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Zhang H, Xu Y, Huang Y, Xiong X, Wu X, Yuan G, Zheng D. Tn-seq identifies Ralstonia solanacearum genes required for tolerance of plant immunity induced by exogenous salicylic acid. MOLECULAR PLANT PATHOLOGY 2023; 24:536-548. [PMID: 36912695 DOI: 10.1111/mpp.13321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/20/2023] [Accepted: 02/20/2023] [Indexed: 05/18/2023]
Abstract
Ralstonia solanacearum, the causal agent of the devastating bacterial wilt disease, is of particular interest to the scientific community. The repertoire of type III effectors plays an important role in the evasion of plant immunity, but tolerance to plant immunity is also crucial for the survival and virulence of R. solanacearum. Nevertheless, a systematic study of R. solanacearum tolerance to plant immunity is lacking. In this study, we used exogenous salicylic acid (SA) to improve the immunity of tomato plants, followed by transposon insertion sequencing (Tn-seq) analysis and the identification of R. solanacearum genes associated with tolerance to plant immunity. Target gene deletion revealed that the lipopolysaccharide (LPS) production genes RS_RS02830, RS_RS03460, and RS_RS03465 are essential for R. solanacearum tolerance to plant immunity, and their expression is induced by plant immunity, thereby expanding our knowledge of the pathogenic function of R. solanacearum LPS. SA treatment increased the relative abundance of transposon insertion mutants of four genes, including two genes with unknown function, RS_RS11975 and RS_RS07760. Further verification revealed that deletion of RS_RS11975 or RS_RS07760 resulted in reduced in vivo competitive indexes but increased tolerance to plant immunity induced by SA treatment, suggesting that these two genes contribute to the trade-off between tolerance to plant immunity and fitness cost. In conclusion, this work identified and validated R. solanacearum genes required for tolerance to plant immunity and provided essential information for a more complete view of the interaction between R. solanacearum and the host plant.
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Affiliation(s)
- Huimeng Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
| | - Yanan Xu
- Pharmaceutical College, Guangxi Medical University, Nanning, China
| | - Yingying Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
| | - Xiaoqi Xiong
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
| | - Xiaogang Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
| | - Gaoqing Yuan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
| | - Dehong Zheng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-environment and Agro-product Safety, College of Agriculture, Guangxi University, Nanning, China
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Xie T, Wu X, Luo L, Qu Y, Fan R, Wu S, Long Y, Zhao Z. Natural variation in the hrpL promoter renders the phytopathogen Pseudomonas syringae pv. actinidiae nonpathogenic. MOLECULAR PLANT PATHOLOGY 2023; 24:262-271. [PMID: 36600466 PMCID: PMC9923390 DOI: 10.1111/mpp.13289] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/22/2022] [Accepted: 12/09/2022] [Indexed: 05/14/2023]
Abstract
The genetic basis underlying loss-of-virulence mutations that arise among natural phytopathogen populations is not well documented. In this study, we examined the virulence of 377 isolates of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) that were isolated from 76 kiwifruit orchards suffering from bacterial canker disease. Eighty-four nonpathogenic isolates were identified in 40 orchards. A nonpathogenic isolate G166 was found to be defective in hrpL transcription and the downstream type III secretion system (T3SS)-dependent phenotypes. Comparative genomics and complementary expression assay revealed that a single-base "G" insertion in the hrpL promoter blocks gene transcription by reducing promoter activity. The electrophoretic mobility shift assay showed that the genetic variation impairs σ54 /promoter binding during gene transcription under hrp-inducing conditions, resulting in lower expression of hrpL. A PCR-restriction fragment length polymorphism assay was performed to trace the evolutionary history of this mutation, which revealed the independent onset of genetic variations in natural Psa3 populations. We also found that nonpathogenic variants outperformed virulent Psa3 bacteria for both epiphytic and apoplast colonization of kiwifruit leaves in mixed inoculations. Our study highlights a novel mechanism for loss of virulence in Psa3 and provides insight into bacterial adaptive evolution under natural settings.
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Affiliation(s)
- Ting Xie
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Xiujiao Wu
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Le Luo
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Yuan Qu
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Rong Fan
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
| | - Shiping Wu
- Institute of Plant ProtectionGuizhou Academy of Agricultural SciencesGuiyangChina
| | - Youhua Long
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
| | - Zhibo Zhao
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
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Cooperative virulence via the collective action of secreted pathogen effectors. Nat Microbiol 2023; 8:640-650. [PMID: 36782026 DOI: 10.1038/s41564-023-01328-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 01/13/2023] [Indexed: 02/15/2023]
Abstract
Although virulence is typically attributed to single pathogenic strains, here we investigated whether effectors secreted by a population of non-virulent strains could function as public goods to enable the emergence of collective virulence. We disaggregated the 36 type III effectors of the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 into a 'metaclone' of 36 coisogenic strains, each carrying a single effector in an effectorless background. Each coisogenic strain was individually unfit, but the metaclone was collectively as virulent as the wild-type strain on Arabidopsis thaliana, suggesting that effectors can drive the emergence of cooperation-based virulence through their public action. We show that independently evolved effector suits can equally drive this cooperative behaviour by transferring the effector alleles native to the strain PmaES4326 into the conspecific but divergent strain PtoDC3000. Finally, we transferred the disaggregated PtoDC3000 effector arsenal into Pseudomonas fluorescens and show that their cooperative action was sufficient to convert this rhizosphere-inhabiting beneficial bacterium into a phyllosphere pathogen. These results emphasize the importance of microbial community interactions and expand the ecological scale at which disease may be attributed.
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Antimicrobial and Antiviral Compounds of Phlomis viscosa Poiret. Biomedicines 2023; 11:biomedicines11020441. [PMID: 36830977 PMCID: PMC9953047 DOI: 10.3390/biomedicines11020441] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/26/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
Phlomis viscosa Poiret (an evergreen shrub) represents a valuable source of medicinal compounds. In this study, we discovered compounds with antimicrobial and antiviral properties. The aim of this study was to identify compounds of P. viscosa and estimate the antimicrobial and antiviral activity of its phytochemicals. The volatile compounds were identified using gas chromatography/mass spectrometry (GC/MS) analysis. For the identification of nonvolatile components of the extracts, high-performance liquid chromatography (HPLC), liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) were applied. Quercetin 3-O-rutinoside and hesperidin caused a significant decrease in the bacterial concentration of Agrobacterium tumefaciens, Xylella fastidiosa and Pseudomonas syringae (p < 0.001). The growth of drug-resistant microorganisms (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Serratia marcescens and Salmonella enteritidis) was inhibited by quercetin 3-O-rutinoside, quercetin 3-O-arabinoside and hesperidin. In addition, these compounds demonstrated antiquorum-sensing properties. Diosmin, hesperidin and quercetin 3-O-arabinoside significantly inhibited varicella zoster virus (VZV) (p < 0.001). Quercetin 3-O-rutinoside and quercetin 3-O-arabinoside were effective against herpes simplex virus 1 (HSV-1), including mutant strains.
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Hulin MT, Rabiey M, Zeng Z, Vadillo Dieguez A, Bellamy S, Swift P, Mansfield JW, Jackson RW, Harrison RJ. Genomic and functional analysis of phage-mediated horizontal gene transfer in Pseudomonas syringae on the plant surface. THE NEW PHYTOLOGIST 2023; 237:959-973. [PMID: 36285389 PMCID: PMC10107160 DOI: 10.1111/nph.18573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Many strains of Pseudomonas colonise plant surfaces, including the cherry canker pathogens, Pseudomonas syringae pathovars syringae and morsprunorum. We have examined the genomic diversity of P. syringae in the cherry phyllosphere and focused on the role of prophages in transfer of genes encoding Type 3 secreted effector (T3SE) proteins contributing to the evolution of virulence. Phylogenomic analysis was carried out on epiphytic pseudomonads in the UK orchards. Significant differences in epiphytic populations occurred between regions. Nonpathogenic strains were found to contain reservoirs of T3SE genes. Members of P. syringae phylogroups 4 and 10 were identified for the first time from Prunus. Using bioinformatics, we explored the presence of the gene encoding T3SE HopAR1 within related prophage sequences in diverse P. syringae strains including cherry epiphytes and pathogens. Results indicated that horizontal gene transfer (HGT) of this effector between phylogroups may have involved phage. Prophages containing hopAR1 were demonstrated to excise, circularise and transfer the gene on the leaf surface. The phyllosphere provides a dynamic environment for prophage-mediated gene exchange and the potential for the emergence of new more virulent pathotypes. Our results suggest that genome-based epidemiological surveillance of environmental populations will allow the timely application of control measures to prevent damaging diseases.
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Affiliation(s)
- Michelle T. Hulin
- NIABLawrence Weaver RoadCambridgeCB3 0LEUK
- The Sainsbury LaboratoryNorwichNR4 7UHUK
| | - Mojgan Rabiey
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamB15 2TTUK
| | - Ziyue Zeng
- NIABLawrence Weaver RoadCambridgeCB3 0LEUK
| | | | | | - Phoebe Swift
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamB15 2TTUK
| | | | - Robert W. Jackson
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamB15 2TTUK
| | - Richard J. Harrison
- NIABLawrence Weaver RoadCambridgeCB3 0LEUK
- Present address:
Plant Science GroupWageningen University and ResearchWageningen6708WBthe Netherlands
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Luneau JS, Baudin M, Quiroz Monnens T, Carrère S, Bouchez O, Jardinaud M, Gris C, François J, Ray J, Torralba B, Arlat M, Lewis JD, Lauber E, Deutschbauer AM, Noël LD, Boulanger A. Genome-wide identification of fitness determinants in the Xanthomonas campestris bacterial pathogen during early stages of plant infection. THE NEW PHYTOLOGIST 2022; 236:235-248. [PMID: 35706385 PMCID: PMC9543026 DOI: 10.1111/nph.18313] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 06/07/2022] [Indexed: 05/31/2023]
Abstract
Plant diseases are an important threat to food production. While major pathogenicity determinants required for disease have been extensively studied, less is known on how pathogens thrive during host colonization, especially at early infection stages. Here, we used randomly barcoded-transposon insertion site sequencing (RB-TnSeq) to perform a genome-wide screen and identify key bacterial fitness determinants of the vascular pathogen Xanthomonas campestris pv campestris (Xcc) during infection of the cauliflower host plant (Brassica oleracea). This high-throughput analysis was conducted in hydathodes, the natural entry site of Xcc, in xylem sap and in synthetic media. Xcc did not face a strong bottleneck during hydathode infection. In total, 181 genes important for fitness were identified in plant-associated environments with functional enrichment in genes involved in metabolism but only few genes previously known to be involved in virulence. The biological relevance of 12 genes was independently confirmed by phenotyping single mutants. Notably, we show that XC_3388, a protein with no known function (DUF1631), plays a key role in the adaptation and virulence of Xcc possibly through c-di-GMP-mediated regulation. This study revealed yet unsuspected social behaviors adopted by Xcc individuals when confined inside hydathodes at early infection stages.
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Affiliation(s)
- Julien S. Luneau
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Maël Baudin
- Plant Gene Expression Center, USDAAlbanyCA94710USA
- Department of Plant and Microbial BiologyUniversity of CaliforniaBerkeleyCA94720USA
| | - Thomas Quiroz Monnens
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Sébastien Carrère
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Olivier Bouchez
- Genotoul Genome & Transcriptome (GeT‐PlaGe), INRAE31320Castanet‐TolosanFrance
| | | | - Carine Gris
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Jonas François
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Jayashree Ray
- Environmental Genomics and Systems Biology DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
| | - Babil Torralba
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Matthieu Arlat
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Jennifer D. Lewis
- Plant Gene Expression Center, USDAAlbanyCA94710USA
- Department of Plant and Microbial BiologyUniversity of CaliforniaBerkeleyCA94720USA
| | - Emmanuelle Lauber
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Adam M. Deutschbauer
- Department of Plant and Microbial BiologyUniversity of CaliforniaBerkeleyCA94720USA
- Environmental Genomics and Systems Biology DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
| | - Laurent D. Noël
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
| | - Alice Boulanger
- LIPME, Université de Toulouse, INRAE, CNRSUniversité Paul Sabatier31320Castanet‐TolosanFrance
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7
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Xing B, Zheng Y, Zhang M, Liu X, Li L, Mou C, Wu Q, Guo H, Shao Q. Biocontrol: Endophytic bacteria could be crucial to fight soft rot disease in the rare medicinal herb, Anoectochilus roxburghii. Microb Biotechnol 2022; 15:2929-2941. [PMID: 36099393 PMCID: PMC9733646 DOI: 10.1111/1751-7915.14142] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/21/2022] [Accepted: 08/26/2022] [Indexed: 12/14/2022] Open
Abstract
Microbial destabilization induced by pathogen infection has severely affected plant quality and output, such as Anoectochilus roxburghii, an economically important herb. Soft rot is the main disease that occurs during A. roxburghii culturing. However, the key members of pathogens and their interplay with non-detrimental microorganisms in diseased plants remain largely unsolved. Here, by utilizing a molecular ecological network approach, the interactions within bacterial communities in endophytic compartments and the surrounding soils during soft rot infection were investigated. Significant differences in bacterial diversity and community composition between healthy and diseased plants were observed, indicating that the endophytic communities were strongly influenced by pathogen invasion. Endophytic stem communities of the diseased plants were primarily derived from roots and the root endophytes were largely derived from rhizosphere soils, which depicts a possible pathogen migration image from soils to roots and finally the stems. Furthermore, interactions among microbial members indicated that pathogen invasion might be aided by positively correlated native microbial members, such as Enterobacter and Microbacterium, who may assist in colonization and multiplication through a mutualistic relationship in roots during the pathogen infection process. Our findings will help open new avenues for developing more accurate strategies for biological control of A. roxburghii bacterial soft rot disease.
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Affiliation(s)
- Bingcong Xing
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Ying Zheng
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Man Zhang
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Xinting Liu
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Lihong Li
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Chenhao Mou
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Qichao Wu
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
| | - Haipeng Guo
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐Products, School of Marine SciencesNingbo UniversityNingboChina
| | - Qingsong Shao
- State Key Laboratory of Subtropical SilvicultureZhejiang A&F UniversityHangzhouChina,Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese MedicineZhejiang A&F UniversityHangzhouChina
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Gurney J, Simonet C, Wollein Waldetoft K, Brown SP. Challenges and opportunities for cheat therapy in the control of bacterial infections. Nat Prod Rep 2021; 39:325-334. [PMID: 34913456 DOI: 10.1039/d1np00053e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Covering: 1999 to 2021Bacterial pathogens can be highly social, communicating and cooperating within multi-cellular groups to make us sick. The requirement for collective action in pathogens presents novel therapeutic avenues that seek to undermine cooperative behavior, what we call here 'cheat therapies'. We review two broad avenues of cheat therapy: first, the introduction of genetically engineered 'cheat' strains (bio-control cheats), and second the chemical induction of 'cheat' behavior in the infecting pathogens (chemical-control cheats). Both genetically engineered and chemically induced cheats can socially exploit the cooperative wildtype infection, reducing pathogen burden and the severity of disease. We review the costs and benefits of cheat therapies, highlighting advantages of evolutionary robustness and also the challenges of low to moderate efficacy, compared to conventional antibiotic treatments. We end with a summary of what we see as the most valuable next steps, focusing on adjuvant treatments and use as alternate therapies for mild, self-resolving infections - allowing the reservation of current and highly effective antibiotics for more critical patient needs.
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Affiliation(s)
- James Gurney
- Center for Microbial Dynamics & Infection, Georgia Institute of Technology, Atlanta, 30332 GA, USA. .,School of Biological Sciences, Georgia Institute of Technology, Atlanta, 30332 GA, USA
| | - Camille Simonet
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Kristofer Wollein Waldetoft
- Center for Microbial Dynamics & Infection, Georgia Institute of Technology, Atlanta, 30332 GA, USA. .,School of Biological Sciences, Georgia Institute of Technology, Atlanta, 30332 GA, USA.,Torsby Hospital, Torsby, Sweden
| | - Sam P Brown
- Center for Microbial Dynamics & Infection, Georgia Institute of Technology, Atlanta, 30332 GA, USA. .,School of Biological Sciences, Georgia Institute of Technology, Atlanta, 30332 GA, USA
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9
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Su Y, Xu Y, Liang H, Yuan G, Wu X, Zheng D. Genome-Wide Identification of Ralstonia solanacearum Genes Required for Survival in Tomato Plants. mSystems 2021; 6:e0083821. [PMID: 34636662 PMCID: PMC8510521 DOI: 10.1128/msystems.00838-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 09/24/2021] [Indexed: 01/22/2023] Open
Abstract
Ralstonia solanacearum is an extremely destructive phytopathogenic bacterium for which there is no effective control method. Though many pathogenic factors have been identified, the survival strategies of R. solanacearum in host plants remain unclear. Transposon insertion sequencing (Tn-seq) is a high-throughput genetic screening technology. This study conducted a Tn-seq analysis using the in planta environment as selective pressure to identify R. solanacearum genes required for survival in tomato plants. One hundred thirty genes were identified as putative genes required for survival in tomato plants. Sixty-three of these genes were classified into four Clusters of Orthologous Groups categories. The absence of genes that encode the outer membrane lipoprotein LolB (RS_RS01965) or the membrane protein RS_RS04475 severely decreased the in planta fitness of R. solanacearum. RS_RS09970 and RS_RS04490 are involved in tryptophan and serine biosynthesis, respectively. Mutants that lack RS_RS09970 or RS_RS04490 did not cause any wilt symptoms in susceptible tomato plants. These results confirmed the importance of genes related to "cell wall/membrane/envelope biogenesis" and "amino acid transport and metabolism" for survival in plants. The gene encoding NADH-quinone oxidoreductase subunit B (RS_RS10340) is one of the 13 identified genes involved in "energy production and conversion," and the Clp protease gene (RS_RS08645) is one of the 11 identified genes assigned to "posttranslational modification, protein turnover, and chaperones." Both genes were confirmed to be required for survival in plants. In conclusion, this study globally identified and validated R. solanacearum genes required for survival in tomato plants and provided essential information for a more complete view of the pathogenic mechanism of R. solanacearum. IMPORTANCE Tomato plant xylem is a nutritionally limiting and dynamically changing habitat. Studies on how R. solanacearum survives in this hostile environment are important for our full understanding of the pathogenic mechanism of this bacterium. Though many omics approaches have been employed to study in planta survival strategies, the direct genome-wide identification of R. solanacearum genes required for survival in plants is still lacking. This study performed a Tn-seq analysis in R. solanacearum and revealed that genes in the categories "cell wall/membrane/envelope biogenesis," "amino acid transport and metabolism," "energy production and conversion," "posttranslational modification, protein turnover, chaperones" and others play important roles in the survival of R. solanacearum in tomato plants.
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Affiliation(s)
- Yaxing Su
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-Environment and Agro-Product Safety, College of Agriculture, Guangxi University, Nanning, People’s Republic of China
| | - Yanan Xu
- Pharmaceutical College, Guangxi Medical University, Nanning, People’s Republic of China
| | - Hailing Liang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-Environment and Agro-Product Safety, College of Agriculture, Guangxi University, Nanning, People’s Republic of China
| | - Gaoqing Yuan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-Environment and Agro-Product Safety, College of Agriculture, Guangxi University, Nanning, People’s Republic of China
| | - Xiaogang Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-Environment and Agro-Product Safety, College of Agriculture, Guangxi University, Nanning, People’s Republic of China
| | - Dehong Zheng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Key Laboratory of Agro-Environment and Agro-Product Safety, College of Agriculture, Guangxi University, Nanning, People’s Republic of China
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