scholarly journals PecS and PecT Coregulate the Synthesis of HrpN and Pectate Lyases, Two Virulence Determinants in Erwinia chrysanthemi 3937

2005 ◽  
Vol 18 (11) ◽  
pp. 1205-1214 ◽  
Author(s):  
William Nasser ◽  
Sylvie Reverchon ◽  
Regine Vedel ◽  
Martine Boccara
Keyword(s):  
Regulatory Region ◽  
Soft Rot ◽  
Erwinia Chrysanthemi ◽  
Virulence Determinants ◽  
Pectate Lyases ◽  
Heat Stable ◽  
Pectinolytic Enzymes ◽  
Transcript Elongation ◽  
Dna Protein Interaction

Erwinia chrysanthemi strain 3937 is a necrotrophic bacterial plant pathogen. Pectinolytic enzymes and, in particular, pectate lyases play a key role in soft rot symptoms; however, the efficient colonization of plants by E. chrysanthemi requires additional factors. These factors include HrpN (harpin), a heat-stable, glycine-rich hydrophilic protein, which is secreted by the type III secretion system. We investigated the expression of hrpN in E. chrysanthemi 3937 in various environmental conditions and different regulatory backgrounds. Using lacZ fusions, hrpN expression was markedly influenced by the carbon source, osmolarity, growth phase, and growth substrate. hrpN was repressed when pectinolysis started and negatively regulated by the repressors of ectate lyase synthesis, PecS and PecT. Primer extension data and in vitro DNA-protein interaction experiments support a model whereby PecS represses hrpN expression by binding to the hrpN regulatory region and inhibiting transcript elongation. The results suggest coordinated regulation of HrpN and pectate lyases by PecS and PecT. A putative model of the synthesis of these two virulence factors in E. chrysanthemi during pathogenesis is presented.

scholarly journals The Erwinia chrysanthemi 3937 PhoQ Sensor Kinase Regulates Several Virulence Determinants

2006 ◽  
Vol 188 (8) ◽  
pp. 3088-3098 ◽  
Author(s):  
Balakrishnan Venkatesh ◽  
Lavanya Babujee ◽  
Hui Liu ◽  
Pete Hedley ◽  
Takashi Fujikawa ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Regulatory System ◽  
Soft Rot ◽  
Erwinia Chrysanthemi ◽  
Pcr Analysis ◽  
Sensor Kinase ◽  
Virulence Determinants ◽  
Gene Encoding ◽  
Reverse Transcription Pcr ◽  
Two Component

ABSTRACT The PhoPQ two-component system regulates virulence factors in Erwinia chrysanthemi, a pectinolytic enterobacterium that causes soft rot in several plant species. We characterized the effect of a mutation in phoQ, the gene encoding the sensor kinase PhoQ of the PhoPQ two-component regulatory system, on the global transcriptional profile of E. chrysanthemi using cDNA microarrays and further confirmed our results by quantitative reverse transcription-PCR analysis. Our results indicate that a mutation in phoQ affects transcription of at least 40 genes, even in the absence of inducing conditions. Enhanced expression of several genes involved in iron metabolism was observed in the mutant, including that of the acs operon that is involved in achromobactin biosynthesis and transport. This siderophore is required for full virulence of E. chrysanthemi, and its expression is governed by the global repressor protein Fur. Changes in gene expression were also observed for membrane transporters, stress-related genes, toxins, and transcriptional regulators. Our results indicate that the PhoPQ system governs the expression of several additional virulence factors and may also be involved in interactions with other regulatory systems.

scholarly journals Relative Effects on Virulence of Mutations in the sap, pel, and hrp Loci of Erwinia chrysanthemi

2001 ◽  
Vol 14 (3) ◽  
pp. 386-393 ◽  
Author(s):  
Emilia López-Solanilla ◽  
Arancha Llama-Palacios ◽  
Alan Collmer ◽  
Francisco García-Olmedo ◽  
Pablo Rodríguez-Palenzuela
Keyword(s):  
Antimicrobial Peptides ◽  
Hypersensitive Response ◽  
Double Mutant ◽  
Erwinia Chrysanthemi ◽  
Potato Tubers ◽  
Pectate Lyases

We constructed strains of Erwinia chrysanthemi EC16 with multiple mutations involving three virulence systems in this bacterium, namely pel (coding for the major pectate lyases pelABCE), hrp (hypersensitive response and pathogenicity), and sap (sensitivity to antimicrobial peptides). The relative effects on virulence of those mutations have been analyzed on potato tubers and chicory leaves. In potato tubers, the sap mutation (BT105) had a greater effect in the reduction of the virulence than the pel (CUCPB5006) and hrp (CUCPB5039) mutations. This reduction was similar to that observed in the pel-hrp double mutant (CUCPB5037). The analysis of the strains affected in Pel-Sap (BT106), Hrp-Sap (BT107), and Pel-Hrp-Sap (BT108) suggested that the effects of these mutations are additive. In chicory leaves, the mutation in the sap locus appeared to have a greater effect than in potato tubers. The competitive indices of strains BT105, UM1005 (Pel¯), CUCPB5039, and CUCPB5037 have been estimated in vivo and in vitro. These results indicate that the mutation in the hrp locus can be complemented in vivo by coinfection, whereas the mutations in pel and sap cannot.

scholarly journals Coupling of Iron Assimilation and Pectinolysis in Erwinia chrysanthemi 3937

2002 ◽  
Vol 15 (11) ◽  
pp. 1181-1191 ◽  
Author(s):  
Thierry Franza ◽  
Isabelle Michaud-Soret ◽  
Pierrette Piquerel ◽  
Dominique Expert
Keyword(s):  
Iron Transport ◽  
Molecular Mechanisms ◽  
Constitutive Expression ◽  
Erwinia Chrysanthemi ◽  
Activation Mechanism ◽  
Receptor Protein ◽  
Virulence Determinants ◽  
Pectate Lyases ◽  
Iron Assimilation ◽  
Genes Encoding

Two major virulence determinants of the plant-pathogenic enterobacterium Erwinia chrysanthemi strain 3937 are the production of pectate lyase enzymes that degrade plant cell walls and expression of two high-affinity iron uptake systems mediated by two structurally unrelated siderophores, chrysobactin and achromobactin. Low iron availability is a signal that triggers transcription of the genes encoding pectate lyases PelD and PelE as well as that of genes involved in iron transport. This metalloregulation is mediated by the transcriptional repressor Fur. In this study, we analyzed the molecular mechanisms of this control. We purified the Erwinia chrysanthemi Fur protein. Band shift assays showed that Fur specifically binds in vitro to the regulatory regions of the genes encoding the ferrichrysobactin outer membrane receptor Fct and the pectate lyases PelD and PelE. We identified the Fur-binding sites of these promoter regions by performing DNase I footprinting experiments. From these data, we propose that Fur could inhibit the activation of the pelD and pelE genes by the cAMP receptor protein CRP according to an anti-activation mechanism. To identify other possible effectors involved in this control, we screened a bank of insertion mutants for an increase in transcriptional activity of pelD and fct genes in response to iron limitation. We isolated a mutant affected in the kdgK gene encoding the 2-keto-3-deoxygluconate (KDG) kinase, an enzyme involved in pectin catabolism. The growth of this mutant in the presence of pectic compounds led to a constitutive expression of iron transport genes as well as complete derepression of the pectinolysis genes. This effect was caused by intracellular accumulation of KDG. However, the derepression of iron transport genes by KDG does not involve the KdgR regulator of pectinolysis genes, which uses KDG as inducer. Thus, in Erwinia chrysanthemi, iron depletion or presence of KDG induces transcription of the genes involved in iron assimilation and pectinolysis. These important pathogenicity functions are coregulated by responding to common signals encountered in planta.

scholarly journals Re-evaluation of a Neonatal Mouse Model of Infection With Enterotoxigenic Escherichia coli

2021 ◽  
Vol 12 ◽  
Author(s):  
Carla J. Carroll ◽  
Dianna M. Hocking ◽  
Kristy I. Azzopardi ◽  
Judyta Praszkier ◽  
Vicki Bennett-Wood ◽  
...  
Keyword(s):  
Animal Studies ◽  
Premature Mortality ◽  
Bacterial Virulence ◽  
Enterotoxigenic Escherichia Coli ◽  
Virulence Determinants ◽  
Middle Income ◽  
Neonatal Mice ◽  
Targeted Gene Deletion ◽  
Heat Stable

Enterotoxigenic E. coli (ETEC) is a common cause of diarrhea in children in low- and middle-income countries, and in travelers to these countries. ETEC is also an important cause of morbidity and premature mortality in piglets, calves, goat kids and lambs. The major virulence determinants of ETEC are enterotoxins and colonization factors, which enable the pathogen to colonize the small intestine and deliver enterotoxins, such as the heat-stable enterotoxins, STp and STh, to epithelial cells. Because most ETEC strains are host-specific, there are few convenient animal models to investigate the pathogenesis of ETEC infections or to evaluate specific anti-ETEC interventions, such as drugs and vaccines. An exception is ETEC strains bearing F41 pili, which mediate intestinal colonization of various young animals, including neonatal mice, to cause disease and in some cases death. In this study, we used the archetypal F41-producing bovine ETEC strain, B41 (O101:NM; K99, F41, STp) to validate and further explore the contribution of F41 and STp to bacterial virulence. By using targeted gene deletion and trans-complementation studies, augmented by whole genome sequencing, and in vitro and animal studies of virulence, we established that F41 mediates colonization of the mouse intestine and is essential for bacterial virulence. In addition, we showed for the first time that STp is as important as F41 for virulence. Together, these findings validate the use of neonatal mice to study the pathogenesis of F41-bearing ETEC and to investigate possible specific anti-ETEC interventions including vaccines that target heat-stable enterotoxins.

scholarly journals Regulation of pelD and pelE, Encoding Major Alkaline Pectate Lyases in Erwinia chrysanthemi: Involvement of the Main Transcriptional Factors

1999 ◽  
Vol 181 (19) ◽  
pp. 5948-5957 ◽  
Author(s):  
Carine Rouanet ◽  
Kinya Nomura ◽  
Shinji Tsuyumu ◽  
William Nasser
Keyword(s):  
Cyclic Amp ◽  
Plant Cell Wall ◽  
Regulatory Region ◽  
Erwinia Chrysanthemi ◽  
Receptor Protein ◽  
Major Constituent ◽  
Promoter Regions ◽  
Transcriptional Initiation ◽  
Phytopathogenic Bacterium

ABSTRACT The main virulence factors of the phytopathogenic bacteriumErwinia chrysanthemi are pectinases which attack pectin, the major constituent of the plant cell wall. Of these enzymes, the alkaline isoenzyme named PelD in strain 3937 and PelE in strain EC16 has been described as being particularly important, based on virulence studies of plants. Expression of the pelD andpelE genes is tightly modulated by various regulators, including the KdgR repressor and the cyclic AMP-cyclic AMP receptor protein (CRP) activator complex. The use of a lacZ reporter gene allowed us to quantify the repression of E. chrysanthemi 3937 pelD expression exerted by PecS, another repressor of pectinase synthesis. In vitro DNA-protein interaction experiments, centered on the pelD andpelE wild-type or pelE mutated promoter regions, allowed us to define precisely the sequences involved in the binding of these three regulators and of RNA polymerase (RNAP). These studies revealed an unusual binding of the KdgR repressor and suggested the presence of a UP (upstream) element in the pelD andpelE genes. Investigation of the simultaneous binding of CRP, KdgR, PecS, and the RNAP to the regulatory region of thepelD and pelE genes showed that (i) CRP and RNAP bind cooperatively, (ii) PecS partially inhibits binding of the CRP activator and of the CRP-RNAP complex, and (iii) KdgR stabilizes the binding of PecS and prevents transcriptional initiation by RNAP. Taken together, our data suggest that PecS attenuates pelDand pelE expression rather than acting as a true repressor like KdgR. Overall, control of the pelD andpelE genes of E. chrysanthemi appears to be both complex and novel.

scholarly journals Erwinia chrysanthemi Burk., McFadden and Dimock: A bacterial whorl and stalk rot pathogen of sorghum [Sorghum bicolor (L.) Moench.]

1969 ◽  
Vol 71 (3) ◽  
pp. 265-275
Author(s):  
Paul R. Hepperly ◽  
Ezequiel Ramos-Dávila
Keyword(s):  
Solanum Tuberosum L ◽  
Soft Rot ◽  
Saccharum Officinarum ◽  
Erwinia Chrysanthemi ◽  
Ananas Comosus ◽  
Stalk Rot ◽  
Zones Of Inhibition ◽  
Phenotypic Tests ◽  
Sorghum Bicolor L

A foul smelting soft rot of the upper stalk and leaves of sorghum was observed in Isabela, Puerto Rico, during the summer of 1985. The bacterium from infected rotting sorghum whorls was isolated in pure culture and inoculated to sorghum, maize (Zea mays L.), and sugarcane (Saccharum officinarum L.) in the field and to potato (Solanum tuberosum L.) and pineapple [Ananas comosus (L.) Merr.] in vitro. Results of pathogenicity and 23 phenotypic tests suggested Erwinia chrysanthemi p.v. zeae Burk., McFadden & Dimock as the causal agent of the bacterial whorl blight and stalk rot of sorghum. Twenty-two antibiotics were tested for in vitro control of our strain of the whorl blight pathogen. Zones of inhibition around antibiotic impregnated discs on bacteria, seeded on Muller Hinton Agar, showed high pathogen sensitivity to senociclin, chloramphenicol, kanamycin, gentamicin, carbenicillin, cefotaximine, tetracycline, amikacin, and tobramycin. Members of the penicillin family appeared ineffective for controlling this bacterium. TAM 428 and SC 120, dwarf sorghums with moist sweet stems, were severely damaged when fungicide treated. Mean incidence of visible bacterial whorl blight reached 25%. Yield losses ranged from 34 to 56%. Dry stemmed sorghums, SC 307 and SC 212, showed less than 5% whorl blight and no yield loss.

scholarly journals PehN, a Polygalacturonase Homologue with a Low Hydrolase Activity, Is Coregulated with the Other Erwinia chrysanthemi Polygalacturonases

2002 ◽  
Vol 184 (10) ◽  
pp. 2664-2673 ◽  
Author(s):  
Nicole Hugouvieux-Cotte-Pattat ◽  
Vladimir E. Shevchik ◽  
William Nasser
Keyword(s):  
Rna Polymerase ◽  
Direct Interaction ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Hydrolase Activity ◽  
Erwinia Chrysanthemi ◽  
Receptor Protein ◽  
Glycosyl Hydrolases ◽  
Pectate Lyases ◽  
Almost All

ABSTRACT Erwinia chrysanthemi 3937 secretes an arsenal of pectinolytic enzymes, including at least eight endo-pectate lyases encoded by pel genes, which play a major role in the soft-rot disease caused by this bacterium on various plants. E. chrysanthemi also produces some hydrolases that cleave pectin. Three adjacent hydrolase genes, pehV, pehW, and pehX, encoding exo-poly-α-d-galacturonosidases, have been characterized. These enzymes liberate digalacturonides from the nonreducing end of pectin. We report the identification of a novel gene, named pehN, encoding a protein homologous to the glycosyl hydrolases of family 28, which includes mainly polygalacturonases. PehN has a low hydrolase activity on polygalacturonate and on various pectins. PehN action favors the activity of the secreted endo-pectate lyases, mainly PelB and PelC, and that of the periplasmic exo-pectate lyase PelX. However, removal of the pehN gene does not significantly alter the virulence of E. chrysanthemi. Regulation of pehN transcription was analyzed by using gene fusions. Like other pectinase genes, pehN transcription is dependent on several environmental conditions. It is induced by pectic catabolic products and is affected by growth phase, catabolite repression, osmolarity, anaerobiosis, nitrogen starvation, and the presence of calcium ions. The transcription of pehN is modulated by the repressor KdgR, which controls almost all the steps of pectin catabolism, and by cyclic AMP receptor protein (CRP), the global activator of sugar catabolism. The regulator PecS, which represses the transcription of the pel genes but activates that of pehV, pehW, and pehX, also activates transcription of pehN. The three regulators KdgR, PecS, and CRP act by direct interaction with the pehN promoter region. The sequences involved in the binding of these three regulators and of RNA polymerase have been precisely defined. Analysis of the simultaneous binding of these proteins indicates that CRP and RNA polymerase bind cooperatively and that the binding of KdgR could prevent pehN transcription. In contrast, the activator effect of PecS is not linked to competition with KdgR or to cooperation with CRP or RNA polymerase. This effect probably results from competition between PecS and an unidentified repressor involved in peh regulation.

scholarly journals An FNR-Type Regulator Controls the Anaerobic Expression of Hyn Hydrogenase in Thiocapsa roseopersicina

2005 ◽  
Vol 187 (8) ◽  
pp. 2618-2627 ◽  
Author(s):  
Ákos T. Kovács ◽  
Gábor Rákhely ◽  
Douglas F. Browning ◽  
András Fülöp ◽  
Gergely Maróti ◽  
...  
Keyword(s):  
Transcription Initiation ◽  
Regulatory Region ◽  
Photosynthetic Bacterium ◽  
Knockout Mutant ◽  
E Coli ◽  
Thiocapsa Roseopersicina ◽  
Heat Stable ◽  
Fnr Protein ◽  
Operon Expression

ABSTRACT The purple sulfur photosynthetic bacterium Thiocapsa roseopersicina BBS contains a heat-stable membrane-associated hydrogenase encoded by the hyn operon. Expression from the hyn operon regulatory region is up-regulated under anaerobic conditions. cis elements were mapped between positions −602 and −514 upstream from the hynS gene. Within this region two sequences that resemble DNA sites for FNR were recognized. The gene of an FNR homologue, FnrT, was identified in the genome of T. roseopersicina, and an fnrT knockout mutant was constructed. Anaerobic induction of hynS expression was abolished in the fnrT mutant, suggesting that FnrT is an activator of the hynS promoter. The T. roseopersicina hynS promoter could be activated in Escherichia coli, and this regulation was dependent on E. coli FNR. In vitro experiments with purified E. coli Ala154 FNR protein and purified E. coli RNA polymerase showed that FNR bound to two sites in the hyn regulatory region, that FNR could activate transcription initiation at the hynS promoter, and that FNR bound at the two target sites activated to different extents.

scholarly journals Characterization of the Exopolygalacturonate Lyase PelX of Erwinia chrysanthemi 3937

1999 ◽  
Vol 181 (5) ◽  
pp. 1652-1663 ◽  
Author(s):  
Vladimir E. Shevchik ◽  
Harry C. M. Kester ◽  
Jacques A. E. Benen ◽  
Jaap Visser ◽  
Janine Robert-Baudouy ◽  
...  
Keyword(s):  
Pectate Lyase ◽  
Erwinia Chrysanthemi ◽  
Receptor Protein ◽  
Polymeric Chain ◽  
Pectate Lyases ◽  
Pectinolytic Enzymes ◽  
Terminal Amino ◽  
Almost All ◽  
Binding Subsites

ABSTRACT Erwinia chrysanthemi 3937 secretes several pectinolytic enzymes, among which eight isoenzymes of pectate lyases with an endo-cleaving mode (PelA, PelB, PelC, PelD, PelE, PelI, PelL, and PelZ) have been identified. Two exo-cleaving enzymes, the exopolygalacturonate lyase, PelX, and an exo-poly-α-d-galacturonosidase, PehX, have been previously identified in other E. chrysanthemi strains. Using a genomic bank of a 3937 mutant with the major pelgenes deleted, we cloned a pectinase gene identified aspelX, encoding the exopolygalacturonate lyase. The deduced amino acid sequence of the 3937 PelX is very similar to the PelX of another E. chrysanthemi strain, EC16, except in the 43 C-terminal amino acids. PelX also has homology to the endo-pectate lyase PelL of E. chrysanthemi but has a N-terminal extension of 324 residues. The transcription of pelX, analyzed by gene fusions, is dependent on several environmental conditions. It is induced by pectic catabolic products and affected by growth phase, oxygen limitation, nitrogen starvation, and catabolite repression. Regulation of pelX expression is dependent on the KdgR repressor, which controls almost all the steps of pectin catabolism, and on the global activator of sugar catabolism, cyclic AMP receptor protein. In contrast, PecS and PecT, two repressors of the transcription of most pectate lyase genes, are not involved inpelX expression. The pelX mutant displayed reduced pathogenicity on chicory leaves, but its virulence on potato tubers or Saintpaulia ionantha plants did not appear to be affected. The purified PelX protein has no maceration activity on plant tissues. Tetragalacturonate is the best substrate of PelX, but PelX also has good activity on longer oligomers. Therefore, the estimated number of binding subsites for PelX is 4, extending from subsites −2 to +2. PelX and PehX were shown to be localized in the periplasm ofE. chrysanthemi 3937. PelX catalyzed the formation of unsaturated digalacturonates by attack from the reducing end of the substrate, while PehX released digalacturonates by attack from the nonreducing end of the substrate. Thus, the two types of exo-degrading enzymes appeared complementary in the degradation of pectic polymers, since they act on both extremities of the polymeric chain.

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