Characterization of the virA locus of Agrobacterium tumefaciens: a transcriptional regulator and host range determinant.

Leroux, B.; Yanofsky, Martin F.; Winans, Stephen C.; Ward, J E; Ziegler, Steven F.; Nester, Eugene W.

doi:10.1002/j.1460-2075.1987.tb04830.x

Cited by 210 publications

(125 citation statements)

References 57 publications

Supporting

Mentioning

122

Contrasting

Unclassified

Order By: Relevance

“…Binding of 2-deoxy-D-glucose to GBP1 was slightly above background levels. L-Arabinose was not tested for binding to GBP1, but it induces the synthesis of GBP in E. coli, presumably by virtue of structural analogy to galactose (27) (24) and Trg (25). The positions of the homologous regions within each amino acid sequence and the site of the trg-8 mutation are indicated.…”

Section: Methodsmentioning

confidence: 99%

Sugars induce the Agrobacterium virulence genes through a periplasmic binding protein and a transmembrane signal protein.

Cangelosi

Ankenbauer

Nester

1990

Proc. Natl. Acad. Sci. U.S.A.

302

269

View full text Add to dashboard Cite

Phenolic plant metabolites such as acetosyringone induce transcription of the virulence (vir) genes of Agrobactrium tumefaciens through the transmembrane VirA protein. We report here that certain sugars induce the vir genes synergistically with phenolic inducers by way of a distinct regulatory pathway that includes VirA and a chromosomally encoded virulence protein, ChvE. Sequence comparison showed that ChvE is a periplasmic galactose-binding protein corresponding to the GBP1 protein isolated from Agrobacterium radiobacter. Like homologous sugar-binding proteins in Escherichia coli, ChvE was required for chemotaxis toward galactose and several other -sugars. These sugars strongly induced vir gene expression in wild-type cells when acetosyringone was absent or present in low concentrations. Mutations in chvE abolished vir gene induction by sugars and resulted in a limited host range for infection but did not affect vir gene induction by acetosyringone. A mutant lacking the periplasmic domain of VirA exhibited the same regulatory phenotype and limited host range as chvE mutants. These data show that the vir genes are regulated by two separate classes of plant-derived inducers by way of distinct regulatory pathways that can be separated by mutation. Induction by sugars is essential for infection of some but not all plant hosts.Ti plasmids in Agrobacterium tumefaciens strains carry >20 virulence (vir) genes that code for most of the proteins involved in crown gall infection of wound sites on dicotyledonous plants. The biology of crown gall tumorigenesis, which involves transfer and integration of a piece of bacterial DNA into the host plant genome, has been reviewed recently (1,2). The vir genes are induced by phenolic plant metabolites such as acetosyringone. Two Ti plasmid gene products, the

show abstract

Section: Methodsmentioning

confidence: 99%

Sugars induce the Agrobacterium virulence genes through a periplasmic binding protein and a transmembrane signal protein.

Cangelosi

Ankenbauer

Nester

1990

Proc. Natl. Acad. Sci. U.S.A.

302

269

View full text Add to dashboard Cite

show abstract

“…The radioactive material was prepared as above or preferably by iodinating in the final step. a-Bromoacetovanillone (AVBr) was prepared by the same procedure as ASBr (12) (17). This Kpn I fragment was replaced with a kanamycin-resistance (Kanr) cartridge obtained from plasmid pKISS (Pharmacia) to give pVRA6.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of activation of Agrobacterium virulence genes: identification of phenol-binding proteins.

Lee

Dudley

Hess

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Agrobacterium tumefaciens initiates the expression of pathogenic genes (vir genes) in response to hostderived phenolic signals through a two-component regulatory system consisting of VirA and VirG. a-Bromoacetosyringone (ASBr) was developed as an inhibitor of this induction process and found to be a specific and irreversible inhibitor of vir gene induction in this pathogen. Formal replacement of one of the methoxy groups of ASBr with Iodine gave an equally effective inhibitor that could carry an 'mI label. We report here that the resulting radiolabeled inhibitor does not react with the sensory component of this system, VirA, either in vivo or in vitro. Rather, two small proteins, p1O and p2l, bind labeled inhibitor in vivo in a time period that is consistent with the exposure time required for the inhibition of vir gene expression. Labeling to these proteins was protected by preexposure to ASBr but not by a-bromo-3,5-dlmethoxyacetophenone, a compound of comparable chemical reactivity but previously shown not to inhibit vir gene expression. Our findings suggest that proteins that are not tumor-inducing plasmid-encoded mediate vir gene activation in a step prior to the VirA/VirG two-component regulatory system. Agrobacterium tumefaciens is the causative agent of crown gall tumors, a neoplastic disease of many dicotyledonous plants (1,2). A small oncogenic segment [transferred DNA (T-DNA)] of the tumor-inducing (Ti) plasmid harbored by these bacteria is transferred to the host cell, inducing the disease state. Many ofthe genes of the virulence regulon (vir) of the Ti plasmid required for this transfer are only expressed in the presence of host-derived phenolic compounds (3), one of which has been implicated in the control of division in the host cell (4-6).Sequence homology of two constitutively expressed genes of the vir regulon, virA and virG, with what now appears to be a large family of procaryotic two-component regulatory proteins (7) led to the proposal that these proteins served as the sensor/response elements controlling vir expression (8).This model predicts that VirA would interact with the phenolic inducer as the initiation step. Autophosphorylation in the C-terminal cytoplasmic domain of VirA (9, 10) and subsequent phosphate transfer to the transcriptional regulator, VirG (11), have been demonstrated in vitro and together constitute a phenol-activated signaling pathway. At least two other environmental stimuli, acidic pH and monosaccharides, act synergistically with the phenolic signals to activate vir gene expression (2).The dissection of the structures of these phenolic inducers has provided sufficient insight for the development of specific, irreversible inhibitors of vir gene expression (12). We now provide evidence that these inhibitors do not interact directly with VirA but rather with two other proteins, p10 and p21. We propose that these chromosomally encoded proteins modulate the signal transduction pathway prior to the autophosphorylation of VirA. MATERIALS AND METHODS Syntheses. a-Bro...

show abstract

“…The total membrane pellet was suspended in 1 ml of ice-cold P04 buffer by sonication for three 20-s intervals with an extrafine microtip probe at a power setting of 4 (Heat Systems-Ultrasonics, Inc., Farmingdale, N.Y.). The volume was brought up to 5.5 ml with P04 buffer, and the membranes were repelleted at 150,000 x g for 1 h. Membranes were suspended in 1 ml of 20% sucrose (wt/vol)-3 mM EDTA-0.2 mM dithiothreitol by sonication, and inner and outer membranes were separated by isopycnic sucrose gradient centrifugation (17). Methods for isolation of the periplasmic protein fraction were as described previously (7).…”

mentioning

confidence: 99%

Identification of a virB10 protein aggregate in the inner membrane of Agrobacterium tumefaciens

et al. 1990

View full text Add to dashboard Cite

Characterization of the virA locus of Agrobacterium tumefaciens: a transcriptional regulator and host range determinant.

Cited by 210 publications

References 57 publications

Sugars induce the Agrobacterium virulence genes through a periplasmic binding protein and a transmembrane signal protein.

Sugars induce the Agrobacterium virulence genes through a periplasmic binding protein and a transmembrane signal protein.

Mechanism of activation of Agrobacterium virulence genes: identification of phenol-binding proteins.

Identification of a virB10 protein aggregate in the inner membrane of Agrobacterium tumefaciens

Contact Info

Product

Resources

About