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Du X, Li P, Fan C, Tian J, Lin Y, Xie J, Cheng J, Fu Y, Jiang D, Yuan M, Yu X, Tsuda K, Li B. Holliday junction resolvase RuvC targets biofilm eDNA and confers plant resistance to vascular pathogens. NATURE PLANTS 2024:10.1038/s41477-024-01817-6. [PMID: 39384943 DOI: 10.1038/s41477-024-01817-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 09/05/2024] [Indexed: 10/11/2024]
Abstract
A biofilm lifestyle is critical for bacterial pathogens to colonize and protect themselves from host immunity and antimicrobial chemicals in plants and animals. The formation and regulation mechanisms of phytobacterial biofilm are still obscure. Here we found that the protein Ralstonia solanacearum resistance to ultraviolet C (RuvC) is highly abundant in biofilm and positively regulates pathogenicity by controlling systemic movement in tomato xylem. RuvC protein accumulates at the later stage of biofilm development and specifically targets Holliday junction (HJ)-like structures to disrupt the biofilm extracellular DNA (eDNA) lattice, thus facilitating biofilm dispersal. Recombinant RuvC protein can resolve extracellular HJ to prevent bacterial biofilm formation. Heterologous expression of R. solanacearum or Xanthomonas oryzae pv. oryzae RuvC with plant secretion signal in tomato or rice confers resistance to bacterial wilt or bacterial blight disease, respectively. Plant chloroplast-localized HJ resolvase monokaryotic chloroplast 1 (MOC1), which shares structural similarity with bacterial RuvC, shows a strong inhibitory effect on bacterial biofilm formation. Relocalization of SlMOC1 to apoplast in tomato roots leads to increased resistance to bacterial wilt. Our novel finding reveals a critical pathogenesis mechanism of R. solanacearum and provides an efficient biotechnology strategy to improve plant resistance to bacterial vascular disease.
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Affiliation(s)
- Xinya Du
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Pengyue Li
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Changqiu Fan
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Jingjing Tian
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yang Lin
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Jiatao Xie
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Jiasen Cheng
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yanping Fu
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Daohong Jiang
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Meng Yuan
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Xiao Yu
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Kenichi Tsuda
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China
- Hubei Hongshan Laboratory, Wuhan, Hubei, China
| | - Bo Li
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China.
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
- Hubei Hongshan Laboratory, Wuhan, Hubei, China.
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de Pedro-Jové R, Corral J, Rocafort M, Puigvert M, Azam FL, Vandecaveye A, Macho AP, Balsalobre C, Coll NS, Orellano E, Valls M. Gene expression changes throughout the life cycle allow a bacterial plant pathogen to persist in diverse environmental habitats. PLoS Pathog 2023; 19:e1011888. [PMID: 38113281 PMCID: PMC10763947 DOI: 10.1371/journal.ppat.1011888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/03/2024] [Accepted: 12/07/2023] [Indexed: 12/21/2023] Open
Abstract
Bacterial pathogens exhibit a remarkable ability to persist and thrive in diverse ecological niches. Understanding the mechanisms enabling their transition between habitats is crucial to control dissemination and potential disease outbreaks. Here, we use Ralstonia solanacearum, the causing agent of the bacterial wilt disease, as a model to investigate pathogen adaptation to water and soil, two environments that act as bacterial reservoirs, and compare this information with gene expression in planta. Gene expression in water resembled that observed during late xylem colonization, with an intriguing induction of the type 3 secretion system (T3SS). Alkaline pH and nutrient scarcity-conditions also encountered during late infection stages-were identified as the triggers for this T3SS induction. In the soil environment, R. solanacearum upregulated stress-responses and genes for the use of alternate carbon sources, such as phenylacetate catabolism and the glyoxylate cycle, and downregulated virulence-associated genes. We proved through gain- and loss-of-function experiments that genes associated with the oxidative stress response, such as the regulator OxyR and the catalase KatG, are key for bacterial survival in soil, as their deletion cause a decrease in culturability associated with a premature induction of the viable but non culturable state (VBNC). This work identifies essential factors necessary for R. solanacearum to complete its life cycle and is the first comprehensive gene expression analysis in all environments occupied by a bacterial plant pathogen, providing valuable insights into its biology and adaptation to unexplored habitats.
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Affiliation(s)
- Roger de Pedro-Jové
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Jordi Corral
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Mercedes Rocafort
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Marina Puigvert
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Fàtima Latif Azam
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Agustina Vandecaveye
- Área Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-UNR-CONICET), Rosario, Santa Fe, Argentina
| | - Alberto P. Macho
- Shanghai Centre for Plant Stress Biology, CAS Centre for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Carlos Balsalobre
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
| | - Núria S. Coll
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
| | - Elena Orellano
- Área Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-UNR-CONICET), Rosario, Santa Fe, Argentina
| | - Marc Valls
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Catalonia, Spain
- Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Catalonia, Spain
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Cellier G, Nordey T, Cortada L, Gauche M, Rasoamanana H, Yahiaoui N, Rébert E, Prior P, Chéron JJ, Poussier S, Pruvost O. Molecular Epidemiology of Ralstonia pseudosolanacearum Phylotype I Strains in the Southwest Indian Ocean Region and Their Relatedness to African Strains. PHYTOPATHOLOGY 2023; 113:423-435. [PMID: 36399027 DOI: 10.1094/phyto-09-22-0355-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The increasing requirement for developing tools enabling fine strain traceability responsible for epidemics is tightly linked with the need to understand factors shaping pathogen populations and their environmental interactions. Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is one of the most important plant diseases in tropical and subtropical regions. Sadly, little, outdated, or no information on its epidemiology is reported in the literature, although alarming outbreaks are regularly reported as disasters. A large set of phylotype I isolates (n = 2,608) was retrieved from diseased plants in fields across the Southwest Indian Ocean (SWIO) and Africa. This collection enabled further assessment of the epidemiological discriminating power of the previously published RS1-MLVA14 scheme. Thirteen markers were validated and characterized as not equally informative. Most had little infra-sequevar polymorphism, and their performance depended on the sequevar. Strong correlation was found with a previous multilocus sequence typing scheme. However, 2 to 3% of sequevars were not correctly assigned through endoglucanase gene sequence. Discriminant analysis of principal components (DAPC) revealed four groups with strong phylogenetic relatedness to sequevars 31, 33, and 18. Phylotype I-31 isolates were highly prevalent in the SWIO and Africa, but their dissemination pathways remain unclear. Tanzania and Mauritius showed the greatest diversity of RSSC strains, as the four DAPC groups were retrieved. Mauritius was the sole territory harboring a vast phylogenetic diversity and all DAPC groups. More research is still needed to understand the high prevalence of phylotype I-31 at such a large geographic scale.
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Affiliation(s)
- Gilles Cellier
- Anses, Plant Health Laboratory, Saint Pierre, Reunion Island
| | | | - Laura Cortada
- East Africa Hub, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
- Nematology Section, Department of Biology, Ghent University, Ghent, Belgium
| | - Mirana Gauche
- University of Reunion Island, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Hasina Rasoamanana
- University of Reunion Island, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Noura Yahiaoui
- Anses, Plant Health Laboratory, Saint Pierre, Reunion Island
- University of Reunion Island, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Emeline Rébert
- University of Reunion Island, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Philippe Prior
- INRAE, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint-Pierre, Reunion Island
| | - Jean Jacques Chéron
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Stéphane Poussier
- University of Reunion Island, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
| | - Olivier Pruvost
- CIRAD, UMR Peuplements végétaux et bioagresseurs en milieu tropical, Saint Pierre, Reunion Island
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Plant-Pathogenic Ralstonia Phylotypes Evolved Divergent Respiratory Strategies and Behaviors To Thrive in Xylem. mBio 2023; 14:e0318822. [PMID: 36744950 PMCID: PMC9973335 DOI: 10.1128/mbio.03188-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Bacterial pathogens in the Ralstonia solanacearum species complex (RSSC) infect the water-transporting xylem vessels of plants, causing bacterial wilt disease. Strains in RSSC phylotypes I and III can reduce nitrate to dinitrogen via complete denitrification. The four-step denitrification pathway enables bacteria to use inorganic nitrogen species as terminal electron acceptors, supporting their growth in oxygen-limited environments such as biofilms or plant xylem. Reduction of nitrate, nitrite, and nitric oxide all contribute to the virulence of a model phylotype I strain. However, little is known about the physiological role of the last denitrification step, the reduction of nitrous oxide to dinitrogen by NosZ. We found that phylotypes I and III need NosZ for full virulence. However, strains in phylotypes II and IV are highly virulent despite lacking NosZ. The ability to respire by reducing nitrate to nitrous oxide does not greatly enhance the growth of phylotype II and IV strains. These partial denitrifying strains reach high cell densities during plant infection and cause typical wilt disease. However, unlike phylotype I and III strains, partial denitrifiers cannot grow well under anaerobic conditions or form thick biofilms in culture or in tomato xylem vessels. Furthermore, aerotaxis assays show that strains from different phylotypes have different oxygen and nitrate preferences. Together, these results indicate that the RSSC contains two subgroups that occupy the same habitat but have evolved divergent energy metabolism strategies to exploit distinct metabolic niches in the xylem. IMPORTANCE Plant-pathogenic Ralstonia spp. are a heterogeneous globally distributed group of bacteria that colonize plant xylem vessels. Ralstonia cells multiply rapidly in plants and obstruct water transport, causing fatal wilting and serious economic losses of many key food security crops. The virulence of these pathogens depends on their ability to grow to high cell densities in the low-oxygen xylem environment. Plant-pathogenic Ralstonia can use denitrifying respiration to generate ATP. The last denitrification step, nitrous oxide reduction by NosZ, contributes to energy production and virulence for only one of the three phytopathogenic Ralstonia species. These complete denitrifiers form thicker biofilms in culture and in tomato xylem, suggesting they are better adapted to hypoxic niches. Strains with partial denitrification physiology form less biofilm and are more often planktonic. They are nonetheless highly virulent. Thus, these closely related bacteria have adapted their core metabolic functions to exploit distinct microniches in the same habitat.
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Yan J, Lin N, Wang X, Chen X, Wang H, Lin Q, Zhou X, Zhang L, Liao L. Markerless gene deletion in Ralstonia solanacearum based on its natural transformation competence. Front Microbiol 2022; 13:977580. [PMID: 36177460 PMCID: PMC9512648 DOI: 10.3389/fmicb.2022.977580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/26/2022] [Indexed: 11/25/2022] Open
Abstract
Ralstonia solanacearum species complex (RSSC) is a group of Gram-negative bacterial pathogen capable of infecting numerous plants and crops, causing severe vascular wilt diseases. Functional analysis of the genes associated with bacterial virulence is critical for elucidating the molecular mechanisms that govern the bacterial pathogenicity. To this end, an efficient gene deletion method would be of great help. In this study, we set to develop an efficient and simple markerless gene deletion method by exploiting its natural transformation competence and the FLP/FRT recombination system. We found that natural transformation using PCR products provided much higher transformation frequency than the plasmid-based triparental mating and electroporation. We thus generated the gene deletion fusion PCR fragments by incorporating the upstream and downstream DNA fragments of the target gene and an antibiotic resistance gene flanked by FRT sites, and delivered the PCR products into R. solanacearum cells through natural transformation. Using this method, we knocked out the epsB and phcA genes, which are associated with exopolysaccharide (EPS) biosynthesis and regulation, respectively, in several R. solanacearum strains isolated from different host plants at a frequency from 5 (1E-08) to 45 (1E-08). To remove the antibiotic marker gene, the plasmid expressing the FLP enzyme was introduced into the above knockout mutants, which enabled removal of the marker gene. The effective combination of natural transformation and the FLP/FRT recombination system thus offers a simple and efficient method for functional study of putative virulence genes and for elucidation of R. solanacearum pathogenic mechanisms.
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Affiliation(s)
- Jinli Yan
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Nuoqiao Lin
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Xiaoqing Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Xuemei Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Huishan Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Qiqi Lin
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
| | - Xiaofan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Lianhui Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China
- *Correspondence: Lianhui Zhang,
| | - Lisheng Liao
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
- Lisheng Liao,
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Tano J, Ripa MB, Tondo ML, Carrau A, Petrocelli S, Rodriguez MV, Ferreira V, Siri MI, Piskulic L, Orellano EG. Light modulates important physiological features of Ralstonia pseudosolanacearum during the colonization of tomato plants. Sci Rep 2021; 11:14531. [PMID: 34267245 PMCID: PMC8282871 DOI: 10.1038/s41598-021-93871-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 06/25/2021] [Indexed: 02/06/2023] Open
Abstract
Ralstonia pseudosolanacearum GMI1000 (Rpso GMI1000) is a soil-borne vascular phytopathogen that infects host plants through the root system causing wilting disease in a wide range of agro-economic interest crops, producing economical losses. Several features contribute to the full bacterial virulence. In this work we study the participation of light, an important environmental factor, in the regulation of the physiological attributes and infectivity of Rpso GMI1000. In silico analysis of the Rpso genome revealed the presence of a Rsp0254 gene, which encodes a putative blue light LOV-type photoreceptor. We constructed a mutant strain of Rpso lacking the LOV protein and found that the loss of this protein and light, influenced characteristics involved in the pathogenicity process such as motility, adhesion and the biofilms development, which allows the successful host plant colonization, rendering bacterial wilt. This protein could be involved in the adaptive responses to environmental changes. We demonstrated that light sensing and the LOV protein, would be used as a location signal in the host plant, to regulate the expression of several virulence factors, in a time and tissue dependent way. Consequently, bacteria could use an external signal and Rpsolov gene to know their location within plant tissue during the colonization process.
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Affiliation(s)
- Josefina Tano
- Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas (IBR-FBIOyF), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario (CONICET-UNR), Suipacha 531, S2002LRK, Rosario, Argentina
| | - María Belén Ripa
- Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas (IBR-FBIOyF), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario (CONICET-UNR), Suipacha 531, S2002LRK, Rosario, Argentina
| | - María Laura Tondo
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Analía Carrau
- Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas (IBR-FBIOyF), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario (CONICET-UNR), Suipacha 531, S2002LRK, Rosario, Argentina
| | - Silvana Petrocelli
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - María Victoria Rodriguez
- Área Biología Vegetal, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Virginia Ferreira
- Área Microbiología, Departamento de Biociencias, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - María Inés Siri
- Área Microbiología, Departamento de Biociencias, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Laura Piskulic
- Área Estadística y Procesamiento de datos, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Elena Graciela Orellano
- Instituto de Biología Molecular y Celular de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas (IBR-FBIOyF), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario (CONICET-UNR), Suipacha 531, S2002LRK, Rosario, Argentina.
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7
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Freel KC, Fouteau S, Roche D, Farasin J, Huber A, Koechler S, Peres M, Chiboub O, Varet H, Proux C, Deschamps J, Briandet R, Torchet R, Cruveiller S, Lièvremont D, Coppée JY, Barbe V, Arsène-Ploetze F. Effect of arsenite and growth in biofilm conditions on the evolution of Thiomonas sp. CB2. Microb Genom 2020; 6:mgen000447. [PMID: 33034553 PMCID: PMC7660254 DOI: 10.1099/mgen.0.000447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 09/14/2020] [Indexed: 11/30/2022] Open
Abstract
Thiomonas bacteria are ubiquitous at acid mine drainage sites and play key roles in the remediation of water at these locations by oxidizing arsenite to arsenate, favouring the sorption of arsenic by iron oxides and their coprecipitation. Understanding the adaptive capacities of these bacteria is crucial to revealing how they persist and remain active in such extreme conditions. Interestingly, it was previously observed that after exposure to arsenite, when grown in a biofilm, some strains of Thiomonas bacteria develop variants that are more resistant to arsenic. Here, we identified the mechanisms involved in the emergence of such variants in biofilms. We found that the percentage of variants generated increased in the presence of high concentrations of arsenite (5.33 mM), especially in the detached cells after growth under biofilm-forming conditions. Analysis of gene expression in the parent strain CB2 revealed that genes involved in DNA repair were upregulated in the conditions where variants were observed. Finally, we assessed the phenotypes and genomes of the subsequent variants generated to evaluate the number of mutations compared to the parent strain. We determined that multiple point mutations accumulated after exposure to arsenite when cells were grown under biofilm conditions. Some of these mutations were found in what is referred to as ICE19, a genomic island (GI) carrying arsenic-resistance genes, also harbouring characteristics of an integrative and conjugative element (ICE). The mutations likely favoured the excision and duplication of this GI. This research aids in understanding how Thiomonas bacteria adapt to highly toxic environments, and, more generally, provides a window to bacterial genome evolution in extreme environments.
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Affiliation(s)
- Kelle C. Freel
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
- Present address: Hawaiʻi Institute of Marine Biology, University of Hawaiʻi at Mānoa, Kāneʻohe, HI, USA
| | - Stephanie Fouteau
- Génomique Métabolique, Genoscope, Institut de Biologie François Jacob, Commissariat à l'Energie Atomique (CEA), CNRS, Université Evry, Université Paris-Saclay, Evry, France
| | - David Roche
- Génomique Métabolique, Genoscope, Institut de Biologie François Jacob, Commissariat à l'Energie Atomique (CEA), CNRS, Université Evry, Université Paris-Saclay, Evry, France
| | - Julien Farasin
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
| | - Aline Huber
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
| | - Sandrine Koechler
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
- Present address: Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Martina Peres
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
| | - Olfa Chiboub
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
| | - Hugo Varet
- Plateforme Transcriptome et Epigenome, BioMics, Centre de Ressources et Recherches Technologiques, Institut Pasteur, Paris, France
- Hub Bioinformatique et Biostatistique, Centre de Bioinformatique, Biostatistique et Biologie Intégrative (C3BI, USR 3756, IP CNRS), Institut Pasteur, Paris, France
| | - Caroline Proux
- Plateforme Transcriptome et Epigenome, BioMics, Centre de Ressources et Recherches Technologiques, Institut Pasteur, Paris, France
| | - Julien Deschamps
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Romain Briandet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Rachel Torchet
- Génomique Métabolique, Genoscope, Institut de Biologie François Jacob, Commissariat à l'Energie Atomique (CEA), CNRS, Université Evry, Université Paris-Saclay, Evry, France
| | - Stephane Cruveiller
- Génomique Métabolique, Genoscope, Institut de Biologie François Jacob, Commissariat à l'Energie Atomique (CEA), CNRS, Université Evry, Université Paris-Saclay, Evry, France
| | - Didier Lièvremont
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
| | - Jean-Yves Coppée
- Plateforme Transcriptome et Epigenome, BioMics, Centre de Ressources et Recherches Technologiques, Institut Pasteur, Paris, France
| | - Valérie Barbe
- Génomique Métabolique, Genoscope, Institut de Biologie François Jacob, Commissariat à l'Energie Atomique (CEA), CNRS, Université Evry, Université Paris-Saclay, Evry, France
| | - Florence Arsène-Ploetze
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Institut de Botanique, CNRS – Université de Strasbourg, Strasbourg, France
- Present address: Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
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8
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Abstract
Twitching and swimming are two bacterial movements governed by pili and flagella. The present work identifies for the first time in the Gram-negative plant pathogen Ralstonia solanacearum a pilus-mediated chemotaxis pathway analogous to that governing flagellum-mediated chemotaxis. We show that regulatory genes in this pathway control all of the phenotypes related to pili, including twitching motility, natural transformation, and biofilm formation, and are also directly implicated in virulence, mainly during the first steps of the plant infection. Our results show that pili have a higher impact than flagella on the interaction of R. solanacearum with tomato plants and reveal new types of cross-talk between the swimming and twitching motility phenotypes: enhanced swimming in bacteria lacking pili and a role for the flagellum in root attachment. Ralstonia solanacearum is a bacterial plant pathogen causing important economic losses worldwide. In addition to the polar flagella responsible for swimming motility, this pathogen produces type IV pili (TFP) that govern twitching motility, a flagellum-independent movement on solid surfaces. The implication of chemotaxis in plant colonization, through the control flagellar rotation by the proteins CheW and CheA, has been previously reported in R. solanacearum. In this work, we have identified in this bacterium homologues of the Pseudomonas aeruginosapilI and chpA genes, suggested to play roles in TFP-associated motility analogous to those played by the cheW and cheA genes, respectively. We demonstrate that R. solanacearum strains with a deletion of the pilI or the chpA coding region show normal swimming and chemotaxis but altered biofilm formation and reduced twitching motility, transformation efficiency, and root attachment. Furthermore, these mutants displayed wild-type growth in planta and impaired virulence on tomato plants after soil-drench inoculations but not when directly applied to the xylem. Comparison with deletion mutants for pilA and fliC—encoding the major pilin and flagellin subunits, respectively—showed that both twitching and swimming are required for plant colonization and full virulence. This work proves for the first time the functionality of a pilus-mediated pathway encoded by pil-chp genes in R. solanacearum, demonstrating that pilI and chpA genes are bona fide motility regulators controlling twitching motility and its three related phenotypes: virulence, natural transformation, and biofilm formation. IMPORTANCE Twitching and swimming are two bacterial movements governed by pili and flagella. The present work identifies for the first time in the Gram-negative plant pathogen Ralstonia solanacearum a pilus-mediated chemotaxis pathway analogous to that governing flagellum-mediated chemotaxis. We show that regulatory genes in this pathway control all of the phenotypes related to pili, including twitching motility, natural transformation, and biofilm formation, and are also directly implicated in virulence, mainly during the first steps of the plant infection. Our results show that pili have a higher impact than flagella on the interaction of R. solanacearum with tomato plants and reveal new types of cross-talk between the swimming and twitching motility phenotypes: enhanced swimming in bacteria lacking pili and a role for the flagellum in root attachment.
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9
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Wu D, Schandry N, Lahaye T. A modular toolbox for Golden-Gate-based plasmid assembly streamlines the generation of Ralstonia solanacearum species complex knockout strains and multi-cassette complementation constructs. MOLECULAR PLANT PATHOLOGY 2018; 19:1511-1522. [PMID: 29077245 PMCID: PMC6638168 DOI: 10.1111/mpp.12632] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/02/2017] [Accepted: 10/22/2017] [Indexed: 05/15/2023]
Abstract
Members of the Ralstonia solanacearum species complex (Rssc) cause bacterial wilt, a devastating plant disease that affects numerous economically important crops. Like other bacterial pests, Rssc injects a cocktail of effector proteins via the bacterial type III secretion system into host cells that collectively promote disease. Given their functional relevance in disease, the identification of Rssc effectors and the investigation of their in planta function are likely to provide clues on how to generate pest-resistant crop plants. Accordingly, molecular analysis of effector function is a focus of Rssc research. The elucidation of effector function requires corresponding gene knockout strains or strains that express the desired effector variants. The cloning of DNA constructs that facilitate the generation of such strains has hindered the investigation of Rssc effectors. To overcome these limitations, we have designed, generated and functionally validated a toolkit consisting of DNA modules that can be assembled via Golden-Gate (GG) cloning into either desired gene knockout constructs or multi-cassette expression constructs. The Ralstonia-GG-kit is compatible with a previously established toolkit that facilitates the generation of DNA constructs for in planta expression. Accordingly, cloned modules, encoding effectors of interest, can be transferred to vectors for expression in Rssc strains and plant cells. As many effector genes have been cloned in the past as GATEWAY entry vectors, we have also established a conversion vector that allows the implementation of GATEWAY entry vectors into the Ralstonia-GG-kit. In summary, the Ralstonia-GG-kit provides a valuable tool for the genetic investigation of genes encoding effectors and other Rssc genes.
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Affiliation(s)
- Dousheng Wu
- Center for Plant Molecular Biology, Eberhard‐Karls‐University TübingenTübingen 72076Germany
| | - Niklas Schandry
- Center for Plant Molecular Biology, Eberhard‐Karls‐University TübingenTübingen 72076Germany
- Present address:
Gregor‐Mendel Institute of Molecular Plant Biology, Dr. Bohr Gasse 3Vienna 1030Austria
| | - Thomas Lahaye
- Center for Plant Molecular Biology, Eberhard‐Karls‐University TübingenTübingen 72076Germany
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10
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Perrier A, Barberis P, Genin S. Introduction of Genetic Material in Ralstonia solanacearum Through Natural Transformation and Conjugation. Methods Mol Biol 2018; 1734:201-207. [PMID: 29288456 DOI: 10.1007/978-1-4939-7604-1_16] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ralstonia solanacearum is a soil-borne plant pathogen, responsible of the bacterial wilt disease. Its unusual wide host range (more than 250 plant species), aggressiveness, and broad geographic distribution have made of this bacterium the main plant pathogenic model in the beta-Proteobacteria class. Many R. solanacearum strains have the ability to internalize exogenous DNA through natural transformation. This property is widely used in reverse genetics studies to create mutants or reporter gene constructs, in the aim to study the molecular bases of pathogenesis of this bacterium. In this chapter, we describe three in vitro methods (natural transformation, electrotransformation, and conjugation) commonly used to produce recombinant R. solanacearum cells after introduction of exogenous DNA.
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Affiliation(s)
- Anthony Perrier
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Patrick Barberis
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Stéphane Genin
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France.
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11
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Use of Natural Transformation To Establish an Easy Knockout Method in Riemerella anatipestifer. Appl Environ Microbiol 2017; 83:AEM.00127-17. [PMID: 28258143 DOI: 10.1128/aem.00127-17] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 02/22/2017] [Indexed: 01/08/2023] Open
Abstract
Riemerella anatipestifer is a member of the family Flavobacteriaceae and a major causative agent of duck serositis. Little is known about its genetics and pathogenesis. Several bacteria are competent for natural transformation; however, whether R. anatipestifer is also competent for natural transformation has not been investigated. Here, we showed that R. anatipestifer strain ATCC 11845 can uptake the chromosomal DNA of R. anatipestifer strain RA-CH-1 in all growth phases. Subsequently, a natural transformation-based knockout method was established for R. anatipestifer ATCC 11845. Targeted mutagenesis gave transformation frequencies of ∼10-5 transformants. Competition assay experiments showed that R. anatipestifer ATCC 11845 preferentially took up its own DNA rather than heterogeneous DNA, such as Escherichia coli DNA. Transformation was less efficient with the shuttle plasmid pLMF03 (transformation frequencies of ∼10-9 transformants). However, the efficiency of transformation was increased approximately 100-fold using pLMF03 derivatives containing R. anatipestifer DNA fragments (transformation frequencies of ∼10-7 transformants). Finally, we found that the R. anatipestifer RA-CH-1 strain was also naturally transformable, suggesting that natural competence is widely applicable for this species. The findings described here provide important tools for the genetic manipulation of R. anatipestiferIMPORTANCERiemerella anatipestifer is an important duck pathogen that belongs to the family Flavobacteriaceae At least 21 different serotypes have been identified. Genetic diversity has been demonstrated among these serotypes. The genetic and pathogenic mechanisms of R. anatipestifer remain largely unknown because no genetic tools are available for this bacterium. At present, natural transformation has been found in some bacteria but not in R. anatipestifer For the first time, we showed that natural transformation occurred in R. anatipestifer ATCC 11845 and R. anatipestifer RA-CH-1. Then, we established an easy gene knockout method in R. anatipestifer based on natural transformation. This information is important for further studies of the genetic diversity and pathogenesis in R. anatipestifer.
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12
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Barman A, Buragohain C, Ray SK. Disruption ofcomAhomolog inRalstonia solanacearumdoes not impair its twitching motility. J Basic Microbiol 2017; 57:218-227. [DOI: 10.1002/jobm.201600562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/17/2016] [Accepted: 12/29/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Anjan Barman
- Department of Molecular Biology and Biotechnology; Tezpur University; Tezpur Assam India
| | - Chandrika Buragohain
- Department of Molecular Biology and Biotechnology; Tezpur University; Tezpur Assam India
| | - Suvendra Kumar Ray
- Department of Molecular Biology and Biotechnology; Tezpur University; Tezpur Assam India
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13
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Li P, Wang D, Yan J, Zhou J, Deng Y, Jiang Z, Cao B, He Z, Zhang L. Genomic Analysis of Phylotype I Strain EP1 Reveals Substantial Divergence from Other Strains in the Ralstonia solanacearum Species Complex. Front Microbiol 2016; 7:1719. [PMID: 27833603 PMCID: PMC5080846 DOI: 10.3389/fmicb.2016.01719] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 10/13/2016] [Indexed: 11/13/2022] Open
Abstract
Ralstonia solanacearum species complex is a devastating group of phytopathogens with an unusually wide host range and broad geographical distribution. R. solanacearum isolates may differ considerably in various properties including host range and pathogenicity, but the underlying genetic bases remain vague. Here, we conducted the genome sequencing of strain EP1 isolated from Guangdong Province of China, which belongs to phylotype I and is highly virulent to a range of solanaceous crops. Its complete genome contains a 3.95-Mb chromosome and a 2.05-Mb mega-plasmid, which is considerably bigger than reported genomes of other R. solanacearum strains. Both the chromosome and the mega-plasmid have essential house-keeping genes and many virulence genes. Comparative analysis of strain EP1 with other 3 phylotype I and 3 phylotype II, III, IV strains unveiled substantial genome rearrangements, insertions and deletions. Genome sequences are relatively conserved among the 4 phylotype I strains, but more divergent among strains of different phylotypes. Moreover, the strains exhibited considerable variations in their key virulence genes, including those encoding secretion systems and type III effectors. Our results provide valuable information for further elucidation of the genetic basis of diversified virulences and host range of R. solanacearum species.
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Affiliation(s)
- Peng Li
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural University Guangzhou, China
| | - Dechen Wang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural University Guangzhou, China
| | - Jinli Yan
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural University Guangzhou, China
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural University Guangzhou, China
| | - Yinyue Deng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural UniversityGuangzhou, China; Guangdong Innovative and Entepreneurial Research Team of Sociomicrobiology Basic Science and Frontier Technology, College of Agriculture, South China Agricultural UniversityGuangzhou, China
| | - Zide Jiang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural University Guangzhou, China
| | - Bihao Cao
- Department of Vegetables, College of Horticulture, South China Agricultural University Guangzhou, China
| | - Zifu He
- Plant Protection Research Institute Guangdong Academy of Agriculture Sciences Guangzhou, China
| | - Lianhui Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, College of Agriculture, South China Agricultural UniversityGuangzhou, China; Institute of Molecular and Cell BiologySingapore, Singapore
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14
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Kandel PP, Lopez SM, Almeida RPP, De La Fuente L. Natural Competence of Xylella fastidiosa Occurs at a High Frequency Inside Microfluidic Chambers Mimicking the Bacterium's Natural Habitats. Appl Environ Microbiol 2016; 82:5269-77. [PMID: 27316962 PMCID: PMC4988197 DOI: 10.1128/aem.01412-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/13/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Xylella fastidiosa is a xylem-limited bacterium that is the causal agent of emerging diseases in a number of economically important crops. Genetic diversity studies have demonstrated homologous recombination occurring among X. fastidiosa strains, which has been proposed to contribute to host plant shifts. Moreover, experimental evidence confirmed that X. fastidiosa is naturally competent for recombination in vitro Here, as an approximation of natural habitats (plant xylem vessels and insect mouthparts), recombination was studied in microfluidic chambers (MCs) filled with media amended with grapevine xylem sap. First, different media were screened for recombination in solid agar plates using a pair of X. fastidiosa strains that were previously reported to recombine in coculture. The highest frequency of recombination was obtained with PD3 medium, compared to those with the other two media (X. fastidiosa medium [XFM] and periwinkle wilt [PW] medium) used in previous studies. Dissection of the media components led to the identification of bovine serum albumin as an inhibitor of recombination that was correlated to its previously known effect on inhibition of twitching motility. When recombination was performed in liquid culture, the frequencies were significantly higher under flow conditions (MCs) than under batch conditions (test tubes). The recombination frequencies in MCs and agar plates were not significantly different from each other. Grapevine xylem sap from both susceptible and tolerant varieties allowed high recombination frequency in MCs when mixed with PD3. These results suggest that X. fastidiosa has the ability to be naturally competent in the natural growth environment of liquid flow, and this phenomenon could have implications in X. fastidiosa environmental adaptation. IMPORTANCE Xylella fastidiosa is a plant pathogen that lives inside xylem vessels (where water and nutrients are transported inside the plant) and the mouthparts of insect vectors. This bacterium causes emerging diseases in various crops worldwide, including recent outbreaks in Europe. The mechanisms by which this bacterium adapts to new hosts is not understood, but it was previously shown that it is naturally competent, meaning that it can take up DNA from the environment and incorporate it into its genome (recombination). In this study, we show that the frequency of recombination is highest when the bacterium is grown under flow conditions in microfluidic chambers modeled after its natural habitats, and recombination was still high when the medium was amended with grapevine sap. Our results suggest that this bacterium is able to recombine when growing inside plants or insects, and this can be a mechanism of adaptation of this pathogen that causes incurable diseases.
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Affiliation(s)
- Prem P Kandel
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Samantha M Lopez
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Rodrigo P P Almeida
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California, USA
| | - Leonardo De La Fuente
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
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15
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Minh Tran T, MacIntyre A, Khokhani D, Hawes M, Allen C. Extracellular DNases of Ralstonia solanacearum modulate biofilms and facilitate bacterial wilt virulence. Environ Microbiol 2016; 18:4103-4117. [PMID: 27387368 DOI: 10.1111/1462-2920.13446] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 07/01/2016] [Indexed: 12/21/2022]
Abstract
Ralstonia solanacearum is a soil-borne vascular pathogen that colonizes plant xylem vessels, a flowing, low-nutrient habitat where biofilms could be adaptive. Ralstonia solanacearum forms biofilm in vitro, but it was not known if the pathogen benefits from biofilms during infection. Scanning electron microscopy revealed that during tomato infection, R. solanacearum forms biofilm-like masses in xylem vessels. These aggregates contain bacteria embedded in a matrix including chromatin-like fibres commonly observed in other bacterial biofilms. Chemical and enzymatic assays demonstrated that the bacterium releases extracellular DNA in culture and that DNA is an integral component of the biofilm matrix. An R. solanacearum mutant lacking the pathogen's two extracellular nucleases (exDNases) formed non-spreading colonies and abnormally thick biofilms in vitro. The biofilms formed by the exDNase mutant in planta contained more and thicker fibres. This mutant was also reduced in virulence on tomato plants and did not spread in tomato stems as well as the wild-type strain, suggesting that these exDNases facilitate biofilm maturation and bacterial dispersal. To our knowledge, this is the first demonstration that R. solanacearum forms biofilms in plant xylem vessels, and the first documentation that plant pathogens use DNases to modulate their biofilm structure for systemic spread and virulence.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, 53706, USA.,Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Devanshi Khokhani
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, AZ, 85721, USA
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, 53706, USA
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16
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Fink R, Moran E. Biosafety for Large-Scale Containment Level 1 Operations Using Recombinant DNA Technology: No Emerging Hazards. APPLIED BIOSAFETY 2016. [DOI: 10.1177/153567600501000104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Richard Fink
- Wyeth BioPharma, Andover, Massachussetts and 2Wyeth Medica Ireland, Clondalkin, Dublin, Repulic of Ireland
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17
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Tran TM, MacIntyre A, Hawes M, Allen C. Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum. PLoS Pathog 2016; 12:e1005686. [PMID: 27336156 PMCID: PMC4919084 DOI: 10.1371/journal.ppat.1005686] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/18/2016] [Indexed: 12/21/2022] Open
Abstract
Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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18
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Tran TM, MacIntyre A, Hawes M, Allen C. Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum. PLoS Pathog 2016; 12:e1005686. [PMID: 27336156 DOI: 10.1371/journal.ppat.10056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/18/2016] [Indexed: 05/22/2023] Open
Abstract
Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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19
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Wang K, Remigi P, Anisimova M, Lonjon F, Kars I, Kajava A, Li CH, Cheng CP, Vailleau F, Genin S, Peeters N. Functional assignment to positively selected sites in the core type III effector RipG7 from Ralstonia solanacearum. MOLECULAR PLANT PATHOLOGY 2016; 17:553-64. [PMID: 26300048 PMCID: PMC6638336 DOI: 10.1111/mpp.12302] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The soil-borne pathogen Ralstonia solanacearum causes bacterial wilt in a broad range of plants. The main virulence determinants of R. solanacearum are the type III secretion system (T3SS) and its associated type III effectors (T3Es), translocated into the host cells. Of the conserved T3Es among R. solanacearum strains, the Fbox protein RipG7 is required for R. solanacearum pathogenesis on Medicago truncatula. In this work, we describe the natural ripG7 variability existing in the R. solanacearum species complex. We show that eight representative ripG7 orthologues have different contributions to pathogenicity on M. truncatula: only ripG7 from Asian or African strains can complement the absence of ripG7 in GMI1000 (Asian reference strain). Nonetheless, RipG7 proteins from American and Indonesian strains can still interact with M. truncatula SKP1-like/MSKa protein, essential for the function of RipG7 in virulence. This indicates that the absence of complementation is most likely a result of the variability in the leucine-rich repeat (LRR) domain of RipG7. We identified 11 sites under positive selection in the LRR domains of RipG7. By studying the functional impact of these 11 sites, we show the contribution of five positively selected sites for the function of RipG7CMR15 in M. truncatula colonization. This work reveals the genetic and functional variation of the essential core T3E RipG7 from R. solanacearum. This analysis is the first of its kind on an essential disease-controlling T3E, and sheds light on the co-evolutionary arms race between the bacterium and its hosts.
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Affiliation(s)
- Keke Wang
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
| | - Philippe Remigi
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
| | - Maria Anisimova
- Institute of Applied Simulations, School of Life Sciences and Facility Management, Zürich University of Applied Sciences, Gruenalstrasse 14, 8820, Wädesnwil, Switzerland
| | - Fabien Lonjon
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
| | - Ilona Kars
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
| | - Andrey Kajava
- Centre de Recherche de Biochimie Macromoléculaire, CNRS, UMR5237, 1919 Route de Mende, 34000, Montpellier, France
| | - Chien-Hui Li
- Institute of Plant Biology, National Taiwan University, Taipei, 11529, Taiwan, R.O.C
| | - Chiu-Ping Cheng
- Institute of Plant Biology, National Taiwan University, Taipei, 11529, Taiwan, R.O.C
| | - Fabienne Vailleau
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- Université de Toulouse, INP, ENSAT, 18 Chemin de Borde Rouge, Castanet-Tolosan, 31326, France
| | - Stéphane Genin
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
| | - Nemo Peeters
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR441, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR2594, CS52627 Chemin de Borde Rouge, 31326, Castanet-Tolosan, France
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Nishat S, Hamim I, Khalil MI, Ali MA, Hossain MA, Meah MB, Islam MR. Genetic diversity of the bacterial wilt pathogen Ralstonia solanacearum using a RAPD marker. C R Biol 2015; 338:757-67. [PMID: 26302834 DOI: 10.1016/j.crvi.2015.06.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/06/2015] [Accepted: 06/09/2015] [Indexed: 11/27/2022]
Abstract
Bacterial wilt caused by Ralstonia solanacearum is a destructive disease of many economically important crop species. A significant variation in wilt incidence and severity in eggplant and potato was observed among the growing areas surveyed. R. solanacearum isolates obtained both from eggplant and potato belong to biovar III, while isolates from eggplant belong to race 1 and isolates obtained from potato belong to race 3. Random amplified polymorphic DNA (RAPD) technique was used as a tool for assessing genetic variation and relationship among seven isolate groups of R. solanacearum viz., RsB-1, RsB-2, RsB-3, RsP-1, RsP-2, RsP-3 and RsP-4, consisting in a total of 28 isolates. Out of the RAPD markers used, amplification with four decamer primers produced 70 bands with sizes ranging from 100 to 1400 bp. Out of 70 bands, 68 bands (97.06%) were polymorphic and two bands (2.94%) were monomorphic amongst the seven R. solanacearum isolates group. The Unweighted Pair Group Method of Arithmetic Means (UPGMA) dendrogram constructed from Nei's genetic distance produced two main clusters of the seven isolates of R. solanacearum. The isolates RsB-1, RsB-2, RsB-3 and R-4 grouped in cluster І, while RsP-2, RsP-3 and RsP-4 grouped in cluster ІІ. The highest intra-variety similarity index (Si) was found in RsB-1 isolate (86.35%) and the lowest one in RsP-2 (56.59%). The results indicated that relatively higher and lower levels of genetic variation were found in RsP-3 and RsB-3, respectively. The coefficient of gene differentiation (G(st)) was 0.5487, reflecting the existence of a high level of genetic variations among seven isolates of R. solanacearum. Comparatively higher genetic distance (0.4293) and lower genetic identity (0.6510) were observed between RsB-2 and RsP-4 combinations. The lowest genetic distance (0.0357) and highest genetic identity (0.9650) were found in RsB-1 vs. RsB-2 pair. Thus, RAPD offers a potentially simple, rapid and reliable method to evaluate genetic diversity analysis in R. solanacearum.
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Affiliation(s)
- Sayeda Nishat
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
| | - Islam Hamim
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
| | - M Ibrahim Khalil
- Plant Pathology Division, Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh
| | - Md Ayub Ali
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
| | - Muhammed Ali Hossain
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
| | - M Bahadur Meah
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
| | - Md Rashidul Islam
- Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
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Efficient Genome Editing in Clostridium cellulolyticum via CRISPR-Cas9 Nickase. Appl Environ Microbiol 2015; 81:4423-31. [PMID: 25911483 DOI: 10.1128/aem.00873-15] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 04/16/2015] [Indexed: 02/01/2023] Open
Abstract
The CRISPR-Cas9 system is a powerful and revolutionary genome-editing tool for eukaryotic genomes, but its use in bacterial genomes is very limited. Here, we investigated the use of the Streptococcus pyogenes CRISPR-Cas9 system in editing the genome of Clostridium cellulolyticum, a model microorganism for bioenergy research. Wild-type Cas9-induced double-strand breaks were lethal to C. cellulolyticum due to the minimal expression of nonhomologous end joining (NHEJ) components in this strain. To circumvent this lethality, Cas9 nickase was applied to develop a single-nick-triggered homologous recombination strategy, which allows precise one-step editing at intended genomic loci by transforming a single vector. This strategy has a high editing efficiency (>95%) even using short homologous arms (0.2 kb), is able to deliver foreign genes into the genome in a single step without a marker, enables precise editing even at two very similar target sites differing by two bases preceding the seed region, and has a very high target site density (median interval distance of 9 bp and 95.7% gene coverage in C. cellulolyticum). Together, these results establish a simple and robust methodology for genome editing in NHEJ-ineffective prokaryotes.
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Ailloud F, Lowe T, Cellier G, Roche D, Allen C, Prior P. Comparative genomic analysis of Ralstonia solanacearum reveals candidate genes for host specificity. BMC Genomics 2015; 16:270. [PMID: 25888333 PMCID: PMC4396162 DOI: 10.1186/s12864-015-1474-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 03/20/2015] [Indexed: 12/02/2022] Open
Abstract
Background Ralstonia solanacearum is a vascular soil-borne plant pathogen with an unusually broad host range. This economically destructive and globally distributed bacterium has thousands of distinct lineages within a heterogeneous and taxonomically disputed species complex. Some lineages include highly host-adapted strains (ecotypes), such as the banana Moko disease-causing strains, the cold-tolerant potato brown rot strains (also known as R3bv2) and the recently emerged Not Pathogenic to Banana (NPB) strains. Results These distinct ecotypes offer a robust model to study host adaptation and the emergence of ecotypes because the polyphyletic Moko strains include lineages that are phylogenetically close to the monophyletic brown rot and NPB strains. Draft genomes of eight new strains belonging to these three model ecotypes were produced to complement the eleven publicly available R. solanacearum genomes. Using a suite of bioinformatics methods, we searched for genetic and evolutionary features that distinguish ecotypes and propose specific hypotheses concerning mechanisms of host adaptation in the R. solanacearum species complex. Genome-wide, few differences were identified, but gene loss events, non-synonymous polymorphisms, and horizontal gene transfer were identified among type III effectors and were associated with host range differences. Conclusions This extensive comparative genomics analysis uncovered relatively few divergent features among closely related strains with contrasting biological characteristics; however, several virulence factors were associated with the emergence of Moko, NPB and brown rot and could explain host adaptation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1474-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Florent Ailloud
- CIRAD, UMR PVBMT, F-97410, Saint-Pierre, La Réunion, France. .,Anses - Plant Health Laboratory, F-97410, Saint-Pierre, La Réunion, France.
| | - Tiffany Lowe
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Gilles Cellier
- Anses - Plant Health Laboratory, F-97410, Saint-Pierre, La Réunion, France.
| | - David Roche
- Institut de Génomique, Genoscope, Commissariat à l'Energie Atomique (CEA), Evry, Paris, France.
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Philippe Prior
- CIRAD, UMR PVBMT, F-97410, Saint-Pierre, La Réunion, France. .,Département de Santé des Plantes et Environnement, (SPE) Inra, Paris, France.
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Ailloud F, Lowe T, Cellier G, Roche D, Allen C, Prior P. Comparative genomic analysis of Ralstonia solanacearum reveals candidate genes for host specificity. BMC Genomics 2015. [PMID: 25888333 DOI: 10.1186/s12864-015-1474-1478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
Abstract
BACKGROUND Ralstonia solanacearum is a vascular soil-borne plant pathogen with an unusually broad host range. This economically destructive and globally distributed bacterium has thousands of distinct lineages within a heterogeneous and taxonomically disputed species complex. Some lineages include highly host-adapted strains (ecotypes), such as the banana Moko disease-causing strains, the cold-tolerant potato brown rot strains (also known as R3bv2) and the recently emerged Not Pathogenic to Banana (NPB) strains. RESULTS These distinct ecotypes offer a robust model to study host adaptation and the emergence of ecotypes because the polyphyletic Moko strains include lineages that are phylogenetically close to the monophyletic brown rot and NPB strains. Draft genomes of eight new strains belonging to these three model ecotypes were produced to complement the eleven publicly available R. solanacearum genomes. Using a suite of bioinformatics methods, we searched for genetic and evolutionary features that distinguish ecotypes and propose specific hypotheses concerning mechanisms of host adaptation in the R. solanacearum species complex. Genome-wide, few differences were identified, but gene loss events, non-synonymous polymorphisms, and horizontal gene transfer were identified among type III effectors and were associated with host range differences. CONCLUSIONS This extensive comparative genomics analysis uncovered relatively few divergent features among closely related strains with contrasting biological characteristics; however, several virulence factors were associated with the emergence of Moko, NPB and brown rot and could explain host adaptation.
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Affiliation(s)
- Florent Ailloud
- CIRAD, UMR PVBMT, F-97410, Saint-Pierre, La Réunion, France.
- Anses - Plant Health Laboratory, F-97410, Saint-Pierre, La Réunion, France.
| | - Tiffany Lowe
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Gilles Cellier
- Anses - Plant Health Laboratory, F-97410, Saint-Pierre, La Réunion, France.
| | - David Roche
- Institut de Génomique, Genoscope, Commissariat à l'Energie Atomique (CEA), Evry, Paris, France.
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Philippe Prior
- CIRAD, UMR PVBMT, F-97410, Saint-Pierre, La Réunion, France.
- Département de Santé des Plantes et Environnement, (SPE) Inra, Paris, France.
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Ralstonia solanacearum uses inorganic nitrogen metabolism for virulence, ATP production, and detoxification in the oxygen-limited host xylem environment. mBio 2015; 6:e02471. [PMID: 25784703 PMCID: PMC4453514 DOI: 10.1128/mbio.02471-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Genomic data predict that, in addition to oxygen, the bacterial plant pathogen Ralstonia solanacearum can use nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), and nitrous oxide (N2O) as terminal electron acceptors (TEAs). Genes encoding inorganic nitrogen reduction were highly expressed during tomato bacterial wilt disease, when the pathogen grows in xylem vessels. Direct measurements found that tomato xylem fluid was low in oxygen, especially in plants infected by R. solanacearum. Xylem fluid contained ~25 mM NO3−, corresponding to R. solanacearum’s optimal NO3− concentration for anaerobic growth in vitro. We tested the hypothesis that R. solanacearum uses inorganic nitrogen species to respire and grow during pathogenesis by making deletion mutants that each lacked a step in nitrate respiration (ΔnarG), denitrification (ΔaniA, ΔnorB, and ΔnosZ), or NO detoxification (ΔhmpX). The ΔnarG, ΔaniA, and ΔnorB mutants grew poorly on NO3− compared to the wild type, and they had reduced adenylate energy charge levels under anaerobiosis. While NarG-dependent NO3− respiration directly enhanced growth, AniA-dependent NO2− reduction did not. NO2− and NO inhibited growth in culture, and their removal depended on denitrification and NO detoxification. Thus, NO3− acts as a TEA, but the resulting NO2− and NO likely do not. None of the mutants grew as well as the wild type in planta, and strains lacking AniA (NO2− reductase) or HmpX (NO detoxification) had reduced virulence on tomato. Thus, R. solanacearum exploits host NO3− to respire, grow, and cause disease. Degradation of NO2− and NO is also important for successful infection and depends on denitrification and NO detoxification systems. The plant-pathogenic bacterium Ralstonia solanacearum causes bacterial wilt, one of the world’s most destructive crop diseases. This pathogen’s explosive growth in plant vascular xylem is poorly understood. We used biochemical and genetic approaches to show that R. solanacearum rapidly depletes oxygen in host xylem but can then respire using host nitrate as a terminal electron acceptor. The microbe uses its denitrification pathway to detoxify the reactive nitrogen species nitrite (a product of nitrate respiration) and nitric oxide (a plant defense signal). Detoxification may play synergistic roles in bacterial wilt virulence by converting the host’s chemical weapon into an energy source. Mutant bacterial strains lacking elements of the denitrification pathway could not grow as well as the wild type in tomato plants, and some mutants were also reduced in virulence. Our results show how a pathogen’s metabolic activity can alter the host environment in ways that increase pathogen success.
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Siri MI, Sanabria A, Boucher C, Pianzzola MJ. New type IV pili-related genes involved in early stages of Ralstonia solanacearum potato infection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:712-24. [PMID: 24625029 DOI: 10.1094/mpmi-07-13-0210-r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
This study provides insights into the pathogenesis of Ralstonia solanacearum, in particular with regards to strains belonging to phylotype IIB, sequevar 1 (IIB-1) and their interaction with potato, its natural host. We performed a comparative genomic analysis among IIB-1 R. solanacearum strains with different levels of virulence in order to identify candidate virulence genes. With this approach, we identified a 33.7-kb deletion in a strain showing reduced virulence on potato. This region contains a cluster of six genes putatively involved in type IV pili (Tfp) biogenesis. Functional analysis suggests that these proteins contribute to several Tfp-related functions such as twitching motility and biofilm formation. In addition, this genetic cluster was found to contribute to early bacterial wilt pathogenesis and colonization fitness of potato roots.
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Pauly J, Spiteller D, Linz J, Jacobs J, Allen C, Nett M, Hoffmeister D. Ralfuranone Thioether Production by the Plant PathogenRalstonia solanacearum. Chembiochem 2013; 14:2169-78. [DOI: 10.1002/cbic.201300364] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Indexed: 12/18/2022]
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Lefeuvre P, Cellier G, Remenant B, Chiroleu F, Prior P. Constraints on genome dynamics revealed from gene distribution among the Ralstonia solanacearum species. PLoS One 2013; 8:e63155. [PMID: 23723974 PMCID: PMC3665557 DOI: 10.1371/journal.pone.0063155] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 03/28/2013] [Indexed: 01/11/2023] Open
Abstract
Because it is suspected that gene content may partly explain host adaptation and ecology of pathogenic bacteria, it is important to study factors affecting genome composition and its evolution. While recent genomic advances have revealed extremely large pan-genomes for some bacterial species, it remains difficult to predict to what extent gene pool is accessible within or transferable between populations. As genomes bear imprints of the history of the organisms, gene distribution pattern analyses should provide insights into the forces and factors at play in the shaping and maintaining of bacterial genomes. In this study, we revisited the data obtained from a previous CGH microarrays analysis in order to assess the genomic plasticity of the R. solanacearum species complex. Gene distribution analyses demonstrated the remarkably dispersed genome of R. solanacearum with more than half of the genes being accessory. From the reconstruction of the ancestral genomes compositions, we were able to infer the number of gene gain and loss events along the phylogeny. Analyses of gene movement patterns reveal that factors associated with gene function, genomic localization and ecology delineate gene flow patterns. While the chromosome displayed lower rates of movement, the megaplasmid was clearly associated with hot-spots of gene gain and loss. Gene function was also confirmed to be an essential factor in gene gain and loss dynamics with significant differences in movement patterns between different COG categories. Finally, analyses of gene distribution highlighted possible highways of horizontal gene transfer. Due to sampling and design bias, we can only speculate on factors at play in this gene movement dynamic. Further studies examining precise conditions that favor gene transfer would provide invaluable insights in the fate of bacteria, species delineation and the emergence of successful pathogens.
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Affiliation(s)
- Pierre Lefeuvre
- CIRAD UMR Peuplements Végétaux et Bioagresseurs en Milieu Tropical, CIRAD-Université de la Réunion, Pôle de Protection des Plantes, Saint Pierre, La Réunion, France.
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Varani AM, Monteiro-Vitorello CB, Nakaya HI, Van Sluys MA. The role of prophage in plant-pathogenic bacteria. ANNUAL REVIEW OF PHYTOPATHOLOGY 2013; 51:429-451. [PMID: 23725471 DOI: 10.1146/annurev-phyto-081211-173010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A diverse set of phage lineages is associated with the bacterial plant-pathogen genomes sequenced to date. Analysis of 37 genomes revealed 5,169 potential genes (approximately 4.3 Mbp) of phage origin, and at least 50% had no function assigned or are nonessential to phage biology. Some phytopathogens have transcriptionally active prophage genes under conditions that mimic plant infection, suggesting an association between plant disease and prophage transcriptional modulation. The role of prophages within genomes for cell biology varies. For pathogens such as Pectobacterium, Pseudomonas, Ralstonia, and Streptomyces, involvement of prophage in disease symptoms has been demonstrated. In Xylella and Xanthomonas, prophage activity is associated with genome rearrangements and strain differentiation. For other pathogens, prophage roles are yet to be established. This review integrates available information in a unique interface ( http://propnav.esalq.usp.br ) that may be assessed to improve research in prophage biology and its association with genome evolution and pathogenicity.
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Affiliation(s)
- Alessandro M Varani
- Departamento de Genética (LGN), Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, 13418-900 Piracicaba/SP, Brazil
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Kung SH, Retchless AC, Kwan JY, Almeida RPP. Effects of DNA size on transformation and recombination efficiencies in Xylella fastidiosa. Appl Environ Microbiol 2013; 79:1712-7. [PMID: 23315739 PMCID: PMC3591940 DOI: 10.1128/aem.03525-12] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 01/02/2013] [Indexed: 11/20/2022] Open
Abstract
Horizontally transferred DNA acquired through transformation and recombination has the potential to contribute to the diversity and evolution of naturally competent bacteria. However, many different factors affect the efficiency with which DNA can be transformed and recombined. In this study, we determined how the size of both homologous and nonhomologous regions affects transformation and recombination efficiencies in Xylella fastidiosa, a naturally competent generalist pathogen responsible for many emerging plant diseases. Our experimental data indicate that 96 bp of flanking homology is sufficient to initiate recombination, with recombination efficiencies increasing exponentially with the size of the homologous flanking region up to 1 kb. Recombination efficiencies also decreased with the size of the nonhomologous insert, with no recombination detected when 6 kb of nonhomologous DNA was flanked on either side by 1 kb of homologous sequences. Upon analyzing sequenced X. fastidiosa subsp. fastidiosa genomes for evidence of allele conversion, we estimated the mean size of recombination events to be 1,906 bp, with each event modifying, on average, 1.79% of the nucleotides in the recombined region. There is increasing evidence that horizontally acquired genes significantly affect the genetic diversity of X. fastidiosa, and DNA acquired through natural transformation could be a prominent mode of this horizontal transfer.
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Affiliation(s)
| | - Adam C. Retchless
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Jessica Y. Kwan
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Rodrigo P. P. Almeida
- Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
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Wang X, Liu X, Han H. Evaluation of antibacterial effects of carbon nanomaterials against copper-resistant Ralstonia solanacearum. Colloids Surf B Biointerfaces 2013. [DOI: 10.1016/j.colsurfb.2012.09.044] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Seitz P, Blokesch M. Cues and regulatory pathways involved in natural competence and transformation in pathogenic and environmental Gram-negative bacteria. FEMS Microbiol Rev 2012; 37:336-63. [PMID: 22928673 DOI: 10.1111/j.1574-6976.2012.00353.x] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 07/27/2012] [Accepted: 08/21/2012] [Indexed: 12/23/2022] Open
Abstract
Bacterial genomics is flourishing, as whole-genome sequencing has become affordable, readily available and rapid. As a result, it has become clear how frequently horizontal gene transfer (HGT) occurs in bacteria. The potential implications are highly significant because HGT contributes to several processes, including the spread of antibiotic-resistance cassettes, the distribution of toxin-encoding phages and the transfer of pathogenicity islands. Three modes of HGT are recognized in bacteria: conjugation, transduction and natural transformation. In contrast to the first two mechanisms, natural competence for transformation does not rely on mobile genetic elements but is driven solely by a developmental programme in the acceptor bacterium. Once the bacterium becomes competent, it is able to take up DNA from the environment and to incorporate the newly acquired DNA into its own chromosome. The initiation and duration of competence differ significantly among bacteria. In this review, we outline the latest data on representative naturally transformable Gram-negative bacteria and how their competence windows differ. We also summarize how environmental cues contribute to the initiation of competence in a subset of naturally transformable Gram-negative bacteria and how the complexity of the niche might dictate the fine-tuning of the competence window.
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Affiliation(s)
- Patrick Seitz
- Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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Monteiro F, Solé M, van Dijk I, Valls M. A chromosomal insertion toolbox for promoter probing, mutant complementation, and pathogenicity studies in Ralstonia solanacearum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:557-68. [PMID: 22122329 DOI: 10.1094/mpmi-07-11-0201] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We describe here the construction of a delivery system for stable and directed insertion of gene constructs in a permissive chromosomal site of the bacterial wilt pathogen Ralstonia solanacearum. The system consists of a collection of suicide vectors-the Ralstonia chromosome (pRC) series-that carry an integration element flanked by transcription terminators and two sequences of homology to the chromosome of strain GMI1000, where the integration element is inserted through a double recombination event. Unique restriction enzyme sites and a GATEWAY cassette enable cloning of any promoter::gene combination in the integration element. Variants endowed with different selectable antibiotic resistance genes and promoter::gene combinations are described. We show that the system can be readily used in GMI1000 and adapted to other R. solanacearum strains using an accessory plasmid. We prove that the pRC system can be employed to complement a deletion mutation with a single copy of the native gene, and to measure transcription of selected promoters in monocopy both in vitro and in planta. Finally, the system has been used to purify and study secretion type III effectors. These novel genetic tools will be particularly useful for the construction of recombinant bacteria that maintain inserted genes or reporter fusions in competitive situations (i.e., during plant infection).
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Affiliation(s)
- Freddy Monteiro
- Deptartament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645 annex, 08028 Barcelona, Catalonia, Spain
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Kung SH, Almeida RPP. Natural competence and recombination in the plant pathogen Xylella fastidiosa. Appl Environ Microbiol 2011; 77:5278-84. [PMID: 21666009 PMCID: PMC3147478 DOI: 10.1128/aem.00730-11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 06/04/2011] [Indexed: 11/20/2022] Open
Abstract
Homologous recombination is one of many forces contributing to the diversity, adaptation, and emergence of pathogens. For naturally competent bacteria, transformation is one possible route for the acquisition of novel genetic material. This study demonstrates that Xylella fastidiosa, a generalist bacterial plant pathogen responsible for many emerging plant diseases, is naturally competent and able to homologously recombine exogenous DNA into its genome. Several factors that affect transformation and recombination efficiencies, such as nutrient availability, growth stage, and methylation of transforming DNA, were identified. Recombination was observed in at least one out of every 10(6) cells when exogenous plasmid DNA was supplied and one out of every 10(7) cells when different strains were grown together in vitro. Based on previous genomic studies and experimental data presented here, there is mounting evidence that recombination can occur at relatively high rates and could play a large role in shaping the genetic diversity of X. fastidiosa.
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Affiliation(s)
| | - Rodrigo P. P. Almeida
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California
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Coupat-Goutaland B, Bernillon D, Guidot A, Prior P, Nesme X, Bertolla F. Ralstonia solanacearum virulence increased following large interstrain gene transfers by natural transformation. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:497-505. [PMID: 21190441 DOI: 10.1094/mpmi-09-10-0197] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Horizontal gene transfer (HGT) is a major driving force of evolution and is also likely to play an important role in the threatening emergence of novel pathogens, especially if it involves distantly related strains with substantially different pathogenicity. In this study, the impact of natural transformation on pathogenicity in six strains belonging to the four phylotypes of the plant-pathogenic bacterium Ralstonia solanacearum was investigated. The study focused on genomic regions that vary between donor and recipient strains and that carry genes involved in pathogenicity such as type III effectors. First, strains from R. solanacearum species complex were naturally transformed with heterologous genomic DNA. Transferred DNA regions were then determined by comparative genomic hybridization and polymerase chain reaction sequencing. We identified three transformant strains that acquired large DNA regions of up to 80 kb. In one case, strain Psi07 (phylotype IV tomato isolate) acquired 39.4 kb from GMI1000 (phylotype I tomato isolate). Investigations revealed that i) 24.4 kb of the acquired region contained 20 new genes, ii) an allelic exchange of 12 genes occurred, and iii) 27 genes (33.4 kb) formerly present in Psi07 were lost. Virulence tests with the three transformants revealed a significant increase in the aggressiveness of BCG20 over its Psi07 parent on tomato. These findings demonstrate the potential importance of HGT in the pathogenic evolution of R. solanacearum strains and open new avenues for studying pathogen emergence.
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Affiliation(s)
- Bénédicte Coupat-Goutaland
- Université de Lyon, Université Lyon 1, CNRS, INRA, 16 rue Raphaël Dubois, Domaine Scientifique de La Doua, 69622 Villeurbanne cedex, France
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Wackler B, Schneider P, Jacobs J, Pauly J, Allen C, Nett M, Hoffmeister D. Ralfuranone Biosynthesis in Ralstonia solanacearum Suggests Functional Divergence in the Quinone Synthetase Family of Enzymes. ACTA ACUST UNITED AC 2011; 18:354-60. [DOI: 10.1016/j.chembiol.2011.01.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 12/31/2010] [Accepted: 01/07/2011] [Indexed: 11/16/2022]
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Colburn-Clifford JM, Scherf JM, Allen C. Ralstonia solanacearum Dps contributes to oxidative stress tolerance and to colonization of and virulence on tomato plants. Appl Environ Microbiol 2010; 76:7392-9. [PMID: 20870795 PMCID: PMC2976212 DOI: 10.1128/aem.01742-10] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 09/14/2010] [Indexed: 02/06/2023] Open
Abstract
Ralstonia solanacearum, an economically important soilborne plant pathogen, infects host roots to cause bacterial wilt disease. However, little is known about this pathogen's behavior in the rhizosphere and early in pathogenesis. In response to root exudates from tomato, R. solanacearum strain UW551 upregulated a gene resembling Dps, a nonspecific DNA binding protein from starved cells that is critical for stress survival in other bacteria. An R. solanacearum dps mutant had increased hydrogen peroxide sensitivity and mutation rate under starvation. Furthermore, dps expression was positively regulated by the oxidative stress response regulator OxyR. These functional results are consistent with a Dps annotation. The dps mutant caused slightly delayed bacterial wilt disease in tomato after a naturalistic soil soak inoculation. However, the dps mutant had a more pronounced reduction in virulence when bacteria were inoculated directly into host stems, suggesting that Dps helps R. solanacearum adapt to conditions inside plants. Passage through a tomato plant conferred transient increased hydrogen peroxide tolerance on both wild-type and dps mutant strains, demonstrating that R. solanacearum acquires Dps-independent oxidative stress tolerance during adaptation to the host environment. The dps mutant strain was also reduced in adhesion to tomato roots and tomato stem colonization. These results indicate that Dps is important when cells are starved or in stationary phase and that Dps contributes quantitatively to host plant colonization and bacterial wilt virulence. They further suggest that R. solanacearum must overcome oxidative stress during the bacterial wilt disease cycle.
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Affiliation(s)
| | - Jacob M. Scherf
- University of Wisconsin—Madison Department of Plant Pathology, 1630 Linden Drive, Madison, Wisconsin 53706
| | - Caitilyn Allen
- University of Wisconsin—Madison Department of Plant Pathology, 1630 Linden Drive, Madison, Wisconsin 53706
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Schneider P, Jacobs JM, Neres J, Aldrich CC, Allen C, Nett M, Hoffmeister D. The Global Virulence Regulators VsrAD and PhcA Control Secondary Metabolism in the Plant PathogenRalstonia solanacearum. Chembiochem 2009; 10:2730-2. [DOI: 10.1002/cbic.200900510] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mercier A, Bertolla F, Passelègue-Robe E, Simonet P. Influence of DNA conformation and role of comA and recA on natural transformation in Ralstonia solanacearum. Can J Microbiol 2009; 55:762-70. [PMID: 19767847 DOI: 10.1139/w09-025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Naturally competent bacteria such as the plant pathogen Ralstonia solanacearum are characterized by their ability to take up free DNA from their surroundings. In this study, we investigated the efficiency of various DNA types including chromosomal linear DNA and circular or linearized integrative and (or) replicative plasmids to naturally transform R. solanacearum. To study the respective regulatory role of DNA transport and maintenance in the definite acquisition of new DNA by bacteria, the natural transformation frequencies were compared with those obtained when the bacterial strain was transformed by electroporation. An additional round of electrotransformation and natural transformation was carried out with the same set of donor DNAs and with R. solanacearum disrupted mutants that were potentially affected in competence (comA gene) and recombination (recA gene) functions. Our results confirmed the critical role of the comA gene for natural transformation and that of recA for recombination and, more surprisingly, for the maintenance of an autonomous plasmid in the host cell. Finally, our results showed that homologous recombination of chromosomal linear DNA fragments taken up by natural transformation was the most efficient way for R. solanacearum to acquire new DNA, in agreement with previous data showing competence development and natural transformation between R. solanacearum cells in plant tissues.
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Guidot A, Coupat B, Fall S, Prior P, Bertolla F. Horizontal gene transfer between Ralstonia solanacearum strains detected by comparative genomic hybridization on microarrays. ISME JOURNAL 2009; 3:549-62. [PMID: 19242532 DOI: 10.1038/ismej.2009.14] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The plant pathogenic Betaproteobacterium Ralstonia solanacearum is a complex species in that most of the strains share the common characteristic of being naturally transformable. In this study, we used a new approach based on comparative genomic hybridization (CGH) on microarrays to investigate the extent of horizontal gene transfers (HGTs) between different strains of R. solanacearum. Recipient strains from phylotypes I, II and III were naturally transformed in vitro by genomic DNA from the GMI1000 reference strain (phylotype I) and the resulting DNAs were hybridized on a microarray representative of the 5120 predicted genes from the GMI1000 strain. In addition to transfer of the antibiotic resistance marker, in 8 of the 16 tested transformants, CGH on microarrays detected other transferred GMI1000 genes and revealed their number, category, function and localization along the genome. We showed that DNA blocks up to 30 kb and 33 genes could be integrated during a single event. Most of these blocks flanked the marker gene DNA but, interestingly, multiple DNA acquisitions along the genome also occurred in a single recombinant clone in one transformation experiment. The results were confirmed by PCR amplification, cloning and sequencing and Southern blot hybridization. This represents the first comprehensive identification of gene acquisitions and losses along the genome of the recipient bacterial strain during natural transformation experiments. In future studies, this strategy should help to answer many questions related to HGT mechanisms.
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Affiliation(s)
- Alice Guidot
- CIRAD, UMR Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Saint Pierre, La Réunion, France
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Levy-Booth DJ, Gulden RH, Campbell RG, Powell JR, Klironomos JN, Pauls KP, Swanton CJ, Trevors JT, Dunfield KE. Roundup Ready soybean gene concentrations in field soil aggregate size classes. FEMS Microbiol Lett 2009; 291:175-9. [PMID: 19076230 DOI: 10.1111/j.1574-6968.2008.01449.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Roundup Ready (RR) soybeans containing recombinant Agrobacterium spp. CP4 5-enol-pyruvyl-shikimate-3-phosphate synthase (cp4 epsps) genes tolerant to the herbicide glyphosate are extensively grown worldwide. The concentration of recombinant DNA from RR soybeans in soil aggregates was studied due to the possibility of genetic transformation of soil bacteria. This study used real-time PCR to examine the concentration of cp4 epsps in four field soil aggregate size classes (>2000 microm, 2000-500 microm, 500-250 microm and <250 microm). Aggregates over 2000 microm in diameter had significantly greater gene concentrations than those with diameters under 2000 microm. The >2000 mum fraction contained between 66.62% and 99.18% of total gene copies, although it only accounted for about 30.00% of the sampled soil. Aggregate formation may facilitate persistence of recombinant DNA.
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Affiliation(s)
- David J Levy-Booth
- Department of Environmental Biology, University of Guelph, Guelph, ON, Canada
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Coupat BÃ, Chaumeille-Dole F, Fall S, Prior P, Simonet P, Nesme X, Bertolla F. Natural transformation in the Ralstonia solanacearum species complex: number and size of DNA that can be transferred. FEMS Microbiol Ecol 2008; 66:14-24. [DOI: 10.1111/j.1574-6941.2008.00552.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Targeted mutagenesis of Burkholderia thailandensis and Burkholderia pseudomallei through natural transformation of PCR fragments. Appl Environ Microbiol 2008; 74:2985-9. [PMID: 18310423 DOI: 10.1128/aem.00030-08] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Burkholderia pseudomallei is the causative agent of melioidosis, an overwhelming, rapidly fatal septic infection, and B. thailandensis is a closely related, less virulent species. Both organisms are naturally competent for DNA transformation, and this report describes a procedure exploiting this property for the rapid generation of marked deletion mutations by using PCR products. The method was employed to create 61 mutant strains. Several selectable elements were employed, including elements carrying loxP and FRT recombinase recognition sites to facilitate resistance marker excision. Chromosomal mutations could also be transferred readily between strains by transformation. The availability of simple procedures for creating defined chromosomal mutations and moving them between strains should facilitate genetic analysis of virulence and other traits of these two Burkholderia species.
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Pontiroli A, Simonet P, Frostegard A, Vogel TM, Monier JM. Fate of transgenic plant DNA in the environment. ACTA ACUST UNITED AC 2007; 6:15-35. [DOI: 10.1051/ebr:2007037] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Fall S, Mercier A, Bertolla F, Calteau A, Gueguen L, Perrière G, Vogel TM, Simonet P. Horizontal gene transfer regulation in bacteria as a "spandrel" of DNA repair mechanisms. PLoS One 2007; 2:e1055. [PMID: 17957239 PMCID: PMC2013936 DOI: 10.1371/journal.pone.0001055] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 10/02/2007] [Indexed: 12/01/2022] Open
Abstract
Horizontal gene transfer (HGT) is recognized as the major force for bacterial genome evolution. Yet, numerous questions remain about the transferred genes, their function, quantity and frequency. The extent to which genetic transformation by exogenous DNA has occurred over evolutionary time was initially addressed by an in silico approach using the complete genome sequence of the Ralstonia solanacearum GMI1000 strain. Methods based on phylogenetic reconstruction of prokaryote homologous genes families detected 151 genes (13.3%) of foreign origin in the R. solanacearum genome and tentatively identified their bacterial origin. These putative transfers were analyzed in comparison to experimental transformation tests involving 18 different genomic DNA positions in the genome as sites for homologous or homeologous recombination. Significant transformation frequency differences were observed among these positions tested regardless of the overall genomic divergence of the R. solanacearum strains tested as recipients. The genomic positions containing the putative exogenous DNA were not systematically transformed at the highest frequencies. The two genomic “hot spots”, which contain recA and mutS genes, exhibited transformation frequencies from 2 to more than 4 orders of magnitude higher than positions associated with other genes depending on the recipient strain. These results support the notion that the bacterial cell is equipped with active mechanisms to modulate acquisition of new DNA in different genomic positions. Bio-informatics study correlated recombination “hot-spots” to the presence of Chi-like signature sequences with which recombination might be preferentially initiated. The fundamental role of HGT is certainly not limited to the critical impact that the very rare foreign genes acquired mainly by chance can have on the bacterial adaptation potential. The frequency to which HGT with homologous and homeologous DNA happens in the environment might have led the bacteria to hijack DNA repair mechanisms in order to generate genetic diversity without losing too much genomic stability.
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Affiliation(s)
- Saliou Fall
- Environmental Microbial Genomics Group, Laboratoire AMPERE UMR CNRS 5005, Ecole Centrale de Lyon et Université de Lyon, Ecully, France
| | - Anne Mercier
- Ecologie Microbienne, UMR CNRS 5557, Université Claude Bernard–Lyon 1, Villeurbanne, France
| | - Franck Bertolla
- Ecologie Microbienne, UMR CNRS 5557, Université Claude Bernard–Lyon 1, Villeurbanne, France
| | - Alexandra Calteau
- Laboratoire de Biométrie et Biologie Évolutive, UMR CNRS 5558, Université Claude Bernard–Lyon 1, Villeurbanne, France
| | - Laurent Gueguen
- Laboratoire de Biométrie et Biologie Évolutive, UMR CNRS 5558, Université Claude Bernard–Lyon 1, Villeurbanne, France
| | - Guy Perrière
- Laboratoire de Biométrie et Biologie Évolutive, UMR CNRS 5558, Université Claude Bernard–Lyon 1, Villeurbanne, France
| | - Timothy M. Vogel
- Environmental Microbial Genomics Group, Laboratoire AMPERE UMR CNRS 5005, Ecole Centrale de Lyon et Université de Lyon, Ecully, France
| | - Pascal Simonet
- Environmental Microbial Genomics Group, Laboratoire AMPERE UMR CNRS 5005, Ecole Centrale de Lyon et Université de Lyon, Ecully, France
- * To whom correspondence should be addressed. E-mail:
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Johnsborg O, Eldholm V, Håvarstein LS. Natural genetic transformation: prevalence, mechanisms and function. Res Microbiol 2007; 158:767-78. [PMID: 17997281 DOI: 10.1016/j.resmic.2007.09.004] [Citation(s) in RCA: 229] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Revised: 09/04/2007] [Accepted: 09/21/2007] [Indexed: 02/02/2023]
Abstract
Studies show that gene acquisition through natural transformation has contributed significantly to the adaptation and ecological diversification of several bacterial species. Relatively little is still known, however, about the prevalence and phylogenetic distribution of organisms possessing this property. Thus, whether natural transformation only benefits a limited number of species or has a large impact on lateral gene flow in nature remains a matter of speculation. Here we will review the most recent advances in our understanding of the phenomenon and discuss its possible biological functions.
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Affiliation(s)
- Ola Johnsborg
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, As, Norway
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Simpson DJ, Dawson LF, Fry JC, Rogers HJ, Day MJ. Influence of flanking homology and insert size on the transformation frequency ofAcinetobacter baylyiBD413. ACTA ACUST UNITED AC 2007; 6:55-69. [DOI: 10.1051/ebr:2007027] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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47
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Mercier A, Bertolla F, Passelègue-Robe E, Simonet P. Natural transformation-based foreign DNA acquisition in a Ralstonia solanacearum mutS mutant. Res Microbiol 2007; 158:537-44. [PMID: 17618086 DOI: 10.1016/j.resmic.2007.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Accepted: 05/11/2007] [Indexed: 11/29/2022]
Abstract
Mutator strains with defective methyl-mismatch repair (MMR) systems have been shown to play an important role in adaptation of bacterial populations to changing and stressful environments. In this report, we describe the impact of mutS::aacC3-IV inactivation on foreign DNA acquisition by natural transformation in the phytopathogenic bacterium Ralstonia solanacearum. A mutS mutant of R. solanacearum exhibited 33- to 60-fold greater spontaneous mutation frequencies, in accordance with a mutator phenotype. Transformation experiments indicated that intra- and interspecific DNA transfers increased up to 89-fold. To assess horizontal gene transfer (HGT) from genetically modified plants to R. solanacearum, fitness of the mutator was first evaluated in soil and plant environments. Competitiveness was not modified after 61 days in soil and 8 days in tomato, and the progress of plant decay symptoms was similar to that of the wild-type strain. Despite its survival in soil and in planta, and the powerful capacities of HGT, R. solanacearum was not genetically transformed by transgenic plant DNA in a wide range of in vitro and in planta tests.
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Monier JM, Bernillon D, Kay E, Faugier A, Rybalka O, Dessaux Y, Simonet P, Vogel TM. Detection of potential transgenic plant DNA recipients among soil bacteria. ENVIRONMENTAL BIOSAFETY RESEARCH 2007; 6:71-83. [PMID: 17961481 DOI: 10.1051/ebr:2007036] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The likelihood of gene transfer from transgenic plants to bacteria is dependent on gene number and the presence of homologous sequences. The large number of transgene copies in transplastomic (transgenes contained in the chloroplast genome) plant cells as well as the prokaryotic origin of the transgene, may thus significantly increase the likelihood of gene transfer to bacteria that colonize plant tissues. In order to assess the probability of such transfer, the length of homologous DNA sequences required between the transgene and the genome of the bacterial host was assessed. In addition, the probability that bacteria, which co-infect diseased plants, are transformable and have sequences similar to the flanking regions of the transgene was evaluated. Using Acinetobacter baylyi strain BD143 and transplastomic tobacco plants harboring the aadA gene (streptomycin and spectinomycin resistance), we found that sequences identical to the flanking regions containing as few as 55 nucleotides were sufficient for recombination to occur. Consequently, a collection of bacterial isolates able to colonize tobacco plant tissue infected by Ralstonia solanacearum strain K60 was obtained, screened for DNA sequence similarity with the chloroplastic genes accD and rbcL flanking the transgene, and tested for their ability to uptake extracellular DNA (broad host-range pBBR1MCS plasmids) by natural or electro-transformation. Results showed that among the 288 bacterial isolates tested, 8% presented DNA sequence similarity with one or both chloroplastic regions flanking the transgene. Two isolates, identified as Pseudomonas sp. and Acinetobacter sp., were able to integrate exogenous plasmid DNA by electro-transformation and natural transformation, respectively. Our data suggest that transplastomic plant DNA recipients might be present in soil bacterial communities.
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Affiliation(s)
- Jean-Michel Monier
- Ecologie Microbienne, Université de Lyon, 69003 Lyon, Lyon I, 69622, Villeurbanne, France.
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Grover A, Azmi W, Gadewar AV, Pattanayak D, Naik PS, Shekhawat GS, Chakrabarti SK. Genotypic diversity in a localized population of Ralstonia solanacearum as revealed by random amplified polymorphic DNA markers. J Appl Microbiol 2006; 101:798-806. [PMID: 16968291 DOI: 10.1111/j.1365-2672.2006.02974.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To assess genotypic diversity within Ralstonia solanacearum isolates of a single field. METHODS AND RESULTS A total of 44 field isolates and 22 in vitro generated clones of R. solanacearum were studied for genotypic diversity by random amplified polymorphic DNA (RAPD) technique. Genomic DNA of these isolates and clones was extracted by proteinase-K-SDS lysis mini-prep method. RAPD analysis was done with 30 decamer primers. The data were analysed using NTSYSpc 2.02h software. Forty-two out of 44 field isolates and all the clonal isolates were identified as distinct genotypes at 70% similarity level. CONCLUSION Very high level of genome variability was observed within the field and clonal isolates of R. solanacearum. This might be a reason for the wide host range of this bacterium and for quick breakdown of wilt resistance in host plants. SIGNIFICANCE AND IMPACT OF THE STUDY The results suggest that it would be difficult to design specific diagnostic protocol for R. solanacearum even for a localized population and to breed cultivars with broad-spectrum resistance.
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Affiliation(s)
- A Grover
- Central Potato Research Institute, Shimla, Himachal Pradesh, India
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Liu H, Zhang S, Schell MA, Denny TP. Pyramiding unmarked deletions in Ralstonia solanacearum shows that secreted proteins in addition to plant cell-wall-degrading enzymes contribute to virulence. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:1296-305. [PMID: 16478049 DOI: 10.1094/mpmi-18-1296] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Ralstonia solanacearum, like many phytopathogenic bacteria, makes multiple extracellular plant cell-wall-degrading enzymes (CWDE), some of which contribute to its ability to cause wilt disease. CWDE and many other proteins are secreted to the milieu via the highly conserved type II protein secretion system (T2SS). R. solanacearum with a defective T2SS is weakly virulent, but it is not known whether this is due to absence of all the CWDE or the loss of other secreted proteins that contribute to disease. These alternatives were investigated by creating mutants of wild-type strain GMI1000 lacking either the T2SS or up to six CWDE and comparing them for virulence on tomato plants. To create unmarked deletions, genomic regions flanking the target gene were polymerase chain reaction (PCR)-amplified, were fused using splice overlap extension PCR, were cloned into a suicide plasmid harboring the sacB counter-selectable marker, and then, were site-specifically introduced into the genome. Various combinations of five deletions (delta pehA, delta pehB, delta B, PehC, and Pme) was not statistically different from GMI1000, but all the mutants lacking one or both cellulolytic enzymes (Egl or CbhA) wilted plants significantly more slowly than did the wild type. The GMI-6 mutant that lacks all six CWDE was more virulent than the mutant lacking only its two cellulolytic enzymes, and both were significantly more virulent than the T2SS mutant (GMI-D). Very similar results were observed in wounded-petiole inoculation assays, so GMI-6 and GMI-D appear to be less capable of colonizing tomato tissues after invasion. Because the T2SS mutant was much less virulent than the sixfold CWDE mutant, we conclude that other secreted proteins contribute substantially to the ability of R. solanacearum GMI1000 to systemically colonize tomato plants.
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Affiliation(s)
- Huanli Liu
- Department of Plant Pathology, The University of Georgia, Athens, Georgia 30602, USA
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