A nuclear localization signal and the C-terminal omega sequence in the Agrobacterium tumefaciens VirD2 endonuclease are important for tumor formation.
The T-DNA portion of the Agrobacterium tumefaciens tumor-inducing (Ti) plasmid integrates into plant nuclear DNA. Direct repeats define the T-DNA ends; transfer begins when the VirD2 endonuclease produces a site-specific nick in the right-hand border repeat and attaches to the 5' end of the nicked strand. Subsequent events generate linear single-stranded VirD2-bound DNA molecules that include the entire T-DNA (T-strands). VirD2 protein contains a nuclear localization signal (NLS) near the C terminus and may direct bound T-strands to plant nuclei. We constructed mutations in virD2 and showed that the NLS was important for tumorigenesis, although T-strand production occurred normally in its absence. A tobacco etch virus NLS, substituted for the VirD2 NLS, restored tumor-inducing activity. Amino acids (the omega sequence) at the C terminus of VirD2, outside the NLS and the endonuclease domain, contributed significantly to tumorigenesis, suggesting that VirD2 may serve a third important function in T-DNA transfer.
Shurvinton
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CE
Department of Agricultural Chemistry, Oregon State University, Corvallis 97331-6502.
Hodges
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Ream
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W
D016960:Agrobacterium tumefaciens / Q000235:genetics* / Q000472:pathogenicity; D000595:Amino Acid Sequence; D001120:Arginine / Q000031:analogs & derivatives / Q000235:genetics; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism; D004252:DNA Mutational Analysis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010935:Plant Diseases / Q000235:genetics*; D010957:Plasmids; D016415:Sequence Alignment; D017384:Sequence Deletion
C008666:nopaline; C005394:octopine; D001120:Arginine