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Gene Review:

virA - two-component VirA-like sensor kinase

Agrobacterium fabrum str. C58

Lohrke, S.M. et al., Pazour, G.J. et al., Bélanger, C. et al., Krishnamohan, A. et al., Hubber, A.M. et al., et al.

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Disease relevance of virA

Efficient vir gene induction in Agrobacterium tumefaciens requires virA, virG, and vir box from the same Ti plasmid [1].
However, virA and virG are insufficient to activate transcription from virulence gene promoters within Escherichia coli cells, indicating a requirement for additional A. tumefaciens genes [2].

High impact information on virA

When a deletion was introduced into the virA gene in the region encoding the periplasmic portion of the VirA protein, enhancement by glucose disappeared, but vir expression was induced by acetosyringone in this mutant [3].
This activation was dependent on a nod box present 851 bp upstream of virA, and a mutant with the nod box deleted formed effective nodules on Leucaena leucocephala, the same symbiotic phenotype as other M. loti vir mutants [4].
Following conjugative transfer of certain Ti plasmids to a new agrobacterial host, evolution of the newly introduced virA, or coevolution of chvE and virA, may lead to optimization of ChvE-VirA interaction and vir gene induction levels [5].
Element IS426 was no longer found in the arginine and nopaline catabolism region of the Ti plasmids from the virA and virG mutants, but it resided in the particular KpnI fragment containing the modified vir locus [6].
Since the trp promoter is not under virA-virG control, this result indicates that modification of VirG is necessary for its full activity [7].

Chemical compound and disease context of virA

Agrobacterium cells containing this gene fusion showed a large increase in virG activity in the presence of virA and acetosyringone [7].

Biological context of virA

Efficient vir gene induction in octopine and nopaline strains requires virA, virG, and vir boxes from the respective Ti plasmids [1].
It was found to be a DNA-binding protein that preferentially bound DNA fragments containing the 5' nontranscribed regions of the virA, -B, -C, -D, and -G operons [7].

Other interactions of virA

To verify this hypothesis, D10B/87 and C58 virA were compared, and conclusions from this first set of analyses were then corroborated by comparing D10B/87 and C58 chvE [5].

References

Efficient vir gene induction in Agrobacterium tumefaciens requires virA, virG, and vir box from the same Ti plasmid. Krishnamohan, A., Balaji, V., Veluthambi, K. J. Bacteriol. (2001) [Pubmed]
Transcriptional activation of Agrobacterium tumefaciens virulence gene promoters in Escherichia coli requires the A. tumefaciens RpoA gene, encoding the alpha subunit of RNA polymerase. Lohrke, S.M., Nechaev, S., Yang, H., Severinov, K., Jin, S.J. J. Bacteriol. (1999) [Pubmed]
Control of expression of Agrobacterium vir genes by synergistic actions of phenolic signal molecules and monosaccharides. Shimoda, N., Toyoda-Yamamoto, A., Nagamine, J., Usami, S., Katayama, M., Sakagami, Y., Machida, Y. Proc. Natl. Acad. Sci. U.S.A. (1990) [Pubmed]
Symbiosis-induced cascade regulation of the Mesorhizobium loti R7A VirB/D4 type IV secretion system. Hubber, A.M., Sullivan, J.T., Ronson, C.W. Mol. Plant Microbe Interact. (2007) [Pubmed]
Variable efficiency of a Ti plasmid-encoded VirA protein in different agrobacterial hosts. Bélanger, C., Loubens, I., Nester, E.W., Dion, P. J. Bacteriol. (1997) [Pubmed]
Dynamic structure of Agrobacterium tumefaciens Ti plasmids. Fortin, C., Marquis, C., Nester, E.W., Dion, P. J. Bacteriol. (1993) [Pubmed]
virG, an Agrobacterium tumefaciens transcriptional activator, initiates translation at a UUG codon and is a sequence-specific DNA-binding protein. Pazour, G.J., Das, A. J. Bacteriol. (1990) [Pubmed]

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