Disease relevance of virA

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

• 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

• Characterization of the virA gene of the agropine-type plasmid pRiA4 of Agrobacterium rhizogenes [6].

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].

References