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Gene Review

virA  -  two-component VirA-like sensor kinase

Agrobacterium tumefaciens

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Disease relevance of virA


High impact information on virA

  • Introduction of fragments of the C58 (nopaline-type) Ti plasmid into strains containing an octopine-type Ti plasmid showed that a fragment containing the nopaline-type virA locus was able to complement these normally non-agroinfectious strains to high levels of MSV DNA transfer [3].
  • Octopine-type virA mutant strains that express vir genes at high levels in the absence of the plant inducing compound acetosyringone also efficiently transferred MSV DNA [3].
  • These findings imply a functional difference between the virA gene products encoded by octopine- and nopaline-type Ti plasmids which has a profound effect on their ability to mediate DNA transfer to maize [3].
  • To investigate the signal pathway of the enhancement by the sugars, we first isolated a virA mutant of Agrobacterium with a base substitution mutation that caused a single amino acid change in the periplasmic domain [4].
  • 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 [5].

Chemical compound and disease context of virA


Biological context of virA

  • 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 [1].
  • The processes of transgene integration and transgene expression were suppressed when Agrobacteria contained mutated virA, virB or virG genes, suggesting that Agrobacterium transforms sea urchin cells by a mechanism similar to that which mediates T-DNA transfer to plants [7].
  • The Ti plasmid and virA source are shown to be important in determining the ability of a strain to infect maize, and the monosaccharide binding protein ChvE is absolutely required for maize agroinfection [8].

Associations of virA with chemical compounds

  • Since the trp promoter is not under virA-virG control, this result indicates that modification of VirG is necessary for its full activity [1].

Other interactions of virA

  • The analysis of the plasmid Ti encoded regions between the tmr and nos genes, and the virA and virB2 genes, allowed fingerprinting of Ti plasmids [9].
  • The vir region covering 30.2-kb has found to be composed of 21 genes resembling virH1, virA, virB1-11, virG, virC1-2, and virD1-5 [10].


  1. 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]
  2. 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]
  3. VirA, the plant-signal receptor, is responsible for the Ti plasmid-specific transfer of DNA to maize by Agrobacterium. Raineri, D.M., Boulton, M.I., Davies, J.W., Nester, E.W. Proc. Natl. Acad. Sci. U.S.A. (1993) [Pubmed]
  4. Genetic evidence for an interaction between the VirA sensor protein and the ChvE sugar-binding protein of Agrobacterium. Shimoda, N., Toyoda-Yamamoto, A., Aoki, S., Machida, Y. J. Biol. Chem. (1993) [Pubmed]
  5. 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]
  6. Characterization of the virA gene of the agropine-type plasmid pRiA4 of Agrobacterium rhizogenes. Endoh, H., Hirayama, T., Aoyama, T., Oka, A. FEBS Lett. (1990) [Pubmed]
  7. Agrobacterium-mediated transformation of sea urchin embryos. Bulgakov, V.P., Kiselev, K.V., Yakovlev, K.V., Zhuravlev, Y.N., Gontcharov, A.A., Odintsova, N.A. Biotechnology journal. (2006) [Pubmed]
  8. Discrete regions of the sensor protein virA determine the strain-specific ability of Agrobacterium to agroinfect maize. Heath, J.D., Boulton, M.I., Raineri, D.M., Doty, S.L., Mushegian, A.R., Charles, T.C., Davies, J.W., Nester, E.W. Mol. Plant Microbe Interact. (1997) [Pubmed]
  9. Identification of Agrobacterium strains by PCR-RFLP analysis of pTi and chromosomal regions. Ponsonnet, C., Nesme, X. Arch. Microbiol. (1994) [Pubmed]
  10. Genome structure of Ri plasmid (3). Sequencing analysis of the vir region of pRi1724 in Japanese Agrobacterium rhizogenes. Satuti, N., Moriguchi, K., Sato, M., Kataoka, M., Maeda, Y., Tanaka, N., Yoshida, K. Nucleic Acids Symp. Ser. (2000) [Pubmed]
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