Disease relevance of virG

• virA and virG are the Ti-plasmid functions required for chemotaxis of Agrobacterium tumefaciens towards acetosyringone [1].
• Controlled expression of the transcriptional activator gene virG in Agrobacterium tumefaciens by using the Escherichia coli lac promoter [2].

High impact information on virG

• However, Ti-plasmids with mutations in virA or virG were unable to confer the responsive phenotype [1].
• Of the cosmid clones pVK219 (virAB) pVK221 (virBGC) pVK225 (virGCDE) and pVK257 (virABGC) mobilized to cured A. tumefaciens C58C1, only pVK257 bestowed acetosyringone chemotaxis. virA and virG are thus required for chemotaxis of A. tumefaciens towards acetosyringone [1].
• Efficient vir gene induction in Agrobacterium tumefaciens requires virA, virG, and vir box from the same Ti plasmid [3].
• The ability of Bo542 virG to bring about supervirulence in tobacco is observed for an octopine vir helper (LBA4404) but not for a nopaline vir helper (PMP90) [3].
• Resection and mutagenesis of the acid pH-inducible P2 promoter of the Agrobacterium tumefaciens virG gene [4].

Biological context of virG

• Random chemical mutagenesis of single-stranded DNA containing the Agrobacterium tumefaciens virG gene led with high frequency to the inactivation of the gene [5].
• This pH control of vir gene expression was shown to act at the level of expression of virG, which was the limiting factor [6].
• Sequence analysis showed that 29% of the mutants contained a virG gene with one single-base-pair substitution somewhere in the open reading frame [5].
• Furthermore, two virG mutants, with amino acid substitutions of G56V/V7I/I106N and G56V/I77V, respectively, are capable of activating vir genes in E. coli in response to inducer acetosyringone in a virA-dependent manner, demonstrating that the interaction site between VirG and RpoA is separable from that of VirG and VirA [7].
• We identified complete nucleotide sequence of virG of pTiKU12, an octopine Ti plasmid of this strain [8].

Associations of virG with chemical compounds

• Efficient vir gene induction in octopine and nopaline strains requires virA, virG, and vir boxes from the respective Ti plasmids [3].
• We also fused the lac promoter to a virG::lacZ translational fusion and found that IPTG elevated expression of this translational fusion to moderate levels, though not to levels as high as from the stronger of the two native virG promoters [2].
• Since the trp promoter is not under virA-virG control, this result indicates that modification of VirG is necessary for its full activity [9].

Other interactions of virG

• The virA and virG gene products are required for the regulation of the vir regulon on the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens [10].
• Altered-function mutations of the transcriptional regulatory gene virG of Agrobacterium tumefaciens [11].
• Molecular characterization of the virulence gene virG of pTiKU 12 [8].

References