Disease relevance of chvB

• In contrast to wild-type Agrobacterium tumefaciens strains, beta-1,2-glucan-deficient chvB mutants were found to be unable to attach to pea root hair tips [1].
• Molecular cloning and characterization of cgs, the Brucella abortus cyclic beta(1-2) glucan synthetase gene: genetic complementation of Rhizobium meliloti ndvB and Agrobacterium tumefaciens chvB mutants [2].
• A DNA fragment from the chvB locus can hybridize to DNA from Azospirillum brasilense Sp7 [3].

High impact information on chvB

• Both attachment to root hairs and virulence of the chvB mutants could be restored by treatment of the plants with active rhicadhesin, whereas treatment of plants with beta-1,2-glucan had no effect on attachment or virulence [1].
• Moreover, nodulation ability of a chvB mutant carrying a Sym plasmid could be restored by pretreatment of the host plant with rhicadhesin [1].
• Apparently the attachment-minus and avirulence phenotype of chvB mutants is caused by lack of active rhicadhesin, rather than directly being caused by a deficiency in beta-1,2-glucan synthesis [1].
• Attachment, root colonization, and biofilm formation all were markedly reduced in celA and chvB mutants, deficient in production of cellulose and cyclic beta-(1,2)-D-glucans, respectively [4].
• Overproduction of cellulose by a nonattaching chvB mutant restored biofilm formation and bacterial attachment in microscopic and viable cell count assays and partially restored root colonization [4].

Chemical compound and disease context of chvB

• Agrobacterium tumefaciens chvB mutants are unable to produce beta-1,2 glucan [5].
• An octopine-type Ti plasmid, resident in different Agrobacterium tumefaciens chvB mutants, transferred at normal frequencies, demonstrating that this virulence locus affecting plant cell binding is not required for Ti plasmid conjugation [6].
• Studies performed with crude membrane preparations showed that cyclic 1,2-beta-glucan synthetase of BRUCELLA: spp. was not inhibited by 0.5 M KCl or potassium glutamate; concentrations that completely inhibit the osmosensitive enzymes of A. tumefaciens A348 or R. meliloti 102F34, respectively encoded by the chvB or ndvB genes [7].

Biological context of chvB

• The chvB operon of Agrobacterium tumefaciens is required for bacterial attachment to plant cells and for efficient crown gall tumor formation [8].
• A plasmid that contains only the phenotypically defined chvB operon also codes for a truncated protein [8].
• Expression of the Agrobacterium tumefaciens chvB virulence region in Azospirillum spp [9].
• Inner membranes of A. brasilense strains carrying a cosmid containing the chromosomal virulence genes chvA and chvB of Agrobacterium tumefaciens formed beta-(1-2) glucan in vitro and synthesized the 235-kilodalton intermediate protein [9].

Anatomical context of chvB

• Strains with mutations in the chvA or chvB gene do not accumulate beta-1,2-glucan in their periplasm and exhibit pleiotropic phenotypes, including inability to form crown gall tumors on plants [10].

Associations of chvB with chemical compounds

• Whereas chvB is required for beta-1,2-glucan synthesis, the role of chvA in glucan synthesis or export has not been clearly defined [11].
• Moreover, whereas chvB mutants grown in tryptone-yeast extract medium containing 7 mM CaCl2 do not produce active rhicadhesin, addition of 100 mM NaCl to this medium resulted in restoration of rhicadhesin activity [12].

References