-stranded DNA (ssDNA)-binding properties and has been reported to act in the plant cell. This protein is thought to exert its influence on transfer efficiency by coating and accompanying the single-stranded T-DNA (ss-T-DNA) to the plant cell genome. Here, we analyze different putative roles of the VirE2 protein in the plant cell. In the absence of VirE2 protein, mainly truncated versions of the T-DNA are integrated. We infer that VirE2 protects the ss-T-DNA against nucleolytic attack during the transfer process and that it is interacting with the ss-T-DNA on its way to the plant cell nucleus. Furthermore, the VirE2 protein was found not to be involved in directing the ss-T-DNA to the plant cell nucleus in a manner dependent on a nuclear localization signal, a function which is carried by the NLS of VirD2. In addition, the efficiency of T-DNA integration into the plant genome was found to be VirE2 independent. We conclude that the VirE2 protein of A. tumefaciens is required to preserve the integrity of the T-DNA but does not contribute to the efficiency of the integration step per se.
Rossi
L
L
Friedrich Miescher-Institut, Basel, Switzerland.
Hohn
B
B
Tinland
B
B
D016960:Agrobacterium tumefaciens / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004269:DNA, Bacterial / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000378:metabolism; D007473:Ion Channels; D008969:Molecular Sequence Data; D010957:Plasmids; D011995:Recombination, Genetic
D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D007473:Ion Channels; C051583:virE2 protein, Agrobacterium; D003851:Deoxyribonucleases