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Numata Y, Kikuchi Y, Sato T, Okamoto-Shibayama K, Ando Y, Miyai-Murai Y, Kokubu E, Ishihara K. Novel transcriptional regulator OxtR1 regulates potential ferrodoxin in response to oxygen stress in Treponema denticola. Anaerobe 2024; 87:102852. [PMID: 38614291 DOI: 10.1016/j.anaerobe.2024.102852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 02/26/2024] [Accepted: 04/08/2024] [Indexed: 04/15/2024]
Abstract
OBJECTIVE Treponema denticola has been strongly implicated in the pathogenesis of chronic periodontitis. Previously, we reported that the potential transcriptional regulator TDE_0259 (oxtR1) is upregulated in the bacteriocin ABC transporter gene-deficient mutant. OxtR1 may regulate genes to adapt to environmental conditions during colonization; however, the exact role of the gene in T. denticola has not been reported. Therefore, we investigated its function using an oxtR1-deficient mutant. METHODS The growth rates of the wild-type and oxtR1 mutant were monitored under anaerobic conditions; their antibacterial agent susceptibility and gene expression were assessed using a liquid dilution assay and DNA microarray, respectively. An electrophoretic mobility shift assay was performed to investigate the binding of OxtR1 to promoter regions. RESULTS The growth rate of the bacterium was accelerated by the inactivation of oxtR1, and the mutant exhibited an increased minimum inhibitory concentration against ofloxacin. We observed a relative increase in the expression of genes associated with potential ferrodoxin (TDE_0260), flavodoxin, ABC transporters, heat-shock proteins, DNA helicase, iron compounds, and lipoproteins in the mutant. OxtR1 expression increased upon oxygen exposure, and oxtR1 complementation suppressed the expression of potential ferrodoxin. Our findings also suggested that OxtR1 binds to a potential promoter region of the TDE_0259-260 operon. Moreover, the mutant showed a marginal yet significantly faster growth rate than the wild-type strain under H2O2 exposure. CONCLUSION The oxygen-sensing regulator OxtR1 plays a role in regulating the expression of a potential ferrodoxin, which may contribute to the response of T. denticola to oxygen-induced stress.
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Affiliation(s)
- Yumi Numata
- Department of Crown and Bridge Prosthodontics, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Yuichiro Kikuchi
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; Oral Health Science Center, Tokyo Dental College, 2-9-18 Kanda-Misakicho Chiyoda-ku, Tokyo 101-0061, Japan
| | - Toru Sato
- Department of Crown and Bridge Prosthodontics, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Kazuko Okamoto-Shibayama
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; Oral Health Science Center, Tokyo Dental College, 2-9-18 Kanda-Misakicho Chiyoda-ku, Tokyo 101-0061, Japan
| | - Yutaro Ando
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; Oral Health Science Center, Tokyo Dental College, 2-9-18 Kanda-Misakicho Chiyoda-ku, Tokyo 101-0061, Japan
| | - Yuri Miyai-Murai
- Department of Crown and Bridge Prosthodontics, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
| | - Eitoyo Kokubu
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; Oral Health Science Center, Tokyo Dental College, 2-9-18 Kanda-Misakicho Chiyoda-ku, Tokyo 101-0061, Japan
| | - Kazuyuki Ishihara
- Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan; Oral Health Science Center, Tokyo Dental College, 2-9-18 Kanda-Misakicho Chiyoda-ku, Tokyo 101-0061, Japan.
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Nazaret F, Alloing G, Mandon K, Frendo P. MarR Family Transcriptional Regulators and Their Roles in Plant-Interacting Bacteria. Microorganisms 2023; 11:1936. [PMID: 37630496 PMCID: PMC10458429 DOI: 10.3390/microorganisms11081936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023] Open
Abstract
The relationship between plants and associated soil microorganisms plays a major role in ecosystem functioning. Plant-bacteria interactions involve complex signaling pathways regulating various processes required by bacteria to adapt to their fluctuating environment. The establishment and maintenance of these interactions rely on the ability of the bacteria to sense and respond to biotic and abiotic environmental signals. In this context, MarR family transcriptional regulators can use these signals for transcriptional regulation, which is required to establish adapted responses. MarR-like transcriptional regulators are essential for the regulation of the specialized functions involved in plant-bacteria interactions in response to a wide range of molecules associated with the plant host. The conversion of environmental signals into changes in bacterial physiology and behavior allows the bacteria to colonize the plant and ensure a successful interaction. This review focuses on the mechanisms of plant-signal perception by MarR-like regulators, namely how they (i) allow bacteria to cope with the rhizosphere and plant endosphere, (ii) regulate the beneficial functions of Plant-Growth-Promoting Bacteria and (iii) regulate the virulence of phytopathogenic bacteria.
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Affiliation(s)
| | | | | | - Pierre Frendo
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (F.N.); (G.A.); (K.M.)
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Chen S, Hu M, Hu A, Xue Y, Wang S, Liu F, Li C, Zhou X, Zhou J. The integration host factor regulates multiple virulence pathways in bacterial pathogen Dickeya zeae MS2. MOLECULAR PLANT PATHOLOGY 2022; 23:1487-1507. [PMID: 35819797 PMCID: PMC9452768 DOI: 10.1111/mpp.13244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/12/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Dickeya zeae is an aggressive bacterial phytopathogen that infects a wide range of host plants. It has been reported that integration host factor (IHF), a nucleoid-associated protein consisting of IHFα and IHFβ subunits, regulates gene expression by influencing nucleoid structure and DNA bending. To define the role of IHF in the pathogenesis of D. zeae MS2, we deleted either and both of the IHF subunit encoding genes ihfA and ihfB, which significantly reduced the production of cell wall-degrading enzymes (CWDEs), an unknown novel phytotoxin and the virulence factor-modulating (VFM) quorum-sensing (QS) signal, cell motility, biofilm formation, and thereafter the infection ability towards both potato slices and banana seedlings. To characterize the regulatory pathways of IHF protein associated with virulence, IHF binding sites (consensus sequence 5'-WATCAANNNNTTR-3') were predicted and 272 binding sites were found throughout the genome. The expression of 110 tested genes was affected by IHF. Electrophoretic mobility shift assay (EMSA) showed direct interaction of IhfA protein with the promoters of vfmE, speA, pipR, fis, slyA, prtD, hrpL, hecB, hcp, indA, hdaA, flhD, pilT, gcpJ, arcA, arcB, and lysR. This study clarified the contribution of IHF in the pathogenic process of D. zeae by controlling the production of VFM and putrescine QS signals, phytotoxin, and indigoidine, the luxR-solo system, Fis, SlyA, and FlhD transcriptional regulators, and secretion systems from type I to type VI. Characterization of the regulatory networks of IHF in D. zeae provides a target for prevention and control of plant soft rot disease.
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Affiliation(s)
- Shanshan Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Ming Hu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Anqun Hu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Yang Xue
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Si Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Fan Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Chuhao Li
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Xiaofan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease ControlIntegrative Microbiology Research Center, South China Agricultural UniversityGuangzhouChina
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Forquet R, Jiang X, Nasser W, Hommais F, Reverchon S, Meyer S. Mapping the Complex Transcriptional Landscape of the Phytopathogenic Bacterium Dickeya dadantii. mBio 2022; 13:e0052422. [PMID: 35491820 PMCID: PMC9239193 DOI: 10.1128/mbio.00524-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 04/07/2022] [Indexed: 11/21/2022] Open
Abstract
Dickeya dadantii is a phytopathogenic bacterium that causes soft rot in a wide range of plant hosts worldwide and a model organism for studying virulence gene regulation. The present study provides a comprehensive and annotated transcriptomic map of D. dadantii obtained by a computational method combining five independent transcriptomic data sets: (i) paired-end RNA sequencing (RNA-seq) data for a precise reconstruction of the RNA landscape; (ii) DNA microarray data providing transcriptional responses to a broad variety of environmental conditions; (iii) long-read Nanopore native RNA-seq data for isoform-level transcriptome validation and determination of transcription termination sites; (iv) differential RNA sequencing (dRNA-seq) data for the precise mapping of transcription start sites; (v) in planta DNA microarray data for a comparison of gene expression profiles between in vitro experiments and the early stages of plant infection. Our results show that transcription units sometimes coincide with predicted operons but are generally longer, most of them comprising internal promoters and terminators that generate alternative transcripts of variable gene composition. We characterize the occurrence of transcriptional read-through at terminators, which might play a basal regulation role and explain the extent of transcription beyond the scale of operons. We finally highlight the presence of noncontiguous operons and excludons in the D. dadantii genome, novel genomic arrangements that might contribute to the basal coordination of transcription. The highlighted transcriptional organization may allow D. dadantii to finely adjust its gene expression program for a rapid adaptation to fast-changing environments. IMPORTANCE This is the first transcriptomic map of a Dickeya species. It may therefore significantly contribute to further progress in the field of phytopathogenicity. It is also one of the first reported applications of long-read Nanopore native RNA-seq in prokaryotes. Our findings yield insights into basal rules of coordination of transcription that might be valid for other bacteria and may raise interest in the field of microbiology in general. In particular, we demonstrate that gene expression is coordinated at the scale of transcription units rather than operons, which are larger functional genomic units capable of generating transcripts with variable gene composition for a fine-tuning of gene expression in response to environmental changes. In line with recent studies, our findings indicate that the canonical operon model is insufficient to explain the complexity of bacterial transcriptomes.
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Affiliation(s)
- Raphaël Forquet
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Xuejiao Jiang
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - William Nasser
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Florence Hommais
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Sylvie Reverchon
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Sam Meyer
- Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
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Condemine G, Le Derout B. Identification of new Dickeya dadantii virulence factors secreted by the type 2 secretion system. PLoS One 2022; 17:e0265075. [PMID: 35417462 PMCID: PMC9007343 DOI: 10.1371/journal.pone.0265075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 02/22/2022] [Indexed: 11/18/2022] Open
Abstract
Dickeya are plant pathogenic bacteria able to provoke disease on a wide range of plants. A type 2 secretion system (T2SS) named Out is necessary for Dickeya virulence. Previous studies showed that the D. dadantii T2SS secretes a wide range of plant cell wall degrading enzymes, including pectinases and a cellulase. However, the full repertoire of exoproteins it can secrete has probably not yet been identified. Secreted proteins possess a signal peptide and are first addressed to the periplasm before their recruitment by Out. T2SS-specific secretion signals remain unknown which prevents in silico identification of T2SS substrates. To identify new Out substrates, we analyzed D. dadantii transcriptome data obtained in plant infection condition and searched for genes strongly induced and encoding proteins with a signal sequence. We identified four new Out-secreted proteins: the expansin YoaJ, the putative virulence factor VirK and two proteins of the DUF 4879 family, SvfA and SvfB. We showed that SvfA and SvfB are required for full virulence of D. dadantii and that svf genes are present in a variable number of copies in other Pectobacteriaceae, up to three in D. fanghzongdai. This work opens the way to the study of the role of non-pectinolytic proteins secreted by the Out pathway in Pectobacteriaceae.
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Affiliation(s)
- Guy Condemine
- Univ Lyon, Université Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et Pathogénie, Villeurbanne, France
- * E-mail:
| | - Bastien Le Derout
- Univ Lyon, Université Lyon 1, INSA de Lyon, CNRS UMR 5240 Microbiologie Adaptation et Pathogénie, Villeurbanne, France
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Zhang J, Arif M, Shen H, Sun D, Pu X, Hu J, Lin B, Yang Q. Genomic Comparisons and Phenotypic Diversity of Dickeya zeae Strains Causing Bacterial Soft Rot of Banana in China. FRONTIERS IN PLANT SCIENCE 2022; 13:822829. [PMID: 35222482 PMCID: PMC8864124 DOI: 10.3389/fpls.2022.822829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 01/19/2022] [Indexed: 06/14/2023]
Abstract
Bacterial soft rot of banana, caused by Dickeya zeae, is spreading rapidly in important banana growing areas in China and seriously threatens banana production. In this study, we sequenced the high-quality complete genomes of three typical banana strains, MS1 (size: 4,831,702-bp; genome coverages: 538x), MS_2014 (size: 4,740,000-bp; genome coverages: 586x) and MS_2018 (size: 4,787,201-bp; genome coverages: 583x), isolated in 2009, 2014, and 2018, respectively. To determine their genomic and phenotypic diversity with respect to their hosts of origin, they were compared with other D. zeae strains, including another representative banana strain MS2 from China. The sequenced strains were similar in utilization of carbon source and chemical substrates, and general genomic features of GC content, and tRNA and rRNA regions. They were also conserved in most virulence determinants, including gene-encoding secretion systems, plant cell wall degrading enzymes, and exopolysaccharides. We further explored their genomic diversity in the predicted genomic islands (GIs). These GIs were rich in integrases and transposases, where some genomic dissimilarity was observed in the flagellar gene cluster and several secondary metabolite gene clusters. Different constituents of core biosynthetic modules were found within the bacteriocin and aryl polyene (APE) pigment gene clusters, and the strains from banana showed different phenotypes with respect to antibiosis effects and colony pigmentation. Additionally, clustered regularly interspaced short palindromic repeat (CRISPR) and prophage elements, such as type I-F and III-A CRISPR arrays and an intact prophage of MS1-P5, contributed to bacterial diversity. Phylogenetic tree analysis and genome-genome nucleotide comparison confirmed the genomic divergence among the strains isolated from banana. Considering these characteristics, MS2 and MS_2014 probably diverged later than MS1, while MS_2018 was different and more similar to foreign strains isolated from other hosts in several characteristics. Strain MS_2018 caused severe symptoms on banana varieties previously considered moderately resistant or moderately susceptible, including varieties of Cavendish (Musa AAA) and Plantain (Musa ABB). Our study of genomic and phenotypic diversity raises public attention to the risk of spreading new pathogenic variants within banana growing regions and supports development of predictive strategies for disease control.
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Affiliation(s)
- Jingxin Zhang
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Mohammad Arif
- Department of Plant and Environmental Protection Sciences, College of Tropical Agriculture and Human Resources, University of Hawai’i at Mānoa, Honolulu, HI, United States
| | - Huifang Shen
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Dayuan Sun
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Xiaoming Pu
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - John Hu
- Department of Plant and Environmental Protection Sciences, College of Tropical Agriculture and Human Resources, University of Hawai’i at Mānoa, Honolulu, HI, United States
| | - Birun Lin
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Qiyun Yang
- Key Laboratory of New Technique for Plant Protection in Guangdong, Institute of Plant Protection, Guangdong Academy of Agricultural Sciences, Guangzhou, China
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Liu F, Hu M, Zhang Z, Xue Y, Chen S, Hu A, Zhang LH, Zhou J. Dickeya Manipulates Multiple Quorum Sensing Systems to Control Virulence and Collective Behaviors. FRONTIERS IN PLANT SCIENCE 2022; 13:838125. [PMID: 35211146 PMCID: PMC8860905 DOI: 10.3389/fpls.2022.838125] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/07/2022] [Indexed: 06/12/2023]
Abstract
Soft rot Pectobacteriaceae (SRP), typical of Pectobacterium and Dickeya, are a class of Gram-negative bacterial pathogens that cause devastating diseases on a wide range of crops and ornamental plants worldwide. Quorum sensing (QS) is a cell-cell communication mechanism regulating the expression of specific genes by releasing QS signal molecules associated with cell density, in most cases, involving in the vital process of virulence and infection. In recent years, several types of QS systems have been uncovered in Dickeya pathogens to control diverse biological behaviors, especially bacterial pathogenicity and transkingdom interactions. This review depicts an integral QS regulation network of Dickeya, elaborates in detail the regulation of specific QS system on different biological functions of the pathogens and hosts, aiming at providing a systematic overview of Dickeya pathogenicity and interactions with hosts, and, finally, expects the future prospective of effectively controlling the bacterial soft rot disease caused by Dickeya by quenching the key QS signal.
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Leonard S, Villard C, Nasser W, Reverchon S, Hommais F. RNA Chaperones Hfq and ProQ Play a Key Role in the Virulence of the Plant Pathogenic Bacterium Dickeya dadantii. Front Microbiol 2021; 12:687484. [PMID: 34248909 PMCID: PMC8264596 DOI: 10.3389/fmicb.2021.687484] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 05/31/2021] [Indexed: 12/01/2022] Open
Abstract
Dickeya dadantii is an important pathogenic bacterium that infects a number of crops including potato and chicory. While extensive works have been carried out on the control of the transcription of its genes encoding the main virulence functions, little information is available on the post-transcriptional regulation of these functions. We investigated the involvement of the RNA chaperones Hfq and ProQ in the production of the main D. dadantii virulence functions. Phenotypic assays on the hfq and proQ mutants showed that inactivation of hfq resulted in a growth defect, a modified capacity for biofilm formation and strongly reduced motility, and in the production of degradative extracellular enzymes (proteases, cellulase, and pectate lyases). Accordingly, the hfq mutant failed to cause soft rot on chicory leaves. The proQ mutant had reduced resistance to osmotic stress, reduced extracellular pectate lyase activity compared to the wild-type strain, and reduced virulence on chicory leaves. Most of the phenotypes of the hfq and proQ mutants were related to the low amounts of mRNA of the corresponding virulence factors. Complementation of the double mutant hfq-proQ by each individual protein and cross-complementation of each chaperone suggested that they might exert their effects via partially overlapping but different sets of targets. Overall, it clearly appeared that the two Hfq and ProQ RNA chaperones are important regulators of pathogenicity in D. dadantii. This underscores that virulence genes are regulated post-transcriptionally by non-coding RNAs.
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Affiliation(s)
- Simon Leonard
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5240 MAP, Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Camille Villard
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5240 MAP, Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - William Nasser
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5240 MAP, Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Sylvie Reverchon
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5240 MAP, Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
| | - Florence Hommais
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5240 MAP, Microbiologie, Adaptation, Pathogénie, Villeurbanne, France
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Lecomte S, Nesme X, Franzino T, Villard C, Pivard M, Vial L, Doré J, Hommais F, Haichar FEZ. Agrobacterium fabrum C58 involved nitrate reductase NapA and antisense RNA NorR to denitrify. FEMS Microbiol Ecol 2021; 97:5989693. [PMID: 33206969 DOI: 10.1093/femsec/fiaa233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 11/16/2020] [Indexed: 01/23/2023] Open
Abstract
Agrobacterium fabrum C58 is a plant-associated bacterium that is able to denitrify under anoxic conditions. The cluster of denitrification genes harbored by this strain has been well characterized. It includes nir and nor operons encoding nitrite and nitric oxide reductases, respectively. However, the reductase involved in nitrate reduction has not yet been studied and little information is available on denitrification regulators in A. fabrum C58. In this study, we aimed to (i) characterize the nitrate reductase, (ii) determine its role in A. fabrum C58 fitness and root colonization and (ii) reveal the contribution of small RNA on denitrification regulation. By constructing a mutant strain defective for napA, we demonstrated that the reduction of nitrate to nitrite was catalyzed by the periplasmic nitrate reductase, NapA. We evidenced a positive role of NapA in A. fabrum C58 fitness and suggested that A. fabrum C58 is able to use components exuded by plant roots to respire anaerobically. Here, we showed that NorR small RNA increased the level of norCBQ mRNA and a decrease of NorR is correlated with a decrease in N2O emission. Together, our results underscore the importance of understanding the denitrification pathway at the strain level in order to develop strategies to mitigate N2O production at the microbial community level.
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Affiliation(s)
- Solène Lecomte
- Univ Lyon, UCBL, CNRS, INRA, VetAgro Sup, UMR5557 Laboratoire d'Ecologie Microbienne (LEM), F-69622 Villeurbanne Cedex, France
| | - Xavier Nesme
- Univ Lyon, UCBL, CNRS, INRA, VetAgro Sup, UMR5557 Laboratoire d'Ecologie Microbienne (LEM), F-69622 Villeurbanne Cedex, France
| | - Théophile Franzino
- Univ Lyon, UCBL, CNRS, INSA, UMR5240 Laboratoire de Microbiologie Adaptation Pathogénie (MAP), F-69622 Villeurbanne Cedex, France
| | - Camille Villard
- Univ Lyon, UCBL, CNRS, INSA, UMR5240 Laboratoire de Microbiologie Adaptation Pathogénie (MAP), F-69622 Villeurbanne Cedex, France
| | - Mariane Pivard
- Univ Lyon, UCBL, CNRS, INSERM, Centre International de Recherche en Infectiologie (CIRI), Lyon, France
| | - Ludovic Vial
- Univ Lyon, UCBL, CNRS, INRA, VetAgro Sup, UMR5557 Laboratoire d'Ecologie Microbienne (LEM), F-69622 Villeurbanne Cedex, France
| | - Jeanne Doré
- Univ Lyon, UCBL, CNRS, INRA, VetAgro Sup, UMR5557 Laboratoire d'Ecologie Microbienne (LEM), F-69622 Villeurbanne Cedex, France
| | - Florence Hommais
- Univ Lyon, UCBL, CNRS, INSA, UMR5240 Laboratoire de Microbiologie Adaptation Pathogénie (MAP), F-69622 Villeurbanne Cedex, France
| | - Feth El Zahar Haichar
- Univ Lyon, UCBL, CNRS, INRA, VetAgro Sup, UMR5557 Laboratoire d'Ecologie Microbienne (LEM), F-69622 Villeurbanne Cedex, France.,Univ Lyon, UCBL, CNRS, INSA, UMR5240 Laboratoire de Microbiologie Adaptation Pathogénie (MAP), F-69622 Villeurbanne Cedex, France
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Reverchon S, Meyer S, Forquet R, Hommais F, Muskhelishvili G, Nasser W. The nucleoid-associated protein IHF acts as a 'transcriptional domainin' protein coordinating the bacterial virulence traits with global transcription. Nucleic Acids Res 2021; 49:776-790. [PMID: 33337488 PMCID: PMC7826290 DOI: 10.1093/nar/gkaa1227] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 11/30/2020] [Accepted: 12/07/2020] [Indexed: 02/04/2023] Open
Abstract
Bacterial pathogenic growth requires a swift coordination of pathogenicity function with various kinds of environmental stress encountered in the course of host infection. Among the factors critical for bacterial adaptation are changes of DNA topology and binding effects of nucleoid-associated proteins transducing the environmental signals to the chromosome and coordinating the global transcriptional response to stress. In this study, we use the model phytopathogen Dickeya dadantii to analyse the organisation of transcription by the nucleoid-associated heterodimeric protein IHF. We inactivated the IHFα subunit of IHF thus precluding the IHFαβ heterodimer formation and determined both phenotypic effects of ihfA mutation on D. dadantii virulence and the transcriptional response under various conditions of growth. We show that ihfA mutation reorganises the genomic expression by modulating the distribution of chromosomal DNA supercoils at different length scales, thus affecting many virulence genes involved in both symptomatic and asymptomatic phases of infection, including those required for pectin catabolism. Altogether, we propose that IHF heterodimer is a 'transcriptional domainin' protein, the lack of which impairs the spatiotemporal organisation of transcriptional stress-response domains harbouring various virulence traits, thus abrogating the pathogenicity of D. dadantii.
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Affiliation(s)
- Sylvie Reverchon
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Sam Meyer
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Raphaël Forquet
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Florence Hommais
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, F-69622, France
| | - Georgi Muskhelishvili
- Agricultural University of Georgia, School of Natural Sciences, 0159 Tbilisi, Georgia
| | - William Nasser
- Univ Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, F-69622, France
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11
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Quorum Sensing Regulation in Phytopathogenic Bacteria. Microorganisms 2021; 9:microorganisms9020239. [PMID: 33498890 PMCID: PMC7912708 DOI: 10.3390/microorganisms9020239] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 11/17/2022] Open
Abstract
Quorum sensing is a type of chemical communication by which bacterial populations control expression of their genes in a coordinated manner. This regulatory mechanism is commonly used by pathogens to control the expression of genes encoding virulence factors and that of genes involved in the bacterial adaptation to variations in environmental conditions. In phytopathogenic bacteria, several mechanisms of quorum sensing have been characterized. In this review, we describe the different quorum sensing systems present in phytopathogenic bacteria, such as those using the signal molecules named N-acyl-homoserine lactone (AHL), diffusible signal factor (DSF), and the unknown signal molecule of the virulence factor modulating (VFM) system. We focus on studies performed on phytopathogenic bacteria of major importance, including Pseudomonas, Ralstonia, Agrobacterium, Xanthomonas, Erwinia, Xylella,Dickeya, and Pectobacterium spp. For each system, we present the mechanism of regulation, the functions targeted by the quorum sensing system, and the mechanisms by which quorum sensing is regulated.
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12
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Yuan X, Yu M, Yang CH. Innovation and Application of the Type III Secretion System Inhibitors in Plant Pathogenic Bacteria. Microorganisms 2020; 8:microorganisms8121956. [PMID: 33317075 PMCID: PMC7764658 DOI: 10.3390/microorganisms8121956] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/05/2020] [Accepted: 12/07/2020] [Indexed: 12/16/2022] Open
Abstract
Many Gram-negative pathogenic bacteria rely on a functional type III secretion system (T3SS), which injects multiple effector proteins into eukaryotic host cells, for their pathogenicity. Genetic studies conducted in different host-microbe pathosystems often revealed a sophisticated regulatory mechanism of their T3SSs, suggesting that the expression of T3SS is tightly controlled and constantly monitored by bacteria in response to the ever-changing host environment. Therefore, it is critical to understand the regulation of T3SS in pathogenic bacteria for successful disease management. This review focuses on a model plant pathogen, Dickeyadadantii, and summarizes the current knowledge of its T3SS regulation. We highlight the roles of several T3SS regulators that were recently discovered, including the transcriptional regulators: FlhDC, RpoS, and SlyA; the post-transcriptional regulators: PNPase, Hfq with its dependent sRNA ArcZ, and the RsmA/B system; and the bacterial second messenger cyclic-di-GMP (c-di-GMP). Homologs of these regulatory components have also been characterized in almost all major bacterial plant pathogens like Erwiniaamylovora, Pseudomonassyringae, Pectobacterium spp., Xanthomonas spp., and Ralstonia spp. The second half of this review shifts focus to an in-depth discussion of the innovation and development of T3SS inhibitors, small molecules that inhibit T3SSs, in the field of plant pathology. This includes T3SS inhibitors that are derived from plant phenolic compounds, plant coumarins, and salicylidene acylhydrazides. We also discuss their modes of action in bacteria and application for controlling plant diseases.
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Affiliation(s)
- Xiaochen Yuan
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA;
| | - Manda Yu
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
- Correspondence: (M.Y.); (C.-H.Y.)
| | - Ching-Hong Yang
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
- Correspondence: (M.Y.); (C.-H.Y.)
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Genomic divergence between Dickeya zeae strain EC2 isolated from rice and previously identified strains, suggests a different rice foot rot strain. PLoS One 2020; 15:e0240908. [PMID: 33079956 PMCID: PMC7575072 DOI: 10.1371/journal.pone.0240908] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 10/06/2020] [Indexed: 11/19/2022] Open
Abstract
Rice foot rot caused by Dickeya zeae is an important bacterial disease of rice worldwide. In this study, we identified a new strain EC2 from rice in Guangdong province, China. This strain differed from the previously identified strain from rice in its biochemical characteristics, pathogenicity, and genomic constituents. To explore genomic discrepancies between EC2 and previously identified strains from rice, a complete genome sequence of EC2 was obtained and used for comparative genomic analyses. The complete genome sequence of EC2 is 4,575,125 bp in length. EC2 was phylogenetically closest to previously identified Dickeya strains from rice, but not within their subgroup. In terms of secretion systems, genomic comparisons revealed that EC2 harbored only type I (T1SS), typeⅡ (T2SS), and type VI (T6SS) secretion systems. The flagella cluster of this strain possessed specific genomic characteristics like other D. zeae strains from Guangdong and from rice; within this locus, the genetic diversity among strains from rice was much lower than that of within strains from non-rice hosts. Unlike other strains from rice, EC2 lost the zeamine cluster, but retained the clustered regularly interspaced short palindromic repeats-1 (CRISPR-1) array. Compared to the other D. zeae strains containing both exopolysaccharide (EPS) and capsular polysaccharide (CPS) clusters, EC2 harbored only the CPS cluster, while the other strains from rice carried only the EPS cluster. Furthermore, we found strain MS1 from banana, carrying both EPS and CPS clusters, produced significantly more EPS than the strains from rice, and exhibited different biofilm-associated phenotypes. Comparative genomics analyses suggest EC2 likely evolved through a pathway different from the other D. zeae strains from rice, producing a new type of rice foot rot pathogen. These findings emphasize the emergence of a new type of D. zeae strain causing rice foot rot, an essential step in the early prevention of this rice bacterial disease.
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Multistep Metabolic Engineering of Bacillus licheniformis To Improve Pulcherriminic Acid Production. Appl Environ Microbiol 2020; 86:AEM.03041-19. [PMID: 32111589 DOI: 10.1128/aem.03041-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 02/11/2020] [Indexed: 11/20/2022] Open
Abstract
The cyclodipeptide pulcherriminic acid, produced by Bacillus licheniformis, is derived from cyclo(l-Leu-l-Leu) and possesses excellent antibacterial activities. In this study, we achieved the high-level production of pulcherriminic acid via multistep metabolic engineering of B. licheniformis DWc9n*. First, we increased leucine (Leu) supply by overexpressing the ilvBHC-leuABCD operon and ilvD, involved in Leu biosynthesis, to obtain strain W1, and the engineered strain W2 was further attained by the deletion of gene bkdAB, encoding a branched-chain α-keto acid dehydrogenase in W1. As a result, the intracellular Leu content and pulcherriminic acid yield of W2 reached 147.4 mg/g DCW (dry cell weight) and 189.9 mg/liter, which were 227.6% and 48.9% higher than those of DWc9n*, respectively. Second, strain W3 was constructed through overexpressing the leucyl-tRNA synthase gene leuS in W2, and it produced 367.7 mg/liter pulcherriminic acid. Third, the original promoter of the pulcherriminic acid synthetase cluster yvmC-cypX in W3 was replaced with a proven strong promoter, PbacA, to produce the strain W4, and its pulcherriminic acid yield was increased to 507.4 mg/liter. Finally, pulcherriminic acid secretion was strengthened via overexpressing the transporter gene yvmA in W4, resulting in the W4/pHY-yvmA strain, which yielded 556.1 mg/liter pulcherriminic acid, increased by 337.8% compared to DWc9n*, which is currently the highest pulcherriminic acid yield to the best of our knowledge. Taken together, we provided an efficient strategy for enhancing pulcherriminic acid production, which could apply to the high-level production of other cyclodipeptides.IMPORTANCE Pulcherriminic acid is a cyclodipeptide derived from cyclo(l-Leu-l-Leu), which shares the same iron chelation group with hydroxamate sidephores. Generally, pulcherriminic acid-producing strains could be the perfect candidates for antibacterial and anti-plant-pathogenic fungal agents. In this study, we obtained the promising W4/pHY-yvmA pulcherriminic acid-producing strain via a multistep metabolic modification. The engineered W4/pHY-yvmA strain is able to achieve 556.1 mg/liter pulcherriminic acid production, which is the highest yield so far to the best of our knowledge.
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Horizontally Acquired Quorum-Sensing Regulators Recruited by the PhoP Regulatory Network Expand the Host Adaptation Repertoire in the Phytopathogen Pectobacterium brasiliense. mSystems 2020; 5:5/1/e00650-19. [PMID: 31992632 PMCID: PMC6989131 DOI: 10.1128/msystems.00650-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
In this study, we examine the impact of transcriptional network rearrangements driven by horizontal gene acquisition in PhoP and SlyA regulons using as a case study a phytopathosystem comprised of potato tubers and the soft-rot pathogen Pectobacterium brasiliense 1692 (Pb1692). Genome simulations and statistical analyses uncovered the tendency of PhoP and SlyA networks to mobilize lineage-specific traits predicted as horizontal gene transfer at late infection, highlighting the prominence of regulatory network rearrangements in this stage of infection. The evidence further supports the circumscription of two horizontally acquired quorum-sensing regulators (carR and expR1) by the PhoP network. By recruiting carR and expR1, the PhoP network also impacts certain host adaptation- and bacterial competition-related systems, seemingly in a quorum sensing-dependent manner, such as the type VI secretion system, carbapenem biosynthesis, and plant cell wall-degrading enzymes (PCWDE) like cellulases and pectate lyases. Conversely, polygalacturonases and the type III secretion system (T3SS) exhibit a transcriptional pattern that suggests quorum-sensing-independent regulation by the PhoP network. This includes an uncharacterized novel phage-related gene family within the T3SS gene cluster that has been recently acquired by two Pectobacterium species. The evidence further suggests a PhoP-dependent regulation of carbapenem- and PCWDE-encoding genes based on the synthesized products' optimum pH. The PhoP network also controls slyA expression in planta, which seems to impact carbohydrate metabolism regulation, especially at early infection, when 76.2% of the SlyA-regulated genes from that category also require PhoP to achieve normal expression levels.IMPORTANCE Exchanging genetic material through horizontal transfer is a critical mechanism that drives bacteria to efficiently adapt to host defenses. In this report, we demonstrate that a specific plant-pathogenic species (from the Pectobacterium genus) successfully integrated a population density-based behavior system (quorum sensing) acquired through horizontal transfer into a resident stress-response gene regulatory network controlled by the PhoP protein. Evidence found here underscores that subsets of bacterial weaponry critical for colonization, typically known to respond to quorum sensing, are also controlled by PhoP. Some of these traits include different types of enzymes that can efficiently break down plant cell walls depending on the environmental acidity level. Thus, we hypothesize that PhoP's ability to elicit regulatory responses based on acidity and nutrient availability fluctuations has strongly impacted the fixation of its regulatory connection with quorum sensing. In addition, another global gene regulator, known as SlyA, was found under the PhoP regulatory network. The SlyA regulator controls a series of carbohydrate metabolism-related traits, which also seem to be regulated by PhoP. By centralizing quorum sensing and slyA under PhoP scrutiny, Pectobacterium cells added an advantageous layer of control over those two networks that potentially enhances colonization efficiency.
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Sumi S, Suzuki Y, Matsuki T, Yamamoto T, Tsuruta Y, Mise K, Kawamura T, Ito Y, Shimada Y, Watanabe E, Watanabe S, Toriyabe M, Takano Shiratori H, Ueda K, Takano H. Light-inducible carotenoid production controlled by a MarR-type regulator in Corynebacterium glutamicum. Sci Rep 2019; 9:13136. [PMID: 31511549 PMCID: PMC6739363 DOI: 10.1038/s41598-019-49384-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 08/23/2019] [Indexed: 01/21/2023] Open
Abstract
Carotenoid production in some non-phototropic bacteria occurs in a light-dependent manner to protect cells from photo-oxidants. Knowledge regarding the transcriptional regulator involved in the light-dependent production of carotenoids of non-phototrophic bacteria has been mainly confined to coenzyme B12-based photo-sensitive regulator CarH/LitR family proteins belonging to a MerR family transcriptional regulator. In this study, we found that bacteria belonging to Micrococcales and Corynebacteriales exhibit light-dependent carotenoid-like pigment production including an amino acid-producer Corynebacterium glutamicum AJ1511. CrtR is a putative MarR family transcriptional regulator located in the divergent region of a carotenoid biosynthesis gene cluster in the genome of those bacteria. A null mutant for crtR of C. glutamicum AJ1511 exhibited constitutive production of carotenoids independent of light. A complemented strain of the crtR mutant produced carotenoids in a light-dependent manner. Transcriptional analysis revealed that the expression of carotenoid biosynthesis genes is regulated in a light-dependent manner in the wild type, while the transcription was upregulated in the crtR mutant irrespective of light. In vitro experiments demonstrated that a recombinant CrtR protein binds to the specific sequences within the intergenic region of crtR and crtE, which corresponds to −58 to −7 for crtE, and +26 to −28 for crtR with respect to the transcriptional start site, and serves as a repressor for crtE transcription directed by RNA polymerase containing SigA. Taken together, the results indicate that CrtR light-dependently controls the expression of the carotenoid gene cluster in C. glutamicum and probably closely related Actinobacteria.
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Affiliation(s)
- Satoru Sumi
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Yuto Suzuki
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Tetsuro Matsuki
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Takahiro Yamamoto
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Yudai Tsuruta
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Kou Mise
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Takuya Kawamura
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Yusuke Ito
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Yuka Shimada
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Erika Watanabe
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Shoko Watanabe
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Minami Toriyabe
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Hatsumi Takano Shiratori
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Kenji Ueda
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan
| | - Hideaki Takano
- Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, 252-0880, Japan.
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17
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Martis B S, Forquet R, Reverchon S, Nasser W, Meyer S. DNA Supercoiling: an Ancestral Regulator of Gene Expression in Pathogenic Bacteria? Comput Struct Biotechnol J 2019; 17:1047-1055. [PMID: 31452857 PMCID: PMC6700405 DOI: 10.1016/j.csbj.2019.07.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/28/2022] Open
Abstract
DNA supercoiling acts as a global and ancestral regulator of bacterial gene expression. In this review, we advocate that it plays a pivotal role in host-pathogen interactions by transducing environmental signals to the bacterial chromosome and coordinating its transcriptional response. We present available evidence that DNA supercoiling is modulated by environmental stress conditions relevant to the infection process according to ancestral mechanisms, in zoopathogens as well as phytopathogens. We review the results of transcriptomics studies obtained in widely distant bacterial species, showing that such structural transitions of the chromosome are associated to a complex transcriptional response affecting a large fraction of the genome. Mechanisms and computational models of the transcriptional regulation by DNA supercoiling are then discussed, involving both basal interactions of RNA Polymerase with promoter DNA, and more specific interactions with regulatory proteins. A final part is specifically focused on the regulation of virulence genes within pathogenicity islands of several pathogenic bacterial species.
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Affiliation(s)
- Shiny Martis B
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Raphaël Forquet
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Sylvie Reverchon
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - William Nasser
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
| | - Sam Meyer
- Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, CNRS UMR5240, Laboratoire de Microbiologie, Adaptation et Pathogénie, 11 avenue Jean Capelle, 69621 Villeurbanne, France
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Deochand DK, Pande A, Meariman JK, Grove A. Redox Sensing by PecS from the Plant Pathogen Pectobacterium atrosepticum and Its Effect on Gene Expression and the Conformation of PecS-Bound Promoter DNA. Biochemistry 2019; 58:2564-2575. [PMID: 31046241 DOI: 10.1021/acs.biochem.9b00288] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The plant pathogen Pectobacterium atrosepticum encounters a stressful environment when it colonizes the plant apoplast. Chief among the stressors are the reactive oxygen species (ROS) that are produced by the host as a first line of defense. Bacterial transcription factors in turn use these signals as cues to upregulate expression of virulence-associated genes. We have previously shown that the transcription factor PecS from P. atrosepticum binds the promoters that drive expression of pecS and pecM, which encodes an efflux pump, to repress gene expression. We show here that addition of oxidant relieves repression in vivo and in vitro. While reduced PecS distorts promoter DNA on binding, oxidized PecS does not, as evidenced by DNaseI footprinting. PecS oxidation is reversible, as shown by an oxidant-dependent quenching of the intrinsic tryptophan fluorescence that is completely reversed upon addition of a reducing agent. Cysteine 45 positioned at the PecS dimer interface is the redox sensor. Reduced PecS-C45A causes less DNA distortion on binding compared to wild-type PecS; addition of an oxidant has no effect on binding, and PecS-C45A cannot repress gene expression. Our data suggest that reduced PecS distorts its cognate DNA on binding, perhaps inducing a conformation in which promoter elements are suboptimally aligned for RNA polymerase binding, resulting in transcriptional repression. In contrast, oxidized PecS binds promoter DNA such that RNA polymerase may successfully compete with PecS for binding, allowing gene expression. This mode of regulation would facilitate induction of the PecS regulon when the bacteria encounter host-derived ROS in the plant apoplast.
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Affiliation(s)
- Dinesh K Deochand
- Department of Biological Sciences , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Anuja Pande
- Department of Biological Sciences , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Jacob K Meariman
- Department of Biological Sciences , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
| | - Anne Grove
- Department of Biological Sciences , Louisiana State University , Baton Rouge , Louisiana 70803 , United States
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MarR Family Transcription Factors from Burkholderia Species: Hidden Clues to Control of Virulence-Associated Genes. Microbiol Mol Biol Rev 2018; 83:83/1/e00039-18. [PMID: 30487164 DOI: 10.1128/mmbr.00039-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Species within the genus Burkholderia exhibit remarkable phenotypic diversity. Genomic plasticity, including genome reduction and horizontal gene transfer, has been correlated with virulence traits in several species. However, the conservation of virulence genes in species otherwise considered to have limited potential for infection suggests that phenotypic diversity may not be explained solely on the basis of genetic diversity. Instead, differential organization and control of gene regulatory networks may underlie many phenotypic differences. In this review, we evaluate how regulation of gene expression by members of the multiple antibiotic resistance regulator (MarR) family of transcription factors may contribute to shaping the physiological diversity of Burkholderia species, with a focus on the clinically relevant human pathogens. All Burkholderia species encode a relatively large number of MarR proteins, a feature common to bacteria that must respond to environmental changes such as those associated with host invasion. However, evolution of gene regulatory networks has likely resulted in orthologous transcription factors controlling disparate sets of genes. Adaptation to, and survival in, diverse habitats, including a human or plant host, is key to the success of Burkholderia species as (opportunistic) pathogens, and recent reports suggest that control of virulence-associated genes by MarR proteins features prominently among the survival strategies employed by these species. We suggest that identification of MarR regulons will contribute significantly to clarification of virulence determinants and phenotypic diversity.
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Golanowska M, Potrykus M, Motyka-Pomagruk A, Kabza M, Bacci G, Galardini M, Bazzicalupo M, Makalowska I, Smalla K, Mengoni A, Hugouvieux-Cotte-Pattat N, Lojkowska E. Comparison of Highly and Weakly Virulent Dickeya solani Strains, With a View on the Pangenome and Panregulon of This Species. Front Microbiol 2018; 9:1940. [PMID: 30233505 PMCID: PMC6127512 DOI: 10.3389/fmicb.2018.01940] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 07/31/2018] [Indexed: 11/30/2022] Open
Abstract
Bacteria belonging to the genera Dickeya and Pectobacterium are responsible for significant economic losses in a wide variety of crops and ornamentals. During last years, increasing losses in potato production have been attributed to the appearance of Dickeya solani. The D. solani strains investigated so far share genetic homogeneity, although different virulence levels were observed among strains of various origins. The purpose of this study was to investigate the genetic traits possibly related to the diverse virulence levels by means of comparative genomics. First, we developed a new genome assembly pipeline which allowed us to complete the D. solani genomes. Four de novo sequenced and ten publicly available genomes were used to identify the structure of the D. solani pangenome, in which 74.8 and 25.2% of genes were grouped into the core and dispensable genome, respectively. For D. solani panregulon analysis, we performed a binding site prediction for four transcription factors, namely CRP, KdgR, PecS and Fur, to detect the regulons of these virulence regulators. Most of the D. solani potential virulence factors were predicted to belong to the accessory regulons of CRP, KdgR, and PecS. Thus, some differences in gene expression could exist between D. solani strains. The comparison between a highly and a low virulent strain, IFB0099 and IFB0223, respectively, disclosed only small differences between their genomes but significant differences in the production of virulence factors like pectinases, cellulases and proteases, and in their mobility. The D. solani strains also diverge in the number and size of prophages present in their genomes. Another relevant difference is the disruption of the adhesin gene fhaB2 in the highly virulent strain. Strain IFB0223, which has a complete adhesin gene, is less mobile and less aggressive than IFB0099. This suggests that in this case, mobility rather than adherence is needed in order to trigger disease symptoms. This study highlights the utility of comparative genomics in predicting D. solani traits involved in the aggressiveness of this emerging plant pathogen.
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Affiliation(s)
- Malgorzata Golanowska
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Marta Potrykus
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Agata Motyka-Pomagruk
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Michal Kabza
- Department of Integrative Genomics, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
| | - Giovanni Bacci
- Department of Biology, University of Florence, Florence, Italy
| | - Marco Galardini
- EMBL, EBI, Wellcome Trust Genome Campus, Cambridge, United Kingdom
| | | | - Izabela Makalowska
- Department of Integrative Genomics, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
| | - Kornelia Smalla
- Department of Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut - Federal Research Centre for Cultivated Plants, Braunschweig, Germany
| | - Alessio Mengoni
- Department of Biology, University of Florence, Florence, Italy
| | - Nicole Hugouvieux-Cotte-Pattat
- UMR5240 Microbiologie Adaptation et Pathogénie, Univ Lyon, CNRS, Univ Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France
| | - Ewa Lojkowska
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
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Regulation of the Synthesis and Secretion of the Iron Chelator Cyclodipeptide Pulcherriminic Acid in Bacillus licheniformis. Appl Environ Microbiol 2018; 84:AEM.00262-18. [PMID: 29703732 DOI: 10.1128/aem.00262-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 04/11/2018] [Indexed: 01/27/2023] Open
Abstract
The cyclodipeptide pulcherriminic acid synthesized by Bacillus licheniformis is an iron chelator that antagonizes certain pathogens by removing iron from the environment. But since the insoluble iron-pulcherriminic acid complex cannot act as an iron carrier as siderophores do, excessive synthesized pulcherriminic acid causes iron starvation for the producer cells. At present, the regulation of pulcherriminic acid synthesis and the mechanism by which B. licheniformis strikes a balance between biocontrol and self-protection from excessive iron removal remain unclear. This study provides insights into the regulatory network and explains the mechanism of pulcherriminic acid biosynthesis. The yvmC-cypX synthetic gene cluster was directly negatively regulated by three regulators: AbrB, YvnA, and YvmB. Within the regulatory network, YvnA expression was repressed not only by AbrB but also by iron-limiting environments, while YvmB expression was repressed by YvnA. The transporter gene yvmA is repressed by YvmB and is required for pulcherriminic acid secretion. The biosynthesis window is determined by the combined concentration of the three regulators in an iron-rich environment. Under iron-limiting conditions, cells close the pulcherriminic acid synthesis pathway by downregulating YvnA expression.IMPORTANCE The cyclodipeptides are widespread in nature and exhibit a broad variety of biological and pharmacological activities. The cyclodipeptide scaffold is synthesized by nonribosomal peptide synthetases (NRPSs) and cyclodipeptide synthases (CDPSs). At present, it is clear that CDPSs use aminoacyl tRNAs as substrates to synthesize the two peptide bonds, and the pulcherriminic acid synthase YvmC is a member of the eight identified CDPSs. However, little is known about the regulation of cyclodipeptide synthesis and secretion. In this study, we show that AbrB, which is considered to be the main regulator of NRPS-dependent pathways, is also involved in the regulation of CDPS genes. However, AbrB is not the decisive factor for pulcherriminic acid synthesis, as the expression of YvnA determines the fate of pulcherriminic acid synthesis. With this information on how CDPS gene transcription is regulated, a clearer understanding of cyclodipeptide synthesis can be developed for B. licheniformis Similar approaches may be used to augment our knowledge on CDPSs in other bacteria.
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Fan JR, Zhang HX, Mu YG, Zheng QC. Studying the recognition mechanism of TcaR and ssDNA using molecular dynamic simulations. J Mol Graph Model 2018; 80:67-75. [DOI: 10.1016/j.jmgm.2017.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 12/01/2017] [Accepted: 12/01/2017] [Indexed: 10/18/2022]
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Pédron J, Chapelle E, Alunni B, Van Gijsegem F. Transcriptome analysis of the Dickeya dadantii PecS regulon during the early stages of interaction with Arabidopsis thaliana. MOLECULAR PLANT PATHOLOGY 2018; 19:647-663. [PMID: 28295994 PMCID: PMC6638149 DOI: 10.1111/mpp.12549] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 02/21/2017] [Accepted: 03/13/2017] [Indexed: 05/10/2023]
Abstract
PecS is one of the major global regulators controlling the virulence of Dickeya dadantii, a broad-host-range phytopathogenic bacterium causing soft rot on several plant families. To define the PecS regulon during plant colonization, we analysed the global transcriptome profiles in wild-type and pecS mutant strains during the early colonization of the leaf surfaces and in leaf tissue just before the onset of symptoms, and found that the PecS regulon consists of more than 600 genes. About one-half of these genes are down-regulated in the pecS mutant; therefore, PecS has both positive and negative regulatory roles that may be direct or indirect. Indeed, PecS also controls the regulation of a few dozen regulatory genes, demonstrating that this global regulator is at or near the top of a major regulatory cascade governing adaptation to growth in planta. Notably, PecS acts mainly at the very beginning of infection, not only to prevent virulence gene induction, but also playing an active role in the adaptation of the bacterium to the epiphytic habitat. Comparison of the patterns of gene expression inside leaf tissues and during early colonization of leaf surfaces in the wild-type bacterium revealed 637 genes modulated between these two environments. More than 40% of these modulated genes are part of the PecS regulon, emphasizing the prominent role of PecS during plant colonization.
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Affiliation(s)
- Jacques Pédron
- Interactions Plantes Pathogènes, AgroParisTech, INRA, UPMC Université Paris 06, Paris, 75005, France
- iEES (Institut d'Ecologie et des Sciences de l'Environnement de Paris), Sorbonne Universités, UPMC Université Paris 06, Diderot Université Paris 07, UPEC Université Paris 12, CNRS, INRA, IRD, Paris, 75005, France
| | - Emilie Chapelle
- Interactions Plantes Pathogènes, AgroParisTech, INRA, UPMC Université Paris 06, Paris, 75005, France
| | - Benoît Alunni
- Interactions Plantes Pathogènes, AgroParisTech, INRA, UPMC Université Paris 06, Paris, 75005, France
- Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Universite Paris-Sud/CEA, Gif-sur-Yvette, 91198, France
| | - Frédérique Van Gijsegem
- Interactions Plantes Pathogènes, AgroParisTech, INRA, UPMC Université Paris 06, Paris, 75005, France
- iEES (Institut d'Ecologie et des Sciences de l'Environnement de Paris), Sorbonne Universités, UPMC Université Paris 06, Diderot Université Paris 07, UPEC Université Paris 12, CNRS, INRA, IRD, Paris, 75005, France
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Sivapragasam S, Deochand DK, Meariman JK, Grove A. The Stringent Response Induced by Phosphate Limitation Promotes Purine Salvage in Agrobacterium fabrum. Biochemistry 2017; 56:5831-5843. [DOI: 10.1021/acs.biochem.7b00844] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Smitha Sivapragasam
- Department of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Dinesh K. Deochand
- Department of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Jacob K. Meariman
- Department of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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Leonard S, Hommais F, Nasser W, Reverchon S. Plant-phytopathogen interactions: bacterial responses to environmental and plant stimuli. Environ Microbiol 2017; 19:1689-1716. [DOI: 10.1111/1462-2920.13611] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 11/09/2016] [Accepted: 11/16/2016] [Indexed: 01/06/2023]
Affiliation(s)
- Simon Leonard
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - Florence Hommais
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - William Nasser
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - Sylvie Reverchon
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
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Genetic Modulation of c-di-GMP Turnover Affects Multiple Virulence Traits and Bacterial Virulence in Rice Pathogen Dickeya zeae. PLoS One 2016; 11:e0165979. [PMID: 27855163 PMCID: PMC5113947 DOI: 10.1371/journal.pone.0165979] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/20/2016] [Indexed: 11/19/2022] Open
Abstract
The frequent outbreaks of rice foot rot disease caused by Dickeya zeae have become a significant concern in rice planting regions and countries, but the regulatory mechanisms that govern the virulence of this important pathogen remain vague. Given that the second messenger cyclic di-GMP (c-di-GMP) is associated with modulation of various virulence-related traits in various microorganisms, here we set to investigate the role of the genes encoding c-di-GMP metabolism in the regulation of the bacterial physiology and virulence by construction all in-frame deletion mutants targeting the annotated c-di-GMP turnover genes in D. zeae strain EC1. Phenotype analyses identified individual mutants showing altered production of exoenzymes and phytotoxins, biofilm formation and bacterial motilities. The results provide useful clues and a valuable toolkit for further characterization and dissection of the regulatory complex that modulates the pathogenesis and persistence of this important bacterial pathogen.
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Essential Genes for In Vitro Growth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing. Appl Environ Microbiol 2016; 82:6664-6671. [PMID: 27590816 PMCID: PMC5086560 DOI: 10.1128/aem.02281-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 08/31/2016] [Indexed: 01/04/2023] Open
Abstract
The interior of plants contains microorganisms (referred to as endophytes) that are distinct from those present at the root surface or in the surrounding soil. Herbaspirillum seropedicae strain SmR1, belonging to the betaproteobacteria, is an endophyte that colonizes crops, including rice, maize, sugarcane, and sorghum. Different approaches have revealed genes and pathways regulated during the interactions of H. seropedicae with its plant hosts. However, functional genomic analysis of transposon (Tn) mutants has been hampered by the lack of genetic tools. Here we successfully employed a combination of in vivo high-density mariner Tn mutagenesis and targeted Tn insertion site sequencing (Tn-seq) in H. seropedicae SmR1. The analysis of multiple gene-saturating Tn libraries revealed that 395 genes are essential for the growth of H. seropedicae SmR1 in tryptone-yeast extract medium. A comparative analysis with the Database of Essential Genes (DEG) showed that 25 genes are uniquely essential in H. seropedicae SmR1. The Tn mutagenesis protocol developed and the gene-saturating Tn libraries generated will facilitate elucidation of the genetic mechanisms of the H. seropedicae endophytic lifestyle. IMPORTANCE A focal point in the study of endophytes is the development of effective biofertilizers that could help to reduce the input of agrochemicals in croplands. Besides the ability to promote plant growth, a good biofertilizer should be successful in colonizing its host and competing against the native microbiota. By using a systematic Tn-based gene-inactivation strategy and massively parallel sequencing of Tn insertion sites (Tn-seq), it is possible to study the fitness of thousands of Tn mutants in a single experiment. We have applied the combination of these techniques to the plant-growth-promoting endophyte Herbaspirillum seropedicae SmR1. The Tn mutant libraries generated will enable studies into the genetic mechanisms of H. seropedicae-plant interactions. The approach that we have taken is applicable to other plant-interacting bacteria.
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Deochand DK, Meariman JK, Grove A. pH-Dependent DNA Distortion and Repression of Gene Expression by Pectobacterium atrosepticum PecS. ACS Chem Biol 2016; 11:2049-56. [PMID: 27213700 DOI: 10.1021/acschembio.6b00168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Transcriptional activity is exquisitely sensitive to changes in promoter DNA topology. Transcription factors may therefore control gene activity by modulating the relative positioning of -10 and -35 promoter elements. The plant pathogen Pectobacterium atrosepticum, which causes soft rot in potatoes, must alter gene expression patterns to ensure growth in planta. In the related soft-rot enterobacterium Dickeya dadantii, PecS functions as a master regulator of virulence gene expression. Here, we report that P. atrosepticum PecS controls gene activity by altering promoter DNA topology in response to pH. While PecS binds the pecS promoter with high affinity regardless of pH, it induces significant DNA distortion only at neutral pH, the pH at which the pecS promoter is repressed in vivo. At pH ∼8, DNA distortions are attenuated, and PecS no longer represses the pecS promoter. A specific histidine (H142) located in a crevice between the dimerization- and DNA-binding regions is required for pH-dependent changes in DNA distortion and repression of gene activity, and mutation of this histidine renders the mutant protein incapable of repressing the pecS promoter. We propose that protonated PecS induces a DNA conformation at neutral pH in which -10 and -35 promoter elements are suboptimally positioned for RNA polymerase binding; on deprotonation of PecS, binding is no longer associated with significant changes in DNA conformation, allowing gene expression. We suggest that this mode of gene regulation leads to differential expression of the PecS regulon in response to alkalinization of the plant apoplast.
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Affiliation(s)
- Dinesh K. Deochand
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Jacob K. Meariman
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department
of Biological
Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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Hugouvieux-Cotte-Pattat N. Metabolism and Virulence Strategies in Dickeya-Host Interactions. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 142:93-129. [PMID: 27571693 DOI: 10.1016/bs.pmbts.2016.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Dickeya, a genus of the Enterobacteriaceae family, all cause plant diseases. They are aggressive necrotrophs that have both a wide geographic distribution and a wide host range. As a plant pathogen, Dickeya has had to adapt to a vegetarian diet. Plants constitute a large storage of carbohydrates; they contain substantial amounts of soluble sugars and the plant cell wall is composed of long polysaccharides. Metabolic functions used by Dickeya in order to multiply during infection are essential aspects of pathogenesis. Dickeya is able to catabolize a large range of oligosaccharides and glycosides of plant origin. Glucose, fructose, and sucrose are all efficiently metabolized by the bacteria. To avoid the formation of acidic products, their final catabolism involves the butanediol pathway, a nonacidifying fermentative pathway. The assimilation of plant polysaccharides necessitates their prior cleavage into oligomers. Notably, the Dickeya virulence strategy is based on its capacity to dissociate the plant cell wall and, for this, the bacteria secrete an extensive set of polysaccharide degrading enzymes, composed mostly of pectinases. Since pectic polymers have a major role in plant tissue cohesion, pectinase action results in plant rot. The pectate lyases secreted by Dickeya play a double role as virulence factors and as nutrient providers. This dual function implies that the pel gene expression is regulated by both metabolic and virulence regulators. The control of sugar assimilation by specific or global regulators enables Dickeya to link its nutritional status to virulence, a coupling that optimizes the different phases of infection.
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Affiliation(s)
- N Hugouvieux-Cotte-Pattat
- Microbiology Adaptation and Pathogenesis, CNRS, University of Lyon, University Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France.
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Reverchon S, Muskhelisvili G, Nasser W. Virulence Program of a Bacterial Plant Pathogen: The Dickeya Model. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 142:51-92. [PMID: 27571692 DOI: 10.1016/bs.pmbts.2016.05.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The pectinolytic Dickeya spp. are Gram-negative bacteria causing severe disease in a wide range of plant species. Although the Dickeya genus was initially restricted to tropical and subtropical areas, two Dickeya species (D. dianthicola and D. solani) emerged recently in potato cultures in Europe. Soft-rot, the visible symptoms, is caused by plant cell wall degrading enzymes, mainly pectate lyases (Pels) that cleave the pectin polymer. However, an efficient colonization of the host requires many additional elements including early factors (eg, flagella, lipopolysaccharide, and exopolysaccharide) that allow adhesion of the bacteria and intermediate factors involved in adaptation to new growth conditions encountered in the host (eg, oxidative stress, iron starvation, and toxic compounds). To facilitate this adaptation, Dickeya have developed complex regulatory networks ensuring appropriate expression of virulence genes. This review presents recent advances in our understanding of the signals and genetic circuits impacting the expression of virulence determinants. Special attention is paid to integrated control of virulence functions by variations in the superhelical density of chromosomal DNA, and the global and specific regulators, making the regulation of Dickeya virulence an especially attractive model for those interested in relationships between the chromosomal dynamics and gene regulatory networks.
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Affiliation(s)
- S Reverchon
- Department of Biology, University of Lyon, INSA-Lyon, Villeurbanne, Lyon, France.
| | - G Muskhelisvili
- Department of Biology, University of Lyon, INSA-Lyon, Villeurbanne, Lyon, France
| | - W Nasser
- Department of Biology, University of Lyon, INSA-Lyon, Villeurbanne, Lyon, France
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Joshi JR, Burdman S, Lipsky A, Yariv S, Yedidia I. Plant phenolic acids affect the virulence of Pectobacterium aroidearum and P. carotovorum ssp. brasiliense via quorum sensing regulation. MOLECULAR PLANT PATHOLOGY 2016; 17:487-500. [PMID: 26177258 PMCID: PMC6638513 DOI: 10.1111/mpp.12295] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Several studies have reported effects of the plant phenolic acids cinnamic acid (CA) and salicylic acid (SA) on the virulence of soft rot enterobacteria. However, the mechanisms involved in these processes are not yet fully understood. Here, we investigated whether CA and SA interfere with the quorum sensing (QS) system of two Pectobacterium species, P. aroidearum and P. carotovorum ssp. brasiliense, which are known to produce N-acyl-homoserine lactone (AHL) QS signals. Our results clearly indicate that both phenolic compounds affect the QS machinery of the two species, consequently altering the expression of bacterial virulence factors. Although, in control treatments, the expression of QS-related genes increased over time, the exposure of bacteria to non-lethal concentrations of CA or SA inhibited the expression of QS genes, including expI, expR, PC1_1442 (luxR transcriptional regulator) and luxS (a component of the AI-2 system). Other virulence genes known to be regulated by the QS system, such as pecS, pel, peh and yheO, were also down-regulated relative to the control. In agreement with the low levels of expression of expI and expR, CA and SA also reduced the level of the AHL signal. The effects of CA and SA on AHL signalling were confirmed in compensation assays, in which exogenous application of N-(β-ketocaproyl)-l-homoserine lactone (eAHL) led to the recovery of the reduction in virulence caused by the two phenolic acids. Collectively, the results of gene expression studies, bioluminescence assays, virulence assays and compensation assays with eAHL clearly support a mechanism by which CA and SA interfere with Pectobacterium virulence via the QS machinery.
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Affiliation(s)
- Janak Raj Joshi
- Department of Plant Pathology and Microbiology and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, 76100, Rehovot, Israel
- Department of Plant Sciences, Agricultural Research Organization, The Volcani Center, 50250, Bet Dagan, Israel
| | - Saul Burdman
- Department of Plant Pathology and Microbiology and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, 76100, Rehovot, Israel
| | - Alexander Lipsky
- Department of Plant Sciences, Agricultural Research Organization, The Volcani Center, 50250, Bet Dagan, Israel
| | - Shaked Yariv
- Department of Plant Sciences, Agricultural Research Organization, The Volcani Center, 50250, Bet Dagan, Israel
| | - Iris Yedidia
- Department of Plant Sciences, Agricultural Research Organization, The Volcani Center, 50250, Bet Dagan, Israel
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Jiang X, Zghidi-Abouzid O, Oger-Desfeux C, Hommais F, Greliche N, Muskhelishvili G, Nasser W, Reverchon S. Global transcriptional response of Dickeya dadantii to environmental stimuli relevant to the plant infection. Environ Microbiol 2016; 18:3651-3672. [PMID: 26940633 DOI: 10.1111/1462-2920.13267] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 02/14/2016] [Indexed: 11/28/2022]
Abstract
Dickeya species are soft rot disease-causing bacterial plant pathogens and an emerging agricultural threat in Europe. Environmental modulation of gene expression is critical for Dickeya dadantii pathogenesis. While the bacterium uses various environmental cues to distinguish between its habitats, an intricate transcriptional control system coordinating the expression of virulence genes ensures efficient infection. Understanding of this behaviour requires a detailed knowledge of expression patterns under a wide range of environmental conditions, which is currently lacking. To obtain a comprehensive picture of this adaptive response, we devised a strategy to examine the D. dadantii transcriptome in a series of 32 infection-relevant conditions encountered in the hosts. We propose a temporal map of the bacterial response to various stress conditions and show that D. dadantii elicits complex genetic behaviour combining common stress-response genes with distinct sets of genes specifically induced under each particular stress. Comparison of our dataset with an in planta expression profile reveals the combined impact of stress factors and enables us to predict the major stress confronting D. dadantii at a particular stage of infection. We provide a comprehensive catalog of D. dadantii genomic responses to environmentally relevant stimuli, thus facilitating future studies of this important plant pathogen.
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Affiliation(s)
- Xuejiao Jiang
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - Ouafa Zghidi-Abouzid
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - Christine Oger-Desfeux
- Univ Lyon, Université Lyon 1, Pôle Rhône-Alpes de Bioinformatique, Département Biologie, F-69622, Villeurbanne, France
| | - Florence Hommais
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - Nicolas Greliche
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - Georgi Muskhelishvili
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - William Nasser
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
| | - Sylvie Reverchon
- Univ Lyon, Université Lyon 1, INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, Département Biologie, F-69622, Villeurbanne, France
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Roy A, Ranjan A. HosA, a MarR Family Transcriptional Regulator, Represses Nonoxidative Hydroxyarylic Acid Decarboxylase Operon and Is Modulated by 4-Hydroxybenzoic Acid. Biochemistry 2016; 55:1120-34. [PMID: 26818787 DOI: 10.1021/acs.biochem.5b01163] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Members of the Multiple antibiotic resistance Regulator (MarR) family of DNA binding proteins regulate transcription of a wide array of genes required for virulence and pathogenicity of bacteria. The present study reports the molecular characterization of HosA (Homologue of SlyA), a MarR protein, with respect to its target gene, DNA recognition motif, and nature of its ligand. Through a comparative genomics approach, we demonstrate that hosA is in synteny with nonoxidative hydroxyarylic acid decarboxylase (HAD) operon and is present exclusively within the mutS-rpoS polymorphic region in nine different genera of Enterobacteriaceae family. Using molecular biology and biochemical approach, we demonstrate that HosA binds to a palindromic sequence downstream to the transcription start site of divergently transcribed nonoxidative HAD operon and represses its expression. Furthermore, in silico analysis showed that the recognition motif for HosA is highly conserved in the upstream region of divergently transcribed operon in different genera of Enterobacteriaceae family. A systematic chemical search for the physiological ligand revealed that 4-hydroxybenzoic acid (4-HBA) interacts with HosA and derepresses HosA mediated repression of the nonoxidative HAD operon. Based on our study, we propose a model for molecular mechanism underlying the regulation of nonoxidative HAD operon by HosA in Enterobacteriaceae family.
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Affiliation(s)
- Ajit Roy
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500001, India.,Graduate studies, Manipal University , Manipal 576104, India
| | - Akash Ranjan
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500001, India
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Thekkiniath J, Ravirala R, San Francisco M. Multidrug Efflux Pumps in the Genus Erwinia: Physiology and Regulation of Efflux Pump Gene Expression. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 142:131-49. [DOI: 10.1016/bs.pmbts.2016.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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35
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Pagliai FA, Gonzalez CF, Lorca GL. Identification of a Ligand Binding Pocket in LdtR from Liberibacter asiaticus. Front Microbiol 2015; 6:1314. [PMID: 26635775 PMCID: PMC4658428 DOI: 10.3389/fmicb.2015.01314] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/09/2015] [Indexed: 11/13/2022] Open
Abstract
LdtR is a transcriptional activator involved in the regulation of a putative L,D transpeptidase in Liberibacter asiaticus, an unculturable pathogen and one of the causative agents of Huanglongbing disease. Using small molecule screens we identified benzbromarone as an inhibitor of LdtR activity, which was confirmed using in vivo and in vitro assays. Based on these previous results, the objective of this work was to identify the LdtR ligand binding pocket and characterize its interactions with benzbromarone. A structural model of LdtR was constructed and the molecular interactions with the ligand were predicted using the SwissDock interface. Using site-directed mutagenesis, these residues were changed to alanine. Electrophoretic mobility shift assays, thermal denaturation, isothermal titration calorimetry experiments, and in vivo assays were used to identify residues T43, L61, and F64 in the Benz1 pocket of LdtR as the amino acids most likely involved in the binding to benzbromarone. These results provide new information on the binding mechanism of LdtR to a modulatory molecule and provide a blue print for the design of therapeutics for other members of the MarR family of transcriptional regulators involved in pathogenicity.
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Affiliation(s)
- Fernando A Pagliai
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute and Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL, USA
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36
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Yuan X, Khokhani D, Wu X, Yang F, Biener G, Koestler BJ, Raicu V, He C, Waters CM, Sundin GW, Tian F, Yang CH. Cross-talk between a regulatory small RNA, cyclic-di-GMP signalling and flagellar regulator FlhDC for virulence and bacterial behaviours. Environ Microbiol 2015; 17:4745-63. [PMID: 26462993 DOI: 10.1111/1462-2920.13029] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/14/2015] [Accepted: 08/15/2015] [Indexed: 12/01/2022]
Abstract
Dickeya dadantii is a globally dispersed phytopathogen which causes diseases on a wide range of host plants. This pathogen utilizes the type III secretion system (T3SS) to suppress host defense responses, and secretes pectate lyase (Pel) to degrade the plant cell wall. Although the regulatory small RNA (sRNA) RsmB, cyclic diguanylate monophosphate (c-di-GMP) and flagellar regulator have been reported to affect the regulation of these two virulence factors or multiple cell behaviours such as motility and biofilm formation, the linkage between these regulatory components that coordinate the cell behaviours remain unclear. Here, we revealed a sophisticated regulatory network that connects the sRNA, c-di-GMP signalling and flagellar master regulator FlhDC. We propose multi-tiered regulatory mechanisms that link the FlhDC to the T3SS through three distinct pathways including the FlhDC-FliA-YcgR3937 pathway; the FlhDC-EcpC-RpoN-HrpL pathway; and the FlhDC-rsmB-RsmA-HrpL pathway. Among these, EcpC is the most dominant factor for FlhDC to positively regulate T3SS expression.
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Affiliation(s)
- Xiaochen Yuan
- Department of Biological Sciences, University of Wisconsin, Milwaukee, WI, 53211, USA
| | - Devanshi Khokhani
- Department of Biological Sciences, University of Wisconsin, Milwaukee, WI, 53211, USA
| | - Xiaogang Wu
- Department of Biological Sciences, University of Wisconsin, Milwaukee, WI, 53211, USA
| | - Fenghuan Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Gabriel Biener
- Department of Physics, University of Wisconsin, Milwaukee, WI, 53211, USA
| | - Benjamin J Koestler
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - Valerica Raicu
- Department of Biological Sciences, University of Wisconsin, Milwaukee, WI, 53211, USA.,Department of Physics, University of Wisconsin, Milwaukee, WI, 53211, USA
| | - Chenyang He
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Christopher M Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - George W Sundin
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA
| | - Fang Tian
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Ching-Hong Yang
- Department of Biological Sciences, University of Wisconsin, Milwaukee, WI, 53211, USA
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37
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Wang ZC, Liu CJ, Huang YJ, Wang YS, Peng HL. PecS regulates the urate-responsive expression of type 1 fimbriae in Klebsiella pneumoniae CG43. MICROBIOLOGY-SGM 2015; 161:2395-409. [PMID: 26385366 DOI: 10.1099/mic.0.000185] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the Klebsiella pneumoniae CG43 genome, the divergently transcribed genes coding for PecS, the MarR-type transcription factor, and PecM, the drug metabolite transporter, are located between the type 1 and type 3 fimbrial gene clusters. The intergenic sequence pecO between pecS and pecM contains three putative PecS binding sites and a CpxR box. Electrophoretic mobility shift assay revealed that the recombinant PecS and CpxR could specifically bind to the pecO sequence, and the specific interaction of PecS and pecO could be attenuated by urate. The expression of pecS and pecM was negatively regulated by CpxAR and PecS, and was inducible by exogenous urate in the absence of cpxAR. Compared with CG43S3ΔcpxAR, the derived mutants CG43S3ΔcpxARΔpecS and CG43S3ΔcpxARΔpecSΔpecM exerted similar levels of sensitivity to H2O2 or paraquat, but higher levels of mannose-sensitive yeast agglutination activity and FimA production. The promoter activity and transcript levels of fimA in CG43S3ΔcpxAR were also increased by deleting pecS. However, no binding activity between PecS and the fimA promoter could be observed. Nevertheless, PecS deletion could reduce the expression of the global regulator HNS and release the negative effect of HNS on FimA expression. In CG43S3ΔcpxAR, the expression of FimA as well as PecS was inducible by urate, whilst urate-induced FimA expression was inhibited by the deletion of pecS. Taken together, we propose that K. pneumoniae PecS indirectly and negatively regulates the expression of type 1 fimbriae, and the regulation is urate-inducible in the absence of CpxAR.
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Affiliation(s)
- Zhe-Chong Wang
- 1 Department of Biological Science and Technology, School of Biological Science and Technology, National Chiao Tung University, Hsin Chu, ROC
| | - Chia-Jui Liu
- 1 Department of Biological Science and Technology, School of Biological Science and Technology, National Chiao Tung University, Hsin Chu, ROC
| | - Ying-Jung Huang
- 2 Division of Hematology-Oncology, Chang Gung Memorial Hospital, Tao Yuan, ROC
| | - Yu-Seng Wang
- 1 Department of Biological Science and Technology, School of Biological Science and Technology, National Chiao Tung University, Hsin Chu, ROC
| | - Hwei-Ling Peng
- 1 Department of Biological Science and Technology, School of Biological Science and Technology, National Chiao Tung University, Hsin Chu, ROC
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38
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Dequivre M, Diel B, Villard C, Sismeiro O, Durot M, Coppée JY, Nesme X, Vial L, Hommais F. Small RNA Deep-Sequencing Analyses Reveal a New Regulator of Virulence in Agrobacterium fabrum C58. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:580-589. [PMID: 26024442 DOI: 10.1094/mpmi-12-14-0380-fi] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) that are known to act as posttranscriptional regulators in plant pathogenic bacteria. sRNA-seq analyses of Agrobacterium fabrum C58 allowed us to identify 1,108 small transcripts expressed in several growth conditions that could be sRNAs. A quarter of them were confirmed by bioinformatics or by biological experiments. Antisense RNAs represent 24% of the candidates and they are over-represented on the pTi (with 62% of pTi sRNAs), suggesting differences in the regulatory mechanisms between the essential and accessory replicons. Moreover, a large number of these pTi antisense RNAs are transcribed opposite to those genes involved in virulence. Others are 5'- and 3'-untranslated region RNAs and trans-encoded RNAs. We have validated, by rapid amplification of cDNA ends polymerase chain reaction, the transcription of 14 trans-encoded RNAs, among which RNA1111 is expressed from the pTiC58. Its deletion decreased the aggressiveness of A. fabrum C58 on tomatoes, tobaccos, and kalanchoe, suggesting that this sRNA activates virulence. The identification of its putative target mRNAs (6b gene, virC2, virD3, and traA) suggests that this sRNA may coordinate two of the major pTi functions, the infection of plants and its dissemination among bacteria.
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Affiliation(s)
- M Dequivre
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 3CNRS, UMR 5240 Microbiologie Adaptation et Pathogénie, F-69622 Villeurbanne, France
| | - B Diel
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 3CNRS, UMR 5240 Microbiologie Adaptation et Pathogénie, F-69622 Villeurbanne, France
- 4CNRS, UMR 5557 Ecologie Microbienne, F-69622 Villeurbanne, France
- 5INRA, USC 1364 Ecologie Microbienne, F-69622 Villeurbanne, France
| | - C Villard
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 3CNRS, UMR 5240 Microbiologie Adaptation et Pathogénie, F-69622 Villeurbanne, France
| | - O Sismeiro
- 6Plate-forme Transcriptome et Epigénome, Département Génomes et Génétique, Institut Pasteur, 25 rue du Dr. Roux, F75015 Paris, France
| | - M Durot
- 7CEA/DSV/FAR/IG/Genoscope and CNRS UMR8030 Laboratoire d'Analyses Bioinformatiques en Métabolisme et Génomique, 2 rue Gaston Crémieux 91057 Evry cedex, France
- 8Total New Energies USA, 5858 Horton Street, Emeryville, CA 94608, U.S.A
| | - J Y Coppée
- 6Plate-forme Transcriptome et Epigénome, Département Génomes et Génétique, Institut Pasteur, 25 rue du Dr. Roux, F75015 Paris, France
| | - X Nesme
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 4CNRS, UMR 5557 Ecologie Microbienne, F-69622 Villeurbanne, France
- 5INRA, USC 1364 Ecologie Microbienne, F-69622 Villeurbanne, France
| | - L Vial
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 4CNRS, UMR 5557 Ecologie Microbienne, F-69622 Villeurbanne, France
- 5INRA, USC 1364 Ecologie Microbienne, F-69622 Villeurbanne, France
| | - F Hommais
- 1Université de Lyon, F-69622, Lyon, France
- 2Université Lyon 1, F-69622 Villeurbanne, France
- 3CNRS, UMR 5240 Microbiologie Adaptation et Pathogénie, F-69622 Villeurbanne, France
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39
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Shu HY, Lin LC, Lin TK, Chen HP, Yang HH, Peng KC, Lin GH. Transcriptional regulation of the iac locus from Acinetobacter baumannii by the phytohormone indole-3-acetic acid. Antonie van Leeuwenhoek 2015; 107:1237-47. [PMID: 25726082 DOI: 10.1007/s10482-015-0417-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 02/24/2015] [Indexed: 11/25/2022]
Abstract
The iac locus is involved in indole-3-acetic acid (IAA) catabolism in Acinetobacter baumannii. Nine structural genes of iac are transcribed in the same direction, whereas iacR, which encodes a MarR-type transcriptional regulator, is transcribed in the opposite direction. The IacA protein, which is encoded by the second structural gene of the iac locus, is expressed in an IAA-dependent manner. Here, we characterized gene expression from this locus in wild type A. baumannii and in an iacR mutant; this revealed that the iacH promoter is negatively regulated by IacR. The transcriptional site of iacH was determined by using 5' rapid amplification of cDNA ends; one IacR-binding site was identified between positions -35 and +28 of the iacH promoter. Sequence analysis and an electrophoretic mobility shift assay indicated that recombinant IacR binds specifically to a sequence with dyad symmetry in the iacR-iacH overlapping promoters in the absence of IAA. In addition, a two-plasmid expression system in Escherichia coli showed that IAA probably serves as a ligand that binds to IacR and releases it from the iacH promoter, thereby allowing RNA polymerase to transcribe iac. Thus, iac is expressed in order to promote IAA degradation, whereas free IacR is required for iac repression. We conclude that IacR serves as a key regulator of IAA degradation in A. baumannii in the rhizosphere. These results provide new insights into the possible role of A. baumannii in the environment.
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Affiliation(s)
- Hung-Yu Shu
- Department of Bioscience Technology, Chang Jung Christian University, Tainan, 711, Taiwan
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40
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Potrykus M, Golanowska M, Hugouvieux-Cotte-Pattat N, Lojkowska E. Regulators Involved in Dickeya solani Virulence, Genetic Conservation and Functional Variability. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 2015:57-68. [PMID: 27839073 DOI: 10.1094/mpmi-99-99-0003-r.testissue] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bacteria from the genus Dickeya (formerly Erwinia chrysanthemi) are plant pathogens causing severe diseases in many economically important crops. A majority of the strains responsible for potato disease in Europe belong to a newly identified Dickeya solani species. Although some ecological and epidemiological studies have been carried out, little is known about the regulation of D. solani virulence. The characterization of four D. solani strains indicates significant differences in their virulence on potato although they are genetically similar based on genomic fingerprinting profiles. A phenotypic examination included an analysis of virulence on potato, growth rate in culture, motility, Fe3+ chelation, and pectate lyase, cellulase, protease, biosurfactant and blue pigment production. Mutants of four D. solani strains were constructed by inactivating the genes coding either for one of the main negative regulators of D. dadantii virulence (kdgR, pecS and pecT) or for the synthesis and perception of signaling molecules (expI and expR). Analysis of these mutants indicated that PecS, PecT and KdgR play a similar role in both species, repressing to different degrees the synthesis of virulence factors. The thermoregulator PecT seems to be a major regulator of D. solani virulence. This work also reveals the role of quorum sensing mediated by ExpI and ExpR in D. solani virulence on potato.
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Affiliation(s)
- Marta Potrykus
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
| | - Małgorzata Golanowska
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
| | | | - Ewa Lojkowska
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
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41
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Potrykus M, Golanowska M, Hugouvieux-Cotte-Pattat N, Lojkowska E. Regulators Involved in Dickeya solani Virulence, Genetic Conservation and Functional Variability. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 2015:5-16. [PMID: 27839070 DOI: 10.1094/mpmi-99-99-0004-le.testissue] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bacteria from the genus Dickeya (formerly Erwinia chrysanthemi) are plant pathogens causing severe diseases in many economically important crops. A majority of the strains responsible for potato disease in Europe belong to a newly identified Dickeya solani species. Although some ecological and epidemiological studies have been carried out, little is known about the regulation of D. solani virulence. The characterization of four D. solani strains indicates significant differences in their virulence on potato although they are genetically similar based on genomic fingerprinting profiles. A phenotypic examination included an analysis of virulence on potato, growth rate in culture, motility, Fe3+ chelation, and pectate lyase, cellulase, protease, biosurfactant and blue pigment production. Mutants of four D. solani strains were constructed by inactivating the genes coding either for one of the main negative regulators of D. dadantii virulence (kdgR, pecS and pecT) or for the synthesis and perception of signaling molecules (expI and expR). Analysis of these mutants indicated that PecS, PecT and KdgR play a similar role in both species, repressing to different degrees the synthesis of virulence factors. The thermoregulator PecT seems to be a major regulator of D. solani virulence. This work also reveals the role of quorum sensing mediated by ExpI and ExpR in D. solani virulence on potato.
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Affiliation(s)
- Marta Potrykus
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
| | - Małgorzata Golanowska
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
| | | | - Ewa Lojkowska
- 1 Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 Gdansk, Poland
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42
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Madec E, Bontemps-Gallo S, Lacroix JM. Increased phosphorylation of the RcsB regulator of the RcsCDB phosphorelay in strains of Dickeya dadantii devoid of osmoregulated periplasmic glucans revealed by Phos-tag gel analysis. MICROBIOLOGY-SGM 2014; 160:2763-2770. [PMID: 25320363 DOI: 10.1099/mic.0.081273-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Osmoregulated periplasmic glucans (OPGs) are general constituents of many proteobacteria. OPGs are important factors required for full virulence in many pathogens including Dickeya dadantii. D. dadantii causes the soft-rot disease in a wide range of plant species. The pleiotropic phenotype of opg-negative strains includes total loss of virulence and motility, and is linked to the constitutive activation of the RcsCDB phosphorelay, deduced from expression analysis of genes of the RcsCDB regulon. The constitutive activation of the RcsCDB phosphorelay in an opg-negative strain was demonstrated by direct analysis of the phosphorylation level of the RcsB regulator protein in vivo by using a Phos-tag retardation gel approach, and was correlated with the phenotype and the expression of motility genes. Data revealed a low level of RcsB phosphorylated form in the wild-type strain and a slight increase of phosphorylation in opgG mutant strains sufficient to induce the pleiotropic phenotype observed.
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Affiliation(s)
- Edwige Madec
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR 8576 Lille 1-CNRS, Université des Sciences et Technologies de Lille, Université Lille - Nord de France, 59655 Villeneuve d'Ascq, France
| | - Sébastien Bontemps-Gallo
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR 8576 Lille 1-CNRS, Université des Sciences et Technologies de Lille, Université Lille - Nord de France, 59655 Villeneuve d'Ascq, France
| | - Jean-Marie Lacroix
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR 8576 Lille 1-CNRS, Université des Sciences et Technologies de Lille, Université Lille - Nord de France, 59655 Villeneuve d'Ascq, France
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43
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Potrykus M, Golanowska M, Hugouvieux-Cotte-Pattat N, Lojkowska E. Regulators involved in Dickeya solani virulence, genetic conservation, and functional variability. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:700-11. [PMID: 24625032 DOI: 10.1094/mpmi-09-13-0270-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Bacteria from the genus Dickeya (formerly Erwinia chrysanthemi) are plant pathogens causing severe diseases in many economically important crops. A majority of the strains responsible for potato disease in Europe belong to a newly identified Dickeya solani species. Although some ecological and epidemiological studies have been carried out, little is known about the regulation of D. solani virulence. The characterization of four D. solani strains indicates significant differences in their virulence on potato, although they are genetically similar based on genomic fingerprinting profiles. A phenotypic examination included an analysis of virulence on potato; growth rate in culture; motility; Fe3+ chelation; and pectate lyase, cellulase, protease, biosurfactant, and blue pigment production. Mutants of four D. solani strains were constructed by inactivating the genes coding either for one of the main negative regulators of D. dadantii virulence (kdgR, pecS, and pecT) or for the synthesis and perception of signaling molecules (expI and expR). Analysis of these mutants indicated that PecS, PecT, and KdgR play a similar role in both species, repressing, to different degrees, the synthesis of virulence factors. The thermoregulator PecT seems to be a major regulator of D. solani virulence. This work also reveals the role of quorum sensing mediated by ExpI and ExpR in D. solani virulence on potato.
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44
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Gupta A, Grove A. Ligand-binding pocket bridges DNA-binding and dimerization domains of the urate-responsive MarR homologue MftR from Burkholderia thailandensis. Biochemistry 2014; 53:4368-80. [PMID: 24955985 PMCID: PMC4100783 DOI: 10.1021/bi500219t] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
![]()
Members of the multiple antibiotic
resistance regulator (MarR)
family often regulate gene activity by responding to a specific ligand.
In the absence of ligand, most MarR proteins function as repressors,
while ligand binding causes attenuated DNA binding and therefore increased
gene expression. Previously, we have shown that urate is a ligand
for MftR (major facilitator transport regulator), which is encoded
by the soil bacterium Burkholderia thailandensis.
We show here that both mftR and the divergently oriented
gene mftP encoding a major facilitator transport
protein are upregulated in the presence of urate. MftR binds two cognate
sites in the mftR-mftP intergenic region with equivalent
affinity and sensitivity to urate. Mutagenesis of four conserved residues
previously reported to be involved in urate binding to Deinococcus
radiodurans HucR and Rhizobium radiobacter PecS significantly reduced protein stability and DNA binding affinity
but not ligand binding. These data suggest that residues equivalent
to those implicated in ligand binding to HucR and PecS serve structural
roles and that MftR relies on distinct residues for ligand binding.
MftR exhibits a two-step melting transition suggesting independent
unfolding of the dimerization and DNA-binding regions; urate binding
or mutations in the predicted ligand-binding sites result in one-step
unfolding transitions. We suggest that MftR binds the ligand in a
cleft between the DNA-binding lobes and the dimer interface but that
the mechanism of ligand-mediated attenuation of DNA binding differs
from that proposed for other urate-responsive MarR homologues. Since
DNA binding by MftR is attenuated at 37 °C, our data also suggest
that MftR responds to both ligand and a thermal upshift by attenuated
DNA binding and upregulation of the genes under its control.
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Affiliation(s)
- Ashish Gupta
- Department of Biological Sciences, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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Ma B, Charkowski AO, Glasner JD, Perna NT. Identification of host-microbe interaction factors in the genomes of soft rot-associated pathogens Dickeya dadantii 3937 and Pectobacterium carotovorum WPP14 with supervised machine learning. BMC Genomics 2014; 15:508. [PMID: 24952641 PMCID: PMC4079955 DOI: 10.1186/1471-2164-15-508] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 06/09/2014] [Indexed: 12/14/2022] Open
Abstract
Background A wealth of genome sequences has provided thousands of genes of unknown function, but identification of functions for the large numbers of hypothetical genes in phytopathogens remains a challenge that impacts all research on plant-microbe interactions. Decades of research on the molecular basis of pathogenesis focused on a limited number of factors associated with long-known host-microbe interaction systems, providing limited direction into this challenge. Computational approaches to identify virulence genes often rely on two strategies: searching for sequence similarity to known host-microbe interaction factors from other organisms, and identifying islands of genes that discriminate between pathogens of one type and closely related non-pathogens or pathogens of a different type. The former is limited to known genes, excluding vast collections of genes of unknown function found in every genome. The latter lacks specificity, since many genes in genomic islands have little to do with host-interaction. Result In this study, we developed a supervised machine learning approach that was designed to recognize patterns from large and disparate data types, in order to identify candidate host-microbe interaction factors. The soft rot Enterobacteriaceae strains Dickeya dadantii 3937 and Pectobacterium carotovorum WPP14 were used for development of this tool, because these pathogens are important on multiple high value crops in agriculture worldwide and more genomic and functional data is available for the Enterobacteriaceae than any other microbial family. Our approach achieved greater than 90% precision and a recall rate over 80% in 10-fold cross validation tests. Conclusion Application of the learning scheme to the complete genome of these two organisms generated a list of roughly 200 candidates, many of which were previously not implicated in plant-microbe interaction and many of which are of completely unknown function. These lists provide new targets for experimental validation and further characterization, and our approach presents a promising pattern-learning scheme that can be generalized to create a resource to study host-microbe interactions in other bacterial phytopathogens. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-508) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Bing Ma
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI 53706, USA.
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46
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Gao D, Cheng J, Zheng E, Li Y, Shao Z, Xu Z, Lu C. Eha, a transcriptional regulator of hemolytic activity ofEdwardsiella tarda. FEMS Microbiol Lett 2014; 353:132-40. [DOI: 10.1111/1574-6968.12420] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/02/2014] [Accepted: 03/07/2014] [Indexed: 11/29/2022] Open
Affiliation(s)
- Daqing Gao
- Department of Pathogenic Microbiology and Immunology; Southeast University School of Medicine; Nanjing China
| | - Jing Cheng
- JiangSu University School of Medicine; Zhenjiang China
| | - Enjin Zheng
- Department of Pathogenic Microbiology and Immunology; Southeast University School of Medicine; Nanjing China
| | - Yuhong Li
- Department of Pathogenic Microbiology and Immunology; Southeast University School of Medicine; Nanjing China
| | - Zeye Shao
- Department of Clinical Lab; Southeast University School of Medicine; Nanjing China
| | - Zeyan Xu
- JiangSu University School of Medicine; Zhenjiang China
| | - Chengping Lu
- NanJing Agricultural University, College of Veterinary Medicine; Nanjing China
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47
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Bontemps-Gallo S, Madec E, Lacroix JM. Inactivation of pecS restores the virulence of mutants devoid of osmoregulated periplasmic glucans in the phytopathogenic bacterium Dickeya dadantii. MICROBIOLOGY-SGM 2014; 160:766-777. [PMID: 24550070 DOI: 10.1099/mic.0.074484-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Dickeya dadantii is a phytopathogenic enterobacterium that causes soft rot disease in a wide range of plant species. Maceration, an apparent symptom of the disease, is the result of the synthesis and secretion of a set of plant cell wall-degrading enzymes (PCWDEs), but many additional factors are required for full virulence. Among these, osmoregulated periplasmic glucans (OPGs) and the PecS transcriptional regulator are essential virulence factors. Several cellular functions are controlled by both OPGs and PecS. Strains devoid of OPGs display a pleiotropic phenotype including total loss of virulence, loss of motility and severe reduction in the synthesis of PCWDEs. PecS is one of the major regulators of virulence in D. dadantii, acting mainly as a repressor of various cellular functions including virulence, motility and synthesis of PCWDEs. The present study shows that inactivation of the pecS gene restored virulence in a D. dadantii strain devoid of OPGs, indicating that PecS cannot be de-repressed in strains devoid of OPGs.
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Affiliation(s)
- Sébastien Bontemps-Gallo
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, Université des Sciences et Technologies de Lille, Université Lille Nord de France, F-59655 Villeneuve d'Ascq, France
| | - Edwige Madec
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, Université des Sciences et Technologies de Lille, Université Lille Nord de France, F-59655 Villeneuve d'Ascq, France
| | - Jean-Marie Lacroix
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, Université des Sciences et Technologies de Lille, Université Lille Nord de France, F-59655 Villeneuve d'Ascq, France
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Duprey A, Reverchon S, Nasser W. Bacterial virulence and Fis: adapting regulatory networks to the host environment. Trends Microbiol 2013; 22:92-9. [PMID: 24370464 DOI: 10.1016/j.tim.2013.11.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 11/18/2022]
Abstract
Pathogenic bacteria have to cope with adverse conditions, such as the host environment and host defense reactions. To adapt quickly to environmental changes, pathogens have developed complex regulatory networks that ensure adequate expression of their virulence genes. Recent evidence suggests that Fis, an abundant nucleoid-associated protein transiently produced during early exponential growth, plays a major role in these networks in several pathogenic bacteria. This review focuses on two enterobacteria, Salmonella enterica and Dickeya dadantii, that inhabit distinct ecological niches to illustrate how Fis uses different strategies to coordinate virulence gene expression, depending on the bacterial lifestyle.
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Affiliation(s)
- Alexandre Duprey
- Université Lyon 1, F-69622 Villeurbanne, France; INSA de Lyon, F-69621 Villeurbanne, France; CNRS UMR5240 Microbiologie, Adaptation et Pathogénie, Villeurbanne, France
| | - Sylvie Reverchon
- Université Lyon 1, F-69622 Villeurbanne, France; INSA de Lyon, F-69621 Villeurbanne, France; CNRS UMR5240 Microbiologie, Adaptation et Pathogénie, Villeurbanne, France
| | - William Nasser
- Université Lyon 1, F-69622 Villeurbanne, France; INSA de Lyon, F-69621 Villeurbanne, France; CNRS UMR5240 Microbiologie, Adaptation et Pathogénie, Villeurbanne, France.
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Reverchon S, Nasser W. Dickeya ecology, environment sensing and regulation of virulence programme. ENVIRONMENTAL MICROBIOLOGY REPORTS 2013; 5:622-36. [PMID: 24115612 DOI: 10.1111/1758-2229.12073] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/25/2013] [Accepted: 05/27/2013] [Indexed: 05/05/2023]
Abstract
The pectinolytic Dickeya spp. are soft-rot Gram-negative bacteria that cause severe disease in a wide range of plant species. In recent years, there has been an increase in the damage caused by Dickeya in potato crops in Europe. Soft-rot symptoms are due to the production and secretion of degradative enzymes that destroy the plant cell wall. However, an efficient colonization of the host plant requires many additional bacterial factors, including elements in the early stages allowing for the adhesion and penetration of the bacteria in the plant and different elements in the intermediate stages, involved in the adaptation to the new growth conditions encountered in the host. Dickeya pathogenicity is clearly a multifactorial process, and successful infection by these bacteria requires a temporal coordination of survival and virulence gene expression. This involves the ancestral nucleoid-associated proteins, Fis and H-NS, and modifications of DNA topology, as well as various specific regulatory systems, including a new quorum-sensing pathway and regulators that sense the bacterial metabolic status or environmental stresses. This review presents new information concerning the ecology of Dickeya and the strategies used by this bacterium to coordinate its survival and virulence programmes during infection.
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Streptomyces coelicolor encodes a urate-responsive transcriptional regulator with homology to PecS from plant pathogens. J Bacteriol 2013; 195:4954-65. [PMID: 23995633 DOI: 10.1128/jb.00854-13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Many transcriptional regulators control gene activity by responding to specific ligands. Members of the multiple-antibiotic resistance regulator (MarR) family of transcriptional regulators feature prominently in this regard, and they frequently function as repressors in the absence of their cognate ligands. Plant pathogens such as Dickeya dadantii encode a MarR homolog named PecS that controls expression of a gene encoding the efflux pump PecM in addition to other virulence genes. We report here that the soil bacterium Streptomyces coelicolor also encodes a PecS homolog (SCO2647) that regulates a pecM gene (SCO2646). S. coelicolor PecS, which exists as a homodimer, binds the intergenic region between pecS and pecM genes with high affinity. Several potential PecS binding sites were found in this intergenic region. The binding of PecS to its target DNA can be efficiently attenuated by the ligand urate, which also quenches the intrinsic fluorescence of PecS, indicating a direct interaction between urate and PecS. In vivo measurement of gene expression showed that activity of pecS and pecM genes is significantly elevated after exposure of S. coelicolor cultures to urate. These results indicate that S. coelicolor PecS responds to the ligand urate by attenuated DNA binding in vitro and upregulation of gene activity in vivo. Since production of urate is associated with generation of reactive oxygen species by xanthine dehydrogenase, we propose that PecS functions under conditions of oxidative stress.
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