Identification of a locus that regulates multiple functions in Pseudomonas solanacearum

Huang, Yong

doi:10.1128/jb.172.8.4728-4731.1990

Cited by 20 publications

(11 citation statements)

References 15 publications

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“…The sequence of the ops gene has not been reported, but ops mutants differ from our exoR mutants in that they only overproduce exopolysaccharide in minimal media (42), whereas exoR mutants are distinguished by their apparent uncoupling of control of exopolysaccharide production from medium composition (12). The epsR locus of Pseudomonas solanacearum also acts negatively (19), but its deduced amino acid sequence does not appear to be related to that of ExoR (22 . .…”

Section: Resultsmentioning

confidence: 83%

The exoR gene of Rhizobium meliloti affects RNA levels of other exo genes but lacks homology to known transcriptional regulators

1991

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Rhizobium melioti strains mutant in the exoR gene overproduce an exopolysaccharide called succinoglycan or EPS I. Protein fusions to several different exo genes required for EPS I biosynthesis are expressed at a higher level in an exoR strain than in a wild-type strain, showing that the overproduction of EPS I in exoR strains results at least in part from increased gene expression. This regulation is important to nodulation, since exoR mutants fail to invade alfalfa nodules unless secondary suppressor mutations that cause a decrease in EPS I production occur. Here, we show that an exoR strain contains higher levels of mRNA for other exo genes than does the wild-type parental strain. ExoR therefore most probably exerts its regulatory effect at the level of transcription. In addition, we have localized, subcloned, and sequenced the exoR gene. A newly constructed insertion allele of exoR has the same phenotype as the original mutant. The deduced sequence of ExoR is 268 amino acids long but does not show homology to other sequenced genes.

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Section: Resultsmentioning

confidence: 83%

The exoR gene of Rhizobium meliloti affects RNA levels of other exo genes but lacks homology to known transcriptional regulators

1991

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“…syringae, with Tn3::HoHo1 in its 3Ј end is functional (22). Similar loci which control the expression of multiple traits linked to the phenotypic variation have also been cloned from other plantpathogenic bacteria, including phcA and epsR in Pseudomonas solanacearum (8,24) and rpfC in X. campestris (52).…”

Section: Discussionmentioning

confidence: 99%

Identification and characterization of a locus which regulates multiple functions in Pseudomonas tolaasii, the cause of brown blotch disease of Agaricus bisporus

1995

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Pseudomonas tolaasii, the causal agent of brown blotch disease of Agaricus bisporus, spontaneously gives rise to morphologically distinct stable sectors, referred to as the phenotypic variant form, at the margins of the wild-type colonies. The phenotypic variant form is nonpathogenic and differs from the wild type in a range of biochemical and physiological characteristics. A genomic cosmid clone (pSISG29) from a wild-type P. tolaasii library was shown to be capable of restoring a range of characteristics of the phenotypic variant to those of the wild-type form, when present in trans. Subcloning and saturation mutagenesis analysis with Tn5lacZ localized a 3.0-kb region from pSISG29, designated the pheN locus, required for complementation of the phenotypic variant to the wild-type form. Pseudomonas tolaasii causes the economically important brown blotch disease of the mushroom Agaricus bisporus (Lange) Imbach (53). Synthesis of the low-molecular-weight (M r , 1,985) lipodepsipeptide extracellular toxin tolaasin by P. tolaasii is primarily responsible for eliciting disease symptoms (6,38,39). Tolaasin causes disruption of cell membranes from a range of cell types and has both ion channel-forming and biosurfactant properties (6,26,38). The ability of P. tolaasii to show a positive chemotactic response to A. bisporus exudates (20) and its ability to attach to mycelial surfaces (9, 35, 37) may also be important as steps in the early stages of development of brown blotch disease.P. tolaasii undergoes phenotypic variation, a strategy frequently used by bacteria to survive disparate environmental conditions. Old colonies of P. tolaasii frequently produce sectors which, when subcultured onto fresh medium, show different phenotypically distinct colonial forms (10, 29, 36). The wild-type strain is opaque, mucoid, pathogenic, and nonfluorescent, whereas the sectors are translucent, nonmucoid, nonpathogenic, and fluorescent (10, 57). In addition to alteration in virulence, qualitative analysis has revealed that a number of biochemical properties are also changed in the transition from the wild type to a phenotypic variant. These include the loss of the ability to produce tolaasin, hydrolyze casein, and grow normally on medium containing cetrimide (10). Finally, the variant form swims faster and shows a more rapid chemotactic response than the wild type (20). Phase change from the pathogenic to the nonpathogenic form in P. tolaasii has been referred to as a smooth-to-rough transition (10). This description generally designates a difference in the lipopolysaccharide (LPS) content of the two forms (16,29). Recent studies by Hutchison (25) have demonstrated that there is no difference in the LPS profiles of the smooth and rough forms of P. tolaasii. Therefore, the terms ''wild type'' and ''phenotypic variant'' are used here instead of ''smooth'' and ''rough,'' respectively.The aim of this study was to identify the molecular switch controlling the transition from the wild type to the phenotypic variant in P. tolaasii. First, we ...

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“…epsR encodes a putative DNA-binding protein that inhibits EPS production by R. solanacearum strain K60, but only when plasmid borne (18,25,30). Moreover, the two reported phenotypes of epsR mutants of strain K60 are contradictory (3,25).…”

Section: Vol 182 2000mentioning

confidence: 99%

“…Nonetheless, analogy to other two-component systems (17) implies that, in response to some unknown signal, VsrB phosphorylates VsrC, thereby stimulating it to turn on transcription, possibly via direct binding to P eps . EpsR, a putative DNA-binding protein, is another potential regulator of P eps , since its overproduction strongly represses EPS I synthesis by R. solanacearum strain K60 (18,25).…”

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confidence: 99%

Multicomponent Transcriptional Regulation at the Complex Promoter of the Exopolysaccharide I Biosynthetic Operon of Ralstonia solanacearum

Garg¹,

Huang²,

Yindeeyoungyeon³

et al. 2000

J Bacteriol

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High-level transcription of eps, an operon encoding biosynthesis of an exopolysaccharide virulence factor of the phytopathogen Ralstonia (Pseudomonas) solanacearum, requires the products of at least seven regulatory genes (phcA, phcB, xpsR, vsrA-vsrD, and vsrB-vsrC), which are organized in three converging signal transduction cascades. Because xpsR and the vsrB-vsrC two-component system are the most downstream cascade components required for activation of eps, we explored how these components control transcription from the eps promoter (P eps ). Deletion and PCR mutagenesis identified an upstream region of P eps (nucleotides ؊82 to ؊62) that is critical for transcription activation by VsrB-VsrC and XpsR and also is required for negative control of P eps by the putative eps regulator EpsR. Using PCR mutagenesis we generated the vsrC1 allele that encodes a response regulator that constitutively activates P eps in the absence of its cognate sensor, VsrB. However, activation of P eps by vsrC1 still required xpsR. Unexpectedly, the amino acid substitution conferring the constitutive phenotype on VsrC1 is 12 residues from its C terminus, outside the known functional domains of response regulators. Finally, a modified DNase I footprinting method was used to demonstrate specific binding of both VsrC1 and VsrC to the ؊72 to ؊62 upstream region of P eps .Ralstonia (Pseudomonas) solanacearum, which causes a lethal wilting disease of solanaceous and many other types of other plants (15, 16), enters hosts via natural openings or wounds in roots and then proceeds to extensively colonize xylem vessels of the vascular system (37, 44). Although secreted plant cell wall-degrading exoenzymes enhance virulence (possibly by facilitating invasion and vascular colonization [23,24,37]), it is exopolysaccharide I (EPS I), a large, nitrogenrich, acidic exopolysaccharide (34), that is the primary virulence factor of R. solanacearum. EPS I is produced in copious amounts and is required for wilting and killing of hosts (8,29). EPS I apparently causes wilting by restricting water flow through xylem vessels (6). It also markedly enhances the speed and extent of stem colonization (37).In R. solanacearum, production of EPS I (as well as some exoenzymes) is stringently controlled by a cascading network of more than 10 regulatory genes (5,11,20,41). Inactivation of any of seven genes in this network causes a Ͼ85% reduction in transcription from the eps promoter (P eps ), leading to loss of EPS I production and the ability to wilt and kill. However, inactivation of all but two of these genes (vsrB and vsrC) can be suppressed by constitutive expression of xpsR from a vector promoter (20). These and other data showed that VsrB, VsrC, and XpsR are the most downstream components in the eps regulatory cascade and suggested that they may directly affect interaction of RNA polymerase with P eps .The predicted amino acid sequences of VsrB and VsrC imply that they comprise a two-component system in which VsrB is a sensor kinase and VsrC is its cognate resp...

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Identification of a locus that regulates multiple functions in Pseudomonas solanacearum

Cited by 20 publications

References 15 publications

The exoR gene of Rhizobium meliloti affects RNA levels of other exo genes but lacks homology to known transcriptional regulators

The exoR gene of Rhizobium meliloti affects RNA levels of other exo genes but lacks homology to known transcriptional regulators

Identification and characterization of a locus which regulates multiple functions in Pseudomonas tolaasii, the cause of brown blotch disease of Agaricus bisporus

Multicomponent Transcriptional Regulation at the Complex Promoter of the Exopolysaccharide I Biosynthetic Operon of Ralstonia solanacearum

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