Disease relevance of virG

• Nucleotide sequence of the virG locus of the Agrobacterium tumefaciens plasmid pTiC58 [1].
• To study the role of the VirG protein in the activation process, we overproduced the native-sized VirG protein in Escherichia coli by fusing the lacZ' start codon ATG with the second virG codon AAA using site-directed mutagenesis [2].

High impact information on virG

• We also tested whether supplying Agrobacterium with a similar plasmid containing wild-type virG affects the efficiency of T-DNA transfer [3].
• Using a beta-glucuronidase (GUS) reporter gene to assess transient expression of T-DNA after transfer to tobacco and maize tissues, we observed a higher frequency of GUS-expressing foci after inoculation with Agrobacterium strains carrying virGN54D than with Agrobacterium carrying the wild-type virG [3].
• Agrobacterium A136 harboring plasmid pGP159, which contains virA, virG, and a reporter virB:lacZ gene fusion, was mutagenized with UV light or nitrosoguanidine [4].
• The nucleic acid sequence of a 1.25-kilobase clone encompassing virG contains one open reading frame capable of coding for a protein of about 30,000 daltons [5].
• The amino acid sequence of the predicted virG product is homologous to that of eight bacterial proteins, including that of the ompR gene of Escherichia coli [5].

Chemical compound and disease context of virG

• The nucleotide sequence of the virG locus of the nopaline type plasmid pTiC58 of Agrobacterium tumefaciens has been determined [1].
• Virulence genes of Agrobacterium tumefaciens are induced in parallel in the presence of plant phenolic compounds such as acetosyringone and the two regulatory vir genes virA and virG [2].
• The entire nucleotide sequence of the virG locus, from the octopine Ti plasmid of Agrobacterium tumefaciens strain 15955, has been determined [6].

Biological context of virG

• It contains an open reading frame (ORF) of 759 nucleotides and has 77% homology to the virG sequences of octopine type plasmids [1].
• The amino acid sequences inferred from the two virG genes show 80% homology to each other and each shows the same moderate homologies to amino acid sequences derived from genes in a family of two-component regulatory systems [1].
• Differences between the sequences of the two types of Ti plasmids in the region of virG are located predominantly outside the ORF [1].
• This fragment contains the virG locus, as well as the 3' end of the virB operon [7].
• Agrobacterium cells containing this gene fusion showed a large increase in virG activity in the presence of virA and acetosyringone [8].

Anatomical context of virG

• The virG gene is involved in the transcriptional activation of the Ti plasmid vir-loci, which occurs after induction by specific compounds present in plant exudate [6].
• Several vir genes contain two common hexanucleotide sequences, 5'CGAGTA3' and 5'GCAATT3'. Translation initiation codons for all vir genes, except virG, are preceded by sequences homologous to the ribosome binding site sequences found in E. coli [9].

Associations of virG with chemical compounds

• This attracts Ti-plasmid harbouring A. tumefaciens to wound sites, where the higher acetosyringone concentrations lead to virA and virG-mediated induction of the vir-genes [10].
• Multiple copies of virG genes contained in A. tumefaciens strains harboring a nopaline-type Ti-plasmid had a smaller enhancing effect upon the transformation of celery tissues, and no enhancing effect upon the transformation of rice [11].
• Additional copies of octopine- and agropine-type virG genes in A. tumefaciens strains containing an agropine-type Ti-plasmid enhanced the frequency of transient transformation of celery and rice [11].
• Since the trp promoter is not under virA-virG control, this result indicates that modification of VirG is necessary for its full activity [8].

Other interactions of virG

• Generally, the mutants of the apple isolate D10B/87 were altered in the tumor-inducing plasmid, harboring either deletions in this plasmid or point mutations in the regulatory virulence gene virG [12].

References