Faculty Opinions recommendation of Identification of the central quorum sensing regulator of virulence in the enteric phytopathogen, Erwinia carotovora: the VirR repressor.

Bacterial pheromones, mainly different homoserine lactones, are central to a number of bacterial signaling processes, including those involved in plant pathogenicity. We previously demonstrated that N-oxoacyl-homoserine lactone (OHL) is essential for quorum sensing in the soft-rot phytopathogen Erwinia carotovora. In this pathogen, OHL controls the coordinate activation of genes encoding the main virulence determinants, extracellular plant cell wall degrading enzymes (PCWDEs), in a cell density-dependent manner. We suggest that E. carotovora employ quorum sensing to avoid the premature production of PCWDEs and subsequent activation of plant defense responses. To test whether modulating this sensory system would affect the outcome of a plant-pathogen interaction, we generated transgenic tobacco, producing OHL. This was accomplished by ectopic expression in tobacco of the E. carotovora gene expI, which is responsible for OHL biosynthesis. We show that expI-positive transgenic tobacco lines produced the active pheromone and partially complemented the avirulent phenotype of expI mutants. The OHL-producing tobacco lines exhibited enhanced resistance to infection by wild-type E. carotovora. The results were confirmed by exogenous addition of OHL to wild-type plants, which also resulted in increased resistance to E. carotovora.

Download Full-text

Regulation of Motility in Erwinia carotovora subsp. carotovora: Quorum-Sensing Signal Controls FlhDC, the Global Regulator of Flagellar and Exoprotein Genes, by Modulating the Production of RsmA, an RNA-Binding Protein

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-01-10-0017 ◽

2010 ◽

Vol 23 (10) ◽

pp. 1316-1323 ◽

Cited By ~ 21

Author(s):

Asita Chatterjee ◽

Yaya Cui ◽

Pranjib Chakrabarty ◽

Arun K. Chatterjee

Keyword(s):

Quorum Sensing ◽

Rna Binding ◽

Binding Protein ◽

Rna Binding Protein ◽

Erwinia Carotovora ◽

Translational Repression ◽

Global Regulator ◽

Acylhomoserine Lactone ◽

Σ Factor ◽

Regulatory Effects

Erwinia carotovora subsp. carotovora causes soft-rotting (tissue-macerating) disease in many plants and plant organs. Although pectinases are the primary determinants of virulence, several ancillary factors that augment bacterial virulence have also been identified. One such factor is bacterial motility. Flagellum formation and bacterial movement are regulated in many enterobacteria, including E. carotovora subsp. carotovora, by FlhDC, the master regulator of flagellar genes and FliA, a flagellum-specific σ factor. We document here that motility of E. carotovora subsp. carotovora is positively regulated by the quorum-sensing signal, N-acylhomoserine lactone (AHL), and negatively regulated by RsmA, a post-transcriptional regulator. RsmA, an RNA-binding protein, causes translational repression and promotes RNA decay. Our data show that RsmA negatively regulates flhDC and fliA expression. Moreover, the chemical stabilities of transcripts of these genes are greater in an RsmA– mutant than in RsmA+ bacteria. These observations contrast with positive regulation of flhDC and motility by CsrA (= RsmA) in Escherichia coli. In the absence of AHL, the AHL receptors ExpR1/ExpR2 (= AhlR) in Erwinia carotovora subsp. carotovora negatively regulate motility and expression of flhDC and fliA by activating RsmA production. In the presence of AHL, regulatory effects of ExpR1/ExpR2 are neutralized, resulting in reduced levels of rsmA expression and enhanced motility.

Download Full-text

Elevated Temperature Enhances Virulence of Erwinia carotovora subsp. carotovora Strain EC153 to Plants and Stimulates Production of the Quorum Sensing Signal, N-Acyl Homoserine Lactone, and Extracellular Proteins

Applied and Environmental Microbiology ◽

10.1128/aem.71.8.4655-4663.2005 ◽

2005 ◽

Vol 71 (8) ◽

pp. 4655-4663 ◽

Cited By ~ 31

Author(s):

H. Hasegawa ◽

A. Chatterjee ◽

Y. Cui ◽

A. K. Chatterjee

Keyword(s):

Quorum Sensing ◽

Extracellular Enzymes ◽

Rna Binding ◽

Elevated Temperatures ◽

Pectate Lyase ◽

Erwinia Carotovora ◽

Homoserine Lactone ◽

Extracellular Proteins ◽

Acyl Homoserine Lactone ◽

Tissue Maceration

ABSTRACT Erwinia carotovora subsp. atroseptica, E. carotovora subsp. betavasculorum, and E. carotovora subsp. carotovora produce high levels of extracellular enzymes, such as pectate lyase (Pel), polygalacturonase (Peh), cellulase (Cel), and protease (Prt), and the quorum-sensing signal N-acyl-homoserine lactone (AHL) at 28°C. However, the production of these enzymes and AHL by these bacteria is severely inhibited during growth at elevated temperatures (31.2°C for E. carotovora subsp. atroseptica and 34.5°C for E. carotovora subsp. betavasculorum and most E. carotovora subsp. carotovora strains). At elevated temperatures these bacteria produce high levels of RsmA, an RNA binding protein that promotes RNA decay. E. carotovora subsp. carotovora strain EC153 is an exception in that it produces higher levels of Pel, Peh, Cel, and Prt at 34.5°C than at 28°C. EC153 also causes extensive maceration of celery petioles and Chinese cabbage leaves at 34.5°C, which correlates with a higher growth rate and higher levels of rRNA and AHL. The lack of pectinase production by E. carotovora subsp. carotovora strain Ecc71 at 34.5°C limits the growth of this organism in plant tissues and consequently impairs its ability to cause tissue maceration. Comparative studies with ahlI (the gene encoding a putative AHL synthase), pel-1, and peh-1 transcripts documented that at 34.5°C the RNAs are more stable in EC153 than in Ecc71. Our data reveal that overall metabolic activity, AHL levels, and mRNA stability are responsible for the higher levels of extracellular protein production and the enhanced virulence of EC153 at 34.5°C compared to 28°C.

Download Full-text

Mutations in rpsL that confer streptomycin resistance show pleiotropic effects on virulence and the production of a carbapenem antibiotic in Erwinia carotovora

Microbiology ◽

10.1099/mic.0.034595-0 ◽

2010 ◽

Vol 156 (4) ◽

pp. 1030-1039 ◽

Cited By ~ 18

Author(s):

Anne M. L. Barnard ◽

Natalie J. L. Simpson ◽

Kathryn S. Lilley ◽

George P. C. Salmond

Keyword(s):

Quorum Sensing ◽

Erwinia Carotovora ◽

Homoserine Lactone ◽

Base Change ◽

Signalling Molecule ◽

Intracellular Proteins ◽

Single Base Change ◽

Ribosomal Protein S12 ◽

Derivatives Of ◽

Carbapenem Antibiotic

Spontaneous streptomycin-resistant derivatives of Erwinia carotovora subsp. carotovora strain ATTn10 were isolated. Sequencing of the rpsL locus (encoding the ribosomal protein S12) showed that each mutant was missense, with a single base change, resulting in the substitution of the wild-type lysine by arginine, threonine or asparagine at codon 43. Phenotypic analyses showed that the rpsL mutants could be segregated into two groups: K43R mutants showed reduced production of the β-lactam secondary metabolite 1-carbapen-2-em-3 carboxylic acid (Car), but little effect on exoenzyme production or virulence in potato tuber tests. By contrast, the K43N and K43T mutations were pleiotropic, resulting in reduced exoenzyme production and virulence, as well as diminished Car production. The effect on Car production was due to reduced transcription of the quorum-sensing-dependent car biosynthetic genes. The effects of K43N and K43T mutations on Car production were partially alleviated by provision of an excess of the quorum-sensing signalling molecule N-(3-oxohexanoyl)-l-homoserine lactone. Finally, a proteomic analysis of the K43T mutant indicated that the abundance of a subset of intracellular proteins was affected by this rpsL mutation.

Download Full-text

Quorum-sensing inhibition by hexanal in biofilms formed by Erwinia carotovora and Pseudomonas fluorescens

LWT ◽

10.1016/j.lwt.2019.04.023 ◽

2019 ◽

Vol 109 ◽

pp. 145-152 ◽

Cited By ~ 2

Author(s):

Ying Zhang ◽

Jie Kong ◽

Yunfei Xie ◽

Yahui Guo ◽

Hang Yu ◽

...

Keyword(s):

Quorum Sensing ◽

Pseudomonas Fluorescens ◽

Erwinia Carotovora ◽

Quorum Sensing Inhibition

Download Full-text

Comparative Analysis of Two Classes of Quorum-Sensing Signaling Systems That Control Production of Extracellular Proteins and Secondary Metabolites in Erwinia carotovora Subspecies

Journal of Bacteriology ◽

10.1128/jb.187.23.8026-8038.2005 ◽

2005 ◽

Vol 187 (23) ◽

pp. 8026-8038 ◽

Cited By ~ 40

Author(s):

Asita Chatterjee ◽

Yaya Cui ◽

Hiroaki Hasegawa ◽

Nathan Leigh ◽

Vaishali Dixit ◽

...

Keyword(s):

Quorum Sensing ◽

Secondary Metabolites ◽

Extracellular Enzyme ◽

Erwinia Carotovora ◽

Homoserine Lactone ◽

Class Ii ◽

Extracellular Proteins ◽

Class I ◽

Mobility Shift ◽

Signaling Systems

ABSTRACT In Erwinia carotovora subspecies, N-acyl homoserine lactone (AHL) controls the expression of various traits, including extracellular enzyme/protein production and pathogenicity. We report here that E. carotovora subspecies possess two classes of quorum-sensing signaling systems defined by the nature of the major AHL analog produced as well as structural and functional characteristics of AHL synthase (AhlI) and AHL receptor (ExpR). Class I strains represented by E. carotovora subsp. atroseptica strain Eca12 and E. carotovora subsp. carotovora strains EC153 and SCC3193 produce 3-oxo-C8-HL (N-3-oxooctanoyl-l-homoserine lactone) as the major AHL analog as well as low but detectable levels of 3-oxo-C6-HL (N-3-oxohexanoyl-l-homoserine lactone). In contrast, the members of class II (i.e., E. carotovora subsp. betavasculorum strain Ecb168 and E. carotovora subsp. carotovora strains Ecc71 and SCRI193) produce 3-oxo-C6-HL as the major analog. ExpR species of both classes activate rsmA (Rsm, repressor of secondary metabolites) transcription and bind rsmA DNA. Gel mobility shift assays with maltose-binding protein (MBP)-ExpR71 and MBP-ExpR153 fusion proteins show that both bind a 20-mer sequence present in rsmA. The two ExpR functions (i.e., expR-mediated activation of rsmA expression and ExpR binding with rsmA DNA) are inhibited by AHL. The AHL effects are remarkably specific in that expR effect of EC153, a strain belonging to class I, is counteracted by 3-oxo-C8-HL but not by 3-oxo-C6-HL. Conversely, the expR effect of Ecc71, a strain belonging to class II, is neutralized by 3-oxo-C6-HL but not by 3-oxo-C8-HL. The AHL responses correlated with expR-mediated inhibition of exoprotein and secondary metabolite production.

Download Full-text

Identification of the central quorum sensing regulator of virulence in the enteric phytopathogen, Erwinia carotovora: the VirR repressor

Molecular Microbiology ◽

10.1111/j.1365-2958.2005.04939.x ◽

2006 ◽

Vol 59 (1) ◽

pp. 113-125 ◽

Cited By ~ 83

Author(s):

Tom Burr ◽

Anne M. L. Barnard ◽

Mark J. Corbett ◽

Clare L. Pemberton ◽

Natalie J. L. Simpson ◽

...

Keyword(s):

Quorum Sensing ◽

Erwinia Carotovora

Download Full-text

RsmA and the Quorum-Sensing Signal, N-[3-Oxohexanoyl]- l-Homoserine Lactone, Control the Levels of rsmB RNA in Erwinia carotovora subsp. carotovora by Affecting Its Stability

Journal of Bacteriology ◽

10.1128/jb.184.15.4089-4095.2002 ◽

2002 ◽

Vol 184 (15) ◽

pp. 4089-4095 ◽

Cited By ~ 40

Author(s):

Asita Chatterjee ◽

Yaya Cui ◽

Arun K. Chatterjee

Keyword(s):

Quorum Sensing ◽

Rna Binding ◽

Critical Role ◽

Regulatory System ◽

Erwinia Carotovora ◽

Homoserine Lactone ◽

Negative Regulator ◽

System Control ◽

Transcriptional Fusion ◽

Extracellular Protein Production

ABSTRACT RsmA (for regulator of secondary metabolism), RsmC, and rsmB RNA, the components of a posttranscriptional regulatory system, control extracellular protein production and pathogenicity in Erwinia carotovora subsp. carotovora. RsmA, an RNA binding protein, acts as a negative regulator by promoting message decay. rsmB RNA, on the other hand, acts as a positive regulator by neutralizing the effect of RsmA. RsmC modulates the levels of RsmA and rsmB RNA by positively regulating rsmA and negatively controlling rsmB. The level of rsmB RNA is substantially higher in RsmA+ bacteria than in RsmA− mutants. We show that rsmB RNA is more stable in the presence of RsmA than in its absence. RsmA does not stimulate the expression of an rsmB-lacZ transcriptional fusion; in fact, the β-galactosidase level is somewhat higher in RsmA− bacteria than in RsmA+ bacteria. We also investigated the basis for increased levels of rsmA and rsmB RNAs in the absence of the quorum-sensing signal, N-[3-oxohexanoyl]-l-homoserine lactone (OHL). The absence of OHL activates transcription of rsmA but not of rsmB. Instead, increased stability of rsmB RNA in the presence of RsmA accounts for the elevated levels of the rsmB RNA in OHL− bacteria. Mutant studies disclosed that while RsmA, OHL, and RsmC control the levels of rsmB RNA, high levels of rsmB RNA occur in the absence of RsmC or OHL only in RsmA+ bacteria, indicating a critical role for RsmA in modulating the levels of rsmB RNA. The findings reported here firmly establish that the quorum-sensing signal is channeled in E. carotovora subsp. carotovora via the rsmA-rsmB posttranscriptional regulatory system.

Download Full-text

Quorum sensing in soft-rotting Erwinia carotovora

10.32469/10355/5815 ◽

2005 ◽

Author(s):

◽

Hiroaki Hasegawa

Keyword(s):

Quorum Sensing ◽

Rna Binding ◽

Elevated Temperatures ◽

Minor Component ◽

Pectate Lyase ◽

Erwinia Carotovora ◽

Homoserine Lactone ◽

Class Ii ◽

Negative Regulator ◽

Class I

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The soft-rotting E. carotovora subspecies (ssp.) produces effectors and an array ofextra cellular enzymes, including pectate lyase (Pel), polygalacturonase (Peh), cellulase (Cell) and protease (Prt) that are known or predicted to function as virulence and pathogenicity factors. The production of these exoproteins is activated by quorum sensing (QS)signal, N-acyl homoserine lactone (AHL). At elevated temperatures, however, a majority of E. c. ssp. atroseptica (Eca), betavasculorum (Ecb) and carotovora (Ecc) strains produce much reduced amounts of AHL as well as those exoproteins, and activate the production of a global negative regulator, RsmA (Rsm = regulator of secondarymetabolites). Ecc strain EC153 is an exception in that it produces higher levels of exproteins as well as AHL at 34.5[degree sign]C than at 28[degree sign]C. Temperature-dependent production of virrulence factors by these strains correlates with overall metabolic activities and stabilities of ahlI (the gene for AHL synthase), pel-1 and peh-1 transcripts. EC153 also causes extensive maceration of celery and Chinese cabbage petioles at 34.5[degree sign]C, which contrasts with limited tissue maceration by Ecc strain Ecc71 at this temperature. Thus, overall metabolic activity, higher levels of AHL and greater mRNA stability of virulence activates transcription of rsmA. This activation of rsmA is prevented by AHL. Consequently, in the presence of AHL RsmA production occurs at a low level, triggering the production of virulence factors. These findings for the first time document regulation of an RNA-binding protien by ExpR and AHL, link quorum sensing system via posttransciptional regulation, and explain the basis for the pleiotropic effects of AHL in Ecc. This study also reports the existence of two classes of strains based on structural and functional characteristics of ExpR and AhlI in Erwinia carotovora subspecies. While class I strains produce 3-oxooctanoyl-L-homoserine lactone (3-oxo-C8-HL) as the major AHL analog and 3-oxohexanoyl homoserine lactone (3-oxo-C6-HL) as a minor component, the members of class II strains produce 3-oxo-C6-HL as the major analog. It has also been found that AHL synthase is responsible for biosynthetic specificity. ExpR species do not discriminate between rsmA genes of strains belonging to the two classes. However, specificity is conferred by AHL analogs in that 3-oxo-C8-HL neutralizes the actions of class II ExpRs whereas 3-oxo-C6HL neutalizes class I ExpRs.

Download Full-text