Disease relevance of virD2

• Virulence genes virD1 and virD2 are required for T-DNA processing in Agrobacterium tumefaciens [1].
• We have constructed a chimeric gene by fusing the virD2 gene and the Escherichia coli lacZ gene [2].
• With an endonuclease from Streptomyces albus G the DNA was digested to 19 fragments, with molecular weights ranging from 600 to 7,400 daltons [3].

High impact information on virD2

• We report here that the virD operon encodes a site-specific endonuclease that cleaves at a unique site within each of the 24 bp direct repeats that flank the T-DNA [4].
• Agrolistically transformed tobacco calli were obtained after codelivery of virD1 and virD2 genes together with a selectable marker flanked by border sequences [5].
• The virulence genes virD1 and virD2 from Agrobacterium tumefaciens that are required in bacteria for excision of T-strands from the tumor-inducing plasmid were placed under the control of the CaMV35S promoter and codelivered with a target plasmid containing border sequences flanking the gene of interest [5].
• DNA modifying enzymes of Agrobacterium tumefaciens: effect of DNA topoisomerase, restriction endonuclease, and unique DNA endonuclease on plasmid and plant DNA [6].
• To the left of cagII in this cosmid were genes for homologues of HsIU (heat-shock protein) and Era (essential GTPase); to the right of cagII were homologues of genes for a type I restriction endonuclease and ion transport functions [7].

Chemical compound and disease context of virD2

• Mutational analysis of Agrobacterium tumefaciens virD2: tyrosine 29 is essential for endonuclease activity [8].
• Restriction endonuclease mapping of the octopine tumor-inducing plasmid pTiAch5 of Agrobacterium tumefaciens [9].

Biological context of virD2

• Comparative nucleotide sequence analyses of virD2 showed that the first 684 bp were 81% homologous to virD2 of an octopine Ti plasmid whereas the remaining 660 bp were only 44% homologous [1].
• However, a non-polar insertion immediately after bp 684 of the 1344 bp open reading frame of virD2 did not inhibit endonucleolytic cleavage but still caused a loss of virulence [1].
• Some insertional mutations in virD2 prevented T-DNA border endonucleolytic cleavage and produced an avirulent phenotype [1].
• To test this system, we introduced a wild-type virD2 gene into the A. tumefaciens chromosome at the pgl/picA locus [10].
• 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 [11].

Associations of virD2 with chemical compounds

• A T-DNA subfragment cloned in pBR322 is cleaved by a restriction endonuclease at a unique central site and target DNA (a kanamycin resistance marker) is ligated into this site [12].

Other interactions of virD2

• The regions within virD2 contributing to T-DNA processing and virulence were investigated [1].
• When extra copies of the virD1 and virD2 genes were present in an A. tumefaciens strain carrying a Ti plasmid, increased amounts of T-strand and nicked molecules could be detected at early stages of vir induction [13].
• The virD2 and ipt primer pairs did not interfere with each other when included in the same PCR amplification, and this permitted simultaneous detection of both genes in a single reaction [14].
• We propose that product(s) of this gene have recombinase or endonuclease activity which specifically recognizes the 25 bp terminal repeats of T-DNA [15].

Analytical, diagnostic and therapeutic context of virD2

• Analysis of deletion derivatives in Escherichia coli, immunoprecipitation, and a procedure combining immunoblot and nucleic acid hybridization data identified this protein as the gene product of virD2 [16].
• Restriction endonuclease mapping of a plasmid that confers oncogenicity upon Agrobacterium tumefaciens strain B6-806 [17].
• Transcription ternary complexes were subjected to electrophoresis on agarose gels, prior and/or subsequent to restriction endonuclease digestion of the DNA template, evidenced by autoradiography and located on the restriction maps of the two tumor-inducing plasmids [18].

References