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Chu LT, Laxman D, Abdelhamed J, Pirlo RK, Fan F, Wagner N, Tran TM, Bui L. Development of a tomato xylem-mimicking microfluidic system to study Ralstonia pseudosolanacearum biofilm formation. Front Bioeng Biotechnol 2024; 12:1395959. [PMID: 38860138 PMCID: PMC11163092 DOI: 10.3389/fbioe.2024.1395959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 04/18/2024] [Indexed: 06/12/2024] Open
Abstract
The bacterial wilt pathogen Ralstonia pseudosolanacearum (Rps) colonizes plant xylem vessels and blocks the flow of xylem sap by its biofilm (comprising of bacterial cells and extracellular material), resulting in devastating wilt disease across many economically important host plants including tomatoes. The technical challenges of imaging the xylem environment, along with the use of artificial cell culture plates and media in existing in vitro systems, limit the understanding of Rps biofilm formation and its infection dynamics. In this study, we designed and built a microfluidic system that mimicked the physical and chemical conditions of the tomato xylem vessels, and allowed us to dissect Rps responses to different xylem-like conditions. The system, incorporating functional surface coatings of carboxymethyl cellulose-dopamine, provided a bioactive environment that significantly enhanced Rps attachment and biofilm formation in the presence of tomato xylem sap. Using computational approaches, we confirmed that Rps experienced linear increasing drag forces in xylem-mimicking channels at higher flow rates. Consistently, attachment and biofilm assays conducted in our microfluidic system revealed that both seeding time and flow rates were critical for bacterial adhesion to surface and biofilm formation inside the channels. These findings provided insights into the Rps attachment and biofilm formation processes, contributing to a better understanding of plant-pathogen interactions during wilt disease development.
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Affiliation(s)
- Lan Thanh Chu
- Department of Biology, University of Dayton, Dayton, OH, United States
| | - Deeksha Laxman
- Department of Biology, University of Dayton, Dayton, OH, United States
| | - Jenna Abdelhamed
- Department of Biology, University of Dayton, Dayton, OH, United States
| | - Russell Kirk Pirlo
- Department of Chemical and Materials Engineering, University of Dayton, Dayton, OH, United States
| | - Fei Fan
- Department of Chemistry, Michigan State University, East Lansing, MI, United States
| | - Nicholas Wagner
- Department of Biology, University of South Alabama, Mobile, AL, United States
| | - Tuan Minh Tran
- Department of Biology, University of South Alabama, Mobile, AL, United States
| | - Loan Bui
- Department of Biology, University of Dayton, Dayton, OH, United States
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2
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Guo QQ, Li YZ, Shi HB, Yi AY, Xu XL, Wang HH, Deng X, Wu ZB, Cui ZN. Novel mandelic acid derivatives suppress virulence of Ralstonia solanacearum via type III secretion system. PEST MANAGEMENT SCIENCE 2023; 79:4626-4634. [PMID: 37442803 DOI: 10.1002/ps.7664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/07/2023] [Accepted: 07/14/2023] [Indexed: 07/15/2023]
Abstract
BACKGROUND Bacterial wilt induced by Ralstonia solanacearum is regarded as one of the most devastating diseases. However, excessive and repeated use of the same bactericides has resulted in development of bacterial resistance. Targeting bacterial virulence factors, such as type III secretion system (T3SS), without inhibiting bacterial growth is a possible assay to discover new antimicrobial agents. RESULTS In this work, identifying new T3SS inhibitors, a series of mandelic acid derivatives with 2-mercapto-1,3,4-thiazole moiety was synthesized. One of them, F-24, inhibited the transcription of hrpY gene significantly. The presence of this compound obviously attenuated hypersensitive response (HR) without inhibiting bacterial growth of R. solanacearum. The transcription levels of those typical T3SS genes were reduced to various degrees. The test of the ability of F-24 in protecting plants demonstrated that F-24 protected tomato plants against bacterial wilt without restricting the multiplication of R. solanacearum. The mechanism of this T3SS inhibition is through the PhcR-PhcA-PrhG-HrpB pathway. CONCULSION The screened F-24 could inhibit R. solanacearum T3SS and showed better inhibitory activity than previously reported inhibitors without affecting the growth of the strain, and F-24 is a compound with good potential in the control of R. solanacearum. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Qiao-Qiao Guo
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Yu-Zhen Li
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Hua-Bin Shi
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, China
| | - Ao-Yun Yi
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
| | - Xiao-Li Xu
- Instrumental Analysis and Research Center, South China Agricultural University, Guangzhou, China
| | - Hai-Hong Wang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Xin Deng
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon Tong, Hong Kong
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen, China
| | - Zhi-Bing Wu
- National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, China
| | - Zi-Ning Cui
- National Key Laboratory of Green Pesticide, Integrative Microbiology Research Center, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou, China
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3
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Vailleau F, Genin S. Ralstonia solanacearum: An Arsenal of Virulence Strategies and Prospects for Resistance. ANNUAL REVIEW OF PHYTOPATHOLOGY 2023; 61:25-47. [PMID: 37506349 DOI: 10.1146/annurev-phyto-021622-104551] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
The group of strains constituting the Ralstonia solanacearum species complex (RSSC) is a prominent model for the study of plant-pathogenic bacteria because of its impact on agriculture, owing to its wide host range, worldwide distribution, and long persistence in the environment. RSSC strains have led to numerous studies aimed at deciphering the molecular bases of virulence, and many biological functions and mechanisms have been described to contribute to host infection and pathogenesis. In this review, we put into perspective recent advances in our understanding of virulence in RSSC strains, both in terms of the inventory of functions that participate in this process and their evolutionary dynamics. We also present the different strategies that have been developed to combat these pathogenic strains through biological control, antimicrobial agents, plant genetics, or microbiota engineering.
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Affiliation(s)
- Fabienne Vailleau
- LIPME, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France; ,
| | - Stéphane Genin
- LIPME, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France; ,
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4
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Xia H, Huang Y, Wu R, Tang X, Cai J, Li SX, Jiang L, Wu D. A screening identifies harmine as a novel antibacterial compound against Ralstonia solanacearum. Front Microbiol 2023; 14:1269567. [PMID: 37731919 PMCID: PMC10507859 DOI: 10.3389/fmicb.2023.1269567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 08/22/2023] [Indexed: 09/22/2023] Open
Abstract
Ralstonia solanacearum, the causal agent of bacterial wilt, is a devastating plant pathogenic bacterium that infects more than 450 plant species. Until now, there has been no efficient control strategy against bacterial wilt. In this study, we screened a library of 100 plant-derived compounds for their antibacterial activity against R. solanacearum. Twelve compounds, including harmine, harmine hydrochloride, citral, vanillin, and vincamine, suppressed bacterial growth of R. solanacearum in liquid medium with an inhibition rate higher than 50%. Further focus on harmine revealed that the minimum inhibitory concentration of this compound is 120 mg/L. Treatment with 120 mg/L of harmine for 1 and 2 h killed more than 90% of bacteria. Harmine treatment suppressed the expression of the virulence-associated gene xpsR. Harmine also significantly inhibited biofilm formation by R. solanacearum at concentrations ranging from 20 mg/L to 60 mg/L. Furthermore, application of harmine effectively reduced bacterial wilt disease development in both tobacco and tomato plants. Collectively, our results demonstrate the great potential of plant-derived compounds as antibacterial agents against R. solanacearum, providing alternative ways for the efficient control of bacterial wilt.
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Affiliation(s)
- Hongkai Xia
- Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, China
- Research Institute of HNU in Chongqing, Chongqing, China
| | - Yanxia Huang
- Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, China
| | - Ruoyu Wu
- Department of Pathology and Pathophysiology, School of Medicine, Jishou University, Jishou, China
| | - Xin Tang
- Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, China
| | - Jun Cai
- Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, China
| | - Shun-xiang Li
- Hunan Engineering Technology Research Center for Bioactive Substance Discovery of Chinese Medicine, School of Pharmacy, Hunan University of Chinese Medicine, Changsha, China
| | - Lin Jiang
- Hunan Engineering Technology Research Center for Bioactive Substance Discovery of Chinese Medicine, School of Pharmacy, Hunan University of Chinese Medicine, Changsha, China
| | - Dousheng Wu
- Hunan Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, China
- Research Institute of HNU in Chongqing, Chongqing, China
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5
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Gao P, Qi K, Han Y, Ma L, Zhang B, Zhang Y, Guan X, Qi J. Effect of Trichoderma viride on rhizosphere microbial communities and biocontrol of soybean root rot. Front Microbiol 2023; 14:1204688. [PMID: 37333630 PMCID: PMC10272447 DOI: 10.3389/fmicb.2023.1204688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 05/15/2023] [Indexed: 06/20/2023] Open
Abstract
Biological seed dressing is a cost-effective means to protect plant roots from pathogens. Trichoderma is generally considered as one of the most common biological seed dressings. However, there is still a dearth of information on the effects of Trichoderma on microbial community of rhizosphere soil. High-throughput sequencing was used to analyze the effects of Trichoderma viride and a chemical fungicide on microbial community of soybean rhizosphere soil. The results showed that both T. viride and chemical fungicide could significantly reduce the disease index of soybean (15.11% for Trichoderma and 17.33% for Chemical), while no significant difference was observed between them. Both T. viride and chemical fungicide could affect the structure of rhizosphere microbial community, they increased the β-diversity of microbial community and significantly reduce the relative abundance of Saprotroph-Symbiotroph. Chemical fungicide could reduce the complexity and stability of co-occurrence network. However, T. viride is beneficial for maintaining network stability and increasing network complexity. There were 31 bacterial genera and 21 fungal genera significantly correlated with the disease index. Furthermore, several potential plant pathogenic microorganisms were also positively correlated with disease index, such as Fusarium, Aspergillus, Conocybe, Naganishia, and Monocillium. From this work, T. viride may be used as a substitute for chemical fungicide to control soybean root rot and be more friendly to soil microecology.
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Affiliation(s)
- Peixin Gao
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Kai Qi
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Yujuan Han
- Institute of Vegetables, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Liguo Ma
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Bo Zhang
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Yueli Zhang
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
| | - Xiumin Guan
- Shandong Agricultural Technology Extension Center, Jinan, China
| | - Junshan Qi
- Shandong Key Laboratory of Plant Virology, Institution of Plant Protection, Shandong Academy of Agricultural Sciences, Jinan, China
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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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7
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Cell Density-Regulated Adhesins Contribute to Early Disease Development and Adhesion in Ralstonia solanacearum. Appl Environ Microbiol 2023; 89:e0156522. [PMID: 36688670 PMCID: PMC9973027 DOI: 10.1128/aem.01565-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Adhesins (adhesive proteins) help bacteria stick to and colonize diverse surfaces and often contribute to virulence. The genome of the bacterial wilt pathogen Ralstonia solanacearum (Rs) encodes dozens of putative adhesins, some of which are upregulated during plant pathogenesis. Little is known about the role of these proteins in bacterial wilt disease. During tomato colonization, three putative Rs adhesin genes were upregulated in a ΔphcA quorum-sensing mutant that cannot respond to high cell densities: radA (Ralstonia adhesin A), rcpA (Ralstonia collagen-like protein A), and rcpB. Based on this differential gene expression, we hypothesized that adhesins repressed by PhcA contribute to early disease stages when Rs experiences a low cell density. During root colonization, Rs upregulated rcpA and rcpB, but not radA, relative to bacteria in the stem at mid-disease. Root attachment assays and confocal microscopy with ΔrcpA/B and ΔradA revealed that all three adhesins help Rs attach to tomato seedling roots. Biofilm assays on abiotic surfaces found that Rs does not require RadA, RcpA, or RcpB for interbacterial attachment (cohesion), but these proteins are essential for anchoring aggregates to a surface (adhesion). However, Rs did not require the adhesins for later disease stages in planta, including colonization of the root endosphere and stems. Interestingly, all three adhesins were essential for full competitive fitness in planta. Together, these infection stage-specific assays identified three proteins that contribute to adhesion and the critical first host-pathogen interaction in bacterial wilt disease. IMPORTANCE Every microbe must balance its need to attach to surfaces with the biological imperative to move and spread. The high-impact plant-pathogenic bacterium Ralstonia solanacearum can stick to biotic and abiotic substrates, presumably using some of the dozens of putative adhesins encoded in its genome. We confirmed the functions and identified the biological roles of multiple afimbrial adhesins. By assaying the competitive fitness and the success of adhesin mutants in three different plant compartments, we identified the specific disease stages and host tissues where three previously cryptic adhesins contribute to success in plants. Combined with tissue-specific regulatory data, this work indicates that R. solanacearum deploys distinct adhesins that help it succeed at different stages of plant pathogenesis.
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8
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Hayes MM, Dewberry RJ, Babujee L, Moritz R, Allen C. Validating Methods To Eradicate Plant-Pathogenic Ralstonia Strains Reveals that Growth In Planta Increases Bacterial Stress Tolerance. Microbiol Spectr 2022; 10:e0227022. [PMID: 36453936 PMCID: PMC9769772 DOI: 10.1128/spectrum.02270-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 11/14/2022] [Indexed: 12/03/2022] Open
Abstract
Plant-pathogenic bacteria in the Ralstonia solanacearum species complex (RSSC) cause highly destructive bacterial wilt disease of diverse crops. Wilt disease prevention and management is difficult because RSSC persists in soil, water, and plant material. Growers need practical methods to kill these pathogens in irrigation water, a common source of disease outbreaks. Additionally, the R. solanacearum race 3 biovar 2 (R3bv2) subgroup is a quarantine pest in many countries and a highly regulated select agent pathogen in the United States. Plant protection officials and researchers need validated protocols to eradicate R3bv2 for regulatory compliance. To meet these needs, we measured the survival of four R3bv2 and three phylotype I RSSC strains following treatment with hydrogen peroxide, stabilized hydrogen peroxide (Huwa-San), active chlorine, heat, UV radiation, and desiccation. No surviving RSSC cells were detected after cultured bacteria were exposed for 10 min to 400 ppm hydrogen peroxide, 50 ppm Huwa-San, 50 ppm active chlorine, or temperatures above 50°C. RSSC cells on agar plates were eradicated by 30 s of UV irradiation and killed by desiccation on most biotic and all abiotic surfaces tested. RSSC bacteria did not survive the cell lysis steps of four nucleic acid extraction protocols. However, bacteria in planta were more difficult to kill. Stems of infected tomato plants contained a subpopulation of bacteria with increased tolerance of heat and UV light, but not oxidative stress. This result has significant management implications. We demonstrate the utility of these protocols for compliance with select agent research regulations and for management of a bacterial wilt outbreak in the field. IMPORTANCE Bacteria in the Ralstonia solanacearum species complex (RSSC) are globally distributed and cause destructive vascular wilt diseases of many high-value crops. These aggressive pathogens spread in diseased plant material and via contaminated soil, tools, and irrigation water. A subgroup of the RSSC, race 3 biovar 2, is a European and Canadian quarantine pathogen and a U.S. select agent subject to stringent and constantly evolving regulations intended to prevent pathogen introduction or release. We validated eradication and inactivation methods that can be used by (i) growers seeking to disinfest water and manage bacterial wilt disease outbreaks, (ii) researchers who must remain in compliance with regulations, and (iii) regulators who are expected to define containment practices. Relevant to all these stakeholders, we show that while cultured RSSC cells are sensitive to relatively low levels of oxidative chemicals, desiccation, and heat, more aggressive treatment, such as autoclaving or incineration, is required to eradicate plant-pathogenic Ralstonia growing inside plant material.
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Affiliation(s)
- Madeline M. Hayes
- Department of Plant Pathology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Ronnie J. Dewberry
- Department of Plant Pathology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Lavanya Babujee
- Department of Plant Pathology, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Rebecca Moritz
- Select Agent Program, Environment, Health, and Safety, University of Wisconsin—Madison, Madison, Wisconsin, USA
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin—Madison, Madison, Wisconsin, USA
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9
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Extracellular DNAses Facilitate Antagonism and Coexistence in Bacterial Competitor-Sensing Interference Competition. Appl Environ Microbiol 2022; 88:e0143722. [PMID: 36374088 PMCID: PMC9746292 DOI: 10.1128/aem.01437-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Over the last 4 decades, the rate of discovery of novel antibiotics has decreased drastically, ending the era of fortuitous antibiotic discovery. A better understanding of the biology of bacteriogenic toxins potentially helps to prospect for new antibiotics. To initiate this line of research, we quantified antagonists from two different sites at two different depths of soil and found the relative number of antagonists to correlate with the bacterial load and carbon-to-nitrogen (C/N) ratio of the soil. Consecutive studies show the importance of antagonist interactions between soil isolates and the lack of a predicted role for nutrient availability and, therefore, support an in situ role in offense for the production of toxins in environments of high bacterial loads. In addition, the production of extracellular DNAses (exDNases) and the ability to antagonize correlate strongly. Using an in domum-developed probabilistic cellular automaton model, we studied the consequences of exDNase production for both coexistence and diversity within a dynamic equilibrium. Our model demonstrates that exDNase-producing isolates involved in amensal interactions act to stabilize a community, leading to increased coexistence within a competitor-sensing interference competition environment. Our results signify that the environmental and biological cues that control natural-product formation are important for understanding antagonism and community dynamics, structure, and function, permitting the development of directed searches and the use of these insights for drug discovery. IMPORTANCE Ever since the first observation of antagonism by microorganisms by Ernest Duchesne (E. Duchesne, Contribution à l'étude de la concurrence vitale chez les microorganisms. Antagonism entre les moisissures et les microbes, These pour obtenir le grade de docteur en medicine, Lyon, France, 1897), many scientists successfully identified and applied bacteriogenic bioactive compounds from soils to cure infection. Unfortunately, overuse of antibiotics and the emergence of clinical antibiotic resistance, combined with a lack of discovery, have hampered our ability to combat infections. A deeper understanding of the biology of toxins and the cues leading to their production may elevate the success rate of the much-needed discovery of novel antibiotics. We initiated this line of research and discovered that bacterial reciprocal antagonism is associated with exDNase production in isolates from environments with high bacterial loads, while diversity may increase in environments of lower bacterial loads.
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10
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Rivera-Zuluaga K, Hiles R, Barua P, Caldwell D, Iyer-Pascuzzi AS. Getting to the root of Ralstonia invasion. Semin Cell Dev Biol 2022; 148-149:3-12. [PMID: 36526528 DOI: 10.1016/j.semcdb.2022.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/01/2022] [Accepted: 12/05/2022] [Indexed: 12/16/2022]
Abstract
Plant diseases caused by soilborne pathogens are a major limiting factor in crop production. Bacterial wilt disease, caused by soilborne bacteria in the Ralstonia solanacearum Species Complex (Ralstonia), results in significant crop loss throughout the world. Ralstonia invades root systems and colonizes plant xylem, changing plant physiology and ultimately causing plant wilting in susceptible varieties. Elucidating how Ralstonia invades and colonizes plants is central to developing strategies for crop protection. Here we review Ralstonia pathogenesis from root detection and attachment, early root colonization, xylem invasion and subsequent wilting. We focus primarily on studies in tomato from the last 5-10 years. Recent work has identified elegant mechanisms Ralstonia uses to adapt to the plant xylem, and has discovered new genes that function in Ralstonia fitness in planta. A picture is emerging of an amazingly versatile pathogen that uses multiple strategies to make its surrounding environment more hospitable and can adapt to new environments.
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De La Fuente L, Merfa MV, Cobine PA, Coleman JJ. Pathogen Adaptation to the Xylem Environment. ANNUAL REVIEW OF PHYTOPATHOLOGY 2022; 60:163-186. [PMID: 35472277 DOI: 10.1146/annurev-phyto-021021-041716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A group of aggressive pathogens have evolved to colonize the plant xylem. In this vascular tissue, where water and nutrients are transported from the roots to the rest of the plant, pathogens must be able to thrive under acropetal xylem sap flow and scarcity of nutrients while having direct contact only with predominantly dead cells. Nevertheless, a few bacteria have adapted to exclusively live in the xylem, and various pathogens may colonize other plant niches without causing symptoms unless they reach the xylem. Once established, the pathogens modulate its physicochemical conditions to enhance their growth and virulence. Adaptation to the restrictive lifestyle of the xylem leads to genome reduction in xylem-restricted bacteria, as they have a higher proportion of pseudogenes in their genome. The basis of xylem adaptation is not completely understood; therefore, a need still exists for model systems to advance the knowledge on this topic.
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Affiliation(s)
- Leonardo De La Fuente
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA;
| | - Marcus V Merfa
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA;
| | - Paul A Cobine
- Department of Biological Sciences, Auburn University, Auburn, Alabama, USA
| | - Jeffrey J Coleman
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA;
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12
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MacIntyre AM, Meline V, Gorman Z, Augustine SP, Dye CJ, Hamilton CD, Iyer-Pascuzzi AS, Kolomiets MV, McCulloh KA, Allen C. Trehalose increases tomato drought tolerance, induces defenses, and increases resistance to bacterial wilt disease. PLoS One 2022; 17:e0266254. [PMID: 35476629 PMCID: PMC9045674 DOI: 10.1371/journal.pone.0266254] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Accepted: 03/16/2022] [Indexed: 12/13/2022] Open
Abstract
Ralstonia solanacearum causes bacterial wilt disease, leading to severe crop losses. Xylem sap from R. solanacearum-infected tomato is enriched in the disaccharide trehalose. Water-stressed plants also accumulate trehalose, which increases drought tolerance via abscisic acid (ABA) signaling. Because R. solanacearum-infected plants suffer reduced water flow, we hypothesized that bacterial wilt physiologically mimics drought stress, which trehalose could mitigate. We found that R. solanacearum-infected plants differentially expressed drought-associated genes, including those involved in ABA and trehalose metabolism, and had more ABA in xylem sap. Consistent with this, treating tomato roots with ABA reduced both stomatal conductance and stem colonization by R. solanacearum. Treating roots with trehalose increased xylem sap ABA and reduced plant water use by lowering stomatal conductance and temporarily improving water use efficiency. Trehalose treatment also upregulated expression of salicylic acid (SA)-dependent tomato defense genes; increased xylem sap levels of SA and other antimicrobial compounds; and increased bacterial wilt resistance of SA-insensitive NahG tomato plants. Additionally, trehalose treatment increased xylem concentrations of jasmonic acid and related oxylipins. Finally, trehalose-treated plants were substantially more resistant to bacterial wilt disease. Together, these data show that exogenous trehalose reduced both water stress and bacterial wilt disease and triggered systemic disease resistance, possibly through a Damage Associated Molecular Pattern (DAMP) response pathway. This suite of responses revealed unexpected linkages between plant responses to biotic and abiotic stress and suggested that R. solanacearum-infected plants increase trehalose to improve water use efficiency and increase wilt disease resistance. The pathogen may degrade trehalose to counter these efforts. Together, these results suggest that treating tomatoes with exogenous trehalose could be a practical strategy for bacterial wilt management.
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Affiliation(s)
- April M. MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Valerian Meline
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, United States of America
| | - Zachary Gorman
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, United States of America
| | - Steven P. Augustine
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Carolyn J. Dye
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Corri D. Hamilton
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Anjali S. Iyer-Pascuzzi
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, United States of America
| | - Michael V. Kolomiets
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, United States of America
| | - Katherine A. McCulloh
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI, United States of America
- * E-mail:
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13
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Ray JD, Subandiyah S, Rincón-Flórez VA, Prakoso AB, Carvalhais LC, Drenth A. Susceptibility of the Banana Inflorescence to Blood Disease. PHYTOPATHOLOGY 2022; 112:803-810. [PMID: 34636648 DOI: 10.1094/phyto-07-21-0311-r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The bacterium Ralstonia syzygii subsp. celebesensis causes Blood disease of banana, a vascular wilt of economic significance in Indonesia and Malaysia. Blood disease has expanded its geographic range in the last 20 years and is an emerging threat to Southeast Asian banana production. Many aspects of the disease cycle and biology are not well understood, including the ability of different parts of the female and male inflorescence of banana to act as infection courts. This study confirms that the banana varieties of Cavendish, and Kepok 'Kuning' are susceptible to Blood disease and that an inoculum concentration of 102 CFU/ml of R. syzygii subsp. celebesensis is adequate to initiate disease after pseudostem inoculation. Data show that infection occurs through both the male and female parts of a banana inflorescence and the rachis when snapped to remove the male bell. The infection courts are the female flowers, the male bell bract scar, the male bell flower cushion, the snapped rachis, and deflowered fingers. The location of these infection courts concurs with the dye studies demonstrating that dye externally applied to these plants parts enters the plant vascular system. Thus, the hypothesis is supported that infection of R. syzygii subsp. celebesensis occurs through open xylem vessels of the male and female parts of the banana inflorescence.
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Affiliation(s)
- Jane D Ray
- Centre for Horticultural Science, The University of Queensland, Brisbane 4001, Australia
| | - Siti Subandiyah
- Research Center for Biotechnology, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
- Department of Entomology and Plant Pathology, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
| | - Vivian A Rincón-Flórez
- Centre for Horticultural Science, The University of Queensland, Brisbane 4001, Australia
| | - Ady B Prakoso
- Department of Entomology and Plant Pathology, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
| | - Lilia C Carvalhais
- Centre for Horticultural Science, The University of Queensland, Brisbane 4001, Australia
| | - André Drenth
- Centre for Horticultural Science, The University of Queensland, Brisbane 4001, Australia
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14
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Laili N, Mukaihara T, Matsui H, Yamamoto M, Noutoshi Y, Toyoda K, Ichinose Y. Role of Trehalose Synthesis in Ralstonia syzygii subsp. indonesiensis PW1001 in Inducing Hypersensitive Response on Eggplant (Solanum melongena cv. Senryo-nigou). THE PLANT PATHOLOGY JOURNAL 2021; 37:566-579. [PMID: 34897249 PMCID: PMC8666247 DOI: 10.5423/ppj.oa.06.2021.0087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 10/08/2021] [Accepted: 10/12/2021] [Indexed: 06/14/2023]
Abstract
Ralstonia syzygii subsp. indonesiensis (Rsi, former name: Ralstonia solanacearum phylotype IV) PW1001, a causal agent of potato wilt disease, induces hypersensitive response (HR) on its non-host eggplant (Solanum melongena cv. Senryo-nigou). The disaccharide trehalose is involved in abiotic and biotic stress tolerance in many organisms. We found that trehalose is required for eliciting HR on eggplant by plant pathogen Rsi PW1001. In R. solanacearum, it is known that the OtsA/OtsB pathway is the dominant trehalose synthesis pathway, and otsA and otsB encode trehalose-6-phosphate (T6P) synthase and T6P phosphatase, respectively. We generated otsA and otsB mutant strains and found that these mutant strains reduced the bacterial trehalose concentration and HR induction on eggplant leaves compared to wild-type. Trehalose functions intracellularly in Rsi PW1001 because addition of exogenous trehalose did not affect the HR level and ion leakage. Requirement of trehalose in HR induction is not common in R. solanacearum species complex because mutation of otsA in Ralstonia pseudosolanacearum (former name: Ralstonia solanacearum phylotype I) RS1002 did not affect HR on the leaves of its non-host tobacco and wild eggplant Solanum torvum. Further, we also found that each otsA and otsB mutant had reduced ability to grow in a medium containing NaCl and sucrose, indicating that trehalose also has an important role in osmotic stress tolerance.
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Affiliation(s)
- Nur Laili
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
- Research Center for Biology, Research Organization for Life Sciences, National Research and Innovation Agency (BRIN), Jl. Raya Jakarta-Bogor Km. 46, Cibinong, Bogor, West Java 16911,
Indonesia
| | - Takafumi Mukaihara
- Research Institute for Biological Sciences, Okayama (RIBS), 7549-1 Yoshikawa, Kibichuo-cho, Okayama 716-1241,
Japan
| | - Hidenori Matsui
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
| | - Mikihiro Yamamoto
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
| | - Yoshiteru Noutoshi
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
| | - Kazuhiro Toyoda
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
| | - Yuki Ichinose
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Kita-ku, Okayama 700-8530,
Japan
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15
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Chambard M, Plasson C, Derambure C, Coutant S, Tournier I, Lefranc B, Leprince J, Kiefer-Meyer MC, Driouich A, Follet-Gueye ML, Boulogne I. New Insights into Plant Extracellular DNA. A Study in Soybean Root Extracellular Trap. Cells 2021; 10:E69. [PMID: 33466245 PMCID: PMC7824799 DOI: 10.3390/cells10010069] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/29/2020] [Accepted: 12/30/2020] [Indexed: 12/13/2022] Open
Abstract
exDNA is found in various organisms, including plants. However, plant exDNA has thus far received little attention related to its origin and role in the RET (root extracellular trap). In this study, we performed the first high-throughput genomic sequencing of plant exDNA from a Fabaceae with worldwide interest: soybean (Glycine max (L.) Merr.). The origin of this exDNA was first investigated in control condition, and the results show high-coverage on organelles (mitochondria/plastid) DNA relative to nuclear DNA, as well as a mix of coding and non-coding sequences. In the second part of this study, we investigated if exDNA release was modified during an elicitation with PEP-13 (a peptide elicitor from oomycete genus Phytophthora). Our results show that treatment of roots with PEP-13 does not affect the composition of exDNA.
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Affiliation(s)
- Marie Chambard
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Carole Plasson
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Céline Derambure
- Normandy Center for Genomic and Personalized Medicine, 76000 Rouen, France; (C.D.); (S.C.); (I.T.)
| | - Sophie Coutant
- Normandy Center for Genomic and Personalized Medicine, 76000 Rouen, France; (C.D.); (S.C.); (I.T.)
| | - Isabelle Tournier
- Normandy Center for Genomic and Personalized Medicine, 76000 Rouen, France; (C.D.); (S.C.); (I.T.)
| | - Benjamin Lefranc
- Plateforme de Recherche en Imagerie Cellulaire de Normandie (PRIMACEN), Normandie Université UNIROUEN, INSERM U1239, 76000 Rouen, France; (B.L.); (J.L.)
| | - Jérôme Leprince
- Plateforme de Recherche en Imagerie Cellulaire de Normandie (PRIMACEN), Normandie Université UNIROUEN, INSERM U1239, 76000 Rouen, France; (B.L.); (J.L.)
| | - Marie-Christine Kiefer-Meyer
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Azeddine Driouich
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Marie-Laure Follet-Gueye
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
| | - Isabelle Boulogne
- Normandie University, UNIROUEN, UFR des Sciences et Techniques, Glyco-MEV EA4358, SFR NORVEGE FED 4277, 76821 Mont-Saint-Aignan, France; (C.P.); (M.-C.K.-M.); (A.D.); (M.-L.F.-G.); (I.B.)
- Fédération de Recherche Normandie-Végétal, FED 4277, 76821 Mont-Saint-Aignan, France
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16
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Longchar B, Phukan T, Yadav S, Senthil‐Kumar M. An efficient low-cost xylem sap isolation method for bacterial wilt assays in tomato. APPLICATIONS IN PLANT SCIENCES 2020; 8:e11335. [PMID: 32351796 PMCID: PMC7186903 DOI: 10.1002/aps3.11335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 02/12/2020] [Indexed: 06/01/2023]
Abstract
PREMISE A portable, simple, yet efficient method was developed for the rapid extraction of xylem sap from the stems and petioles of tomato plants for diagnostic and quantification assays of the xylem-colonizing wilt bacterium Ralstonia solanacearum. METHODS AND RESULTS Xylem saps were extracted from tomato stem sections using negative pressure generated from handheld needleless syringes. The samples were collected from plants grown under different soil moisture levels at four days after inoculation with the pathogen. Pipette tips were modified to serve as adapters for the stem sections. The quantification of the bacterial load in the extracted sap was performed by plating sap dilutions in Kelman's triphenyltetrazolium chloride (TTC) medium. Pathogen identity was further confirmed by performing a PCR using R. solanacearum-specific primers. CONCLUSIONS Due to its simplicity, portability, and thoroughness of extraction from predetermined tissue sizes, the method can potentially facilitate high-throughput onsite sampling from a large number of samples in a short time, which cannot be achieved with other available techniques.
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Affiliation(s)
| | - Tarinee Phukan
- National Institute of Plant Genome Research, Aruna Asaf Ali MargNew Delhi110067India
| | - Sarita Yadav
- National Institute of Plant Genome Research, Aruna Asaf Ali MargNew Delhi110067India
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17
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MacIntyre AM, Barth JX, Pellitteri Hahn MC, Scarlett CO, Genin S, Allen C. Trehalose Synthesis Contributes to Osmotic Stress Tolerance and Virulence of the Bacterial Wilt Pathogen Ralstonia solanacearum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:462-473. [PMID: 31765286 DOI: 10.1094/mpmi-08-19-0218-r] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The xylem-dwelling plant pathogen Ralstonia solanacearum changes the chemical composition of host xylem sap during bacterial wilt disease. The disaccharide trehalose, implicated in stress tolerance across all kingdoms of life, is enriched in sap from R. solanacearum-infected tomato plants. Trehalose in xylem sap could be synthesized by the bacterium, the plant, or both. To investigate the source and role of trehalose metabolism during wilt disease, we evaluated the effects of deleting the three trehalose synthesis pathways in the pathogen: TreYZ, TreS, and OtsAB, as well as its sole trehalase, TreA. A quadruple treY/treS/otsA/treA mutant produced 30-fold less intracellular trehalose than the wild-type strain missing the trehalase enzyme. This trehalose-nonproducing mutant had reduced tolerance to osmotic stress, which the bacterium likely experiences in plant xylem vessels. Following naturalistic soil-soak inoculation of tomato plants, this triple mutant did not cause disease as well as wild-type R. solanacearum. Further, the wild-type strain out-competed the trehalose-nonproducing mutant by over 600-fold when tomato plants were coinoculated with both strains, showing that trehalose biosynthesis helps R. solanacearum overcome environmental stresses during infection. An otsA (trehalose-6-phosphate synthase) single mutant behaved similarly to ΔtreY/treS/otsA in all experimental settings, suggesting that the OtsAB pathway is the dominant trehalose synthesis pathway in R. solanacearum.
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Affiliation(s)
- April M MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, U.S.A
| | - John X Barth
- Department of Plant Pathology, University of Wisconsin-Madison, U.S.A
| | | | - Cameron O Scarlett
- Analytical Instrumentation Center, School of Pharmacy, University of Wisconsin-Madison
| | - Stéphane Genin
- LIPM, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, U.S.A
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18
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Ujita Y, Sakata M, Yoshihara A, Hikichi Y, Kai K. Signal Production and Response Specificity in the phc Quorum Sensing Systems of Ralstonia solanacearum Species Complex. ACS Chem Biol 2019; 14:2243-2251. [PMID: 31513382 DOI: 10.1021/acschembio.9b00553] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ralstonia solanacearum strains are devastating plant pathogens with global distribution, a wide host range, and genetic diversity, and they are now also referred to as the R. solanacearum species complex (RSSC). RSSC strains employ the quorum sensing (QS) system composed of the phcBSR operon to regulate their virulence on plants. The RSSC strains previously examined produce either (R)-methyl 3-hydroxymyristate (3-OH MAME) or (R)-methyl 3-hydroxypalmitate (3-OH PAME) as their QS signals. Analogously, the phylogenetic analyses of the signal synthase PhcB and the signal receptor PhcS from 15 RSSC strains revealed that these proteins have two clades dependent on their QS signal types. However, the biochemical mechanism underlying this selectivity of QS signal production remains to be elucidated. We demonstrated that the PhcB methyltransferases synthesize QS signals from the cognate fatty acids (R)-3-hydroxymyristic acid or (R)-3-hydroxypalmitic acid. The RSSC strains used here produced both fatty acids, and thus the selectivity of QS signal production depends on the activity of PhcB enzymes. On the other hand, the enantioselective supply of the precursors functioned in the production of enantiopure QS signals. The opposite QS signals weakly induced the production of virulence factors in the RSSC strains. Furthermore, the complementation of the phcB gene encoding the 3-OH PAME-type synthase to the phcB-deletion mutant of the 3-OH MAME-producing strain did not rescue its virulence on tomato plants. Taken together, we propose that the specific production of 3-OH MAME/3-OH PAME ensures full virulence of the RSSC strains.
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Affiliation(s)
- Yumeto Ujita
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Megumi Sakata
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Ayaka Yoshihara
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Yasufumi Hikichi
- Laboratory of Plant Pathology and Biotechnology, Kochi University, 200 Otsu, Monobe, Nankoku, Kochi, 783-8502, Japan
| | - Kenji Kai
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
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19
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Castillo JA, Agathos SN. A genome-wide scan for genes under balancing selection in the plant pathogen Ralstonia solanacearum. BMC Evol Biol 2019; 19:123. [PMID: 31208326 PMCID: PMC6580516 DOI: 10.1186/s12862-019-1456-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 06/10/2019] [Indexed: 02/07/2023] Open
Abstract
Background Plant pathogens are under significant selective pressure by the plant host. Consequently, they are expected to have adapted to this condition or contribute to evading plant defenses. In order to acquire long-term fitness, plant bacterial pathogens are usually forced to maintain advantageous genetic diversity in populations. This strategy ensures that different alleles in the pathogen’s gene pool are maintained in a population at frequencies larger than expected under neutral evolution. This selective process, known as balancing selection, is the subject of this work in the context of a common bacterial phytopathogen. We performed a genome-wide scan of Ralstonia solanacearum species complex, an aggressive plant bacterial pathogen that shows broad host range and causes a devastating disease called ‘bacterial wilt’. Results Using a sliding window approach, we analyzed 57 genomes from three phylotypes of the R. solanacearum species complex to detect signatures of balancing selection. A total of 161 windows showed extreme values in three summary statistics of population genetics: Tajima’s D, θw and Fu & Li’s D*. We discarded any confounding effects due to demographic events by means of coalescent simulations of genetic data. The prospective windows correspond to 78 genes with known function that map in any of the two main replicons (1.7% of total number of genes). The candidate genes under balancing selection are related to primary metabolism and other basal activities (51.3%) or directly associated to virulence (48.7%), the latter being involved in key functions targeted to dismantle plant defenses or to participate in critical stages in the pathogenic process. Conclusions We identified various genes under balancing selection that play a significant role in basic metabolism as well as in virulence of the R. solanacearum species complex. These genes are useful to understand and monitor the evolution of bacterial pathogen populations and emerge as potential candidates for future treatments to induce specific plant immune responses. Electronic supplementary material The online version of this article (10.1186/s12862-019-1456-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- José A Castillo
- School of Biological Sciences and Engineering, Yachay Tech University, Hacienda San Jose s/n and Proyecto Yachay, Urcuquí, Ecuador.
| | - Spiros N Agathos
- School of Biological Sciences and Engineering, Yachay Tech University, Hacienda San Jose s/n and Proyecto Yachay, Urcuquí, Ecuador
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20
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Huskey DA, Curlango‐Rivera G, Hawes MC. Use of rhodizonic acid for rapid detection of root border cell trapping of lead and reversal of trapping with DNase. APPLICATIONS IN PLANT SCIENCES 2019; 7:e01240. [PMID: 31024783 PMCID: PMC6476171 DOI: 10.1002/aps3.1240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/22/2019] [Indexed: 06/09/2023]
Abstract
PREMISE OF THE STUDY Lead (Pb) is a contaminant whose removal from soil remains a challenge. In a previous study, border cells released from root tips were found to trap Pb, alter its chemistry, and prevent root uptake. Rhodizonic acid (RA) is a forensic tool used to reveal gunshot residue, and also to detect Pb within plant tissues. Here we report preliminary observations to assess the potential application of RA in exploring the dynamics of Pb accumulation at the root tip surface. METHODS AND RESULTS Corn root tips were immersed in Pb solution, stained with RA, and observed microscopically. Pb trapping by border cells was evident within minutes. The role of extracellular DNA was revealed when addition of nucleases resulted in dispersal of RA-stained Pb particles. CONCLUSIONS RA is an efficient tool to monitor Pb-root interactions. Trapping by border cells may control Pb levels and chemistry at the root tip surface. Understanding how plants influence Pb distribution in soil may facilitate its remediation.
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Affiliation(s)
- David A. Huskey
- Department of Soil, Water and Environmental SciencesUniversity of Arizona429 Shantz Building, #38 1177 E. Fourth Street, P.O. Box 210038TucsonArizona85721‐0038USA
| | - Gilberto Curlango‐Rivera
- Department of Soil, Water and Environmental SciencesUniversity of Arizona429 Shantz Building, #38 1177 E. Fourth Street, P.O. Box 210038TucsonArizona85721‐0038USA
| | - Martha C. Hawes
- Department of Soil, Water and Environmental SciencesUniversity of Arizona429 Shantz Building, #38 1177 E. Fourth Street, P.O. Box 210038TucsonArizona85721‐0038USA
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21
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Khokhani D, Tran TM, Lowe-Power TM, Allen C. Plant Assays for Quantifying Ralstonia solanacearum Virulence. Bio Protoc 2018; 8:e3028. [PMID: 34395814 DOI: 10.21769/bioprotoc.3028] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 09/07/2018] [Accepted: 09/10/2018] [Indexed: 12/15/2022] Open
Abstract
Virulence assays are powerful tools to study microbial pathogenesis in vivo. Good assays track disease development and, coupled with targeted mutagenesis, can identify pathogen virulence factors. Disease development in plants is extremely sensitive to environmental factors such as temperature, atmospheric humidity, and soil water level, so it can be challenging to standardize conditions to achieve consistent results. Here, we present optimized and validated experimental conditions and analysis methods for nine assays that measure specific aspects of virulence in the phytopathogenic bacterium Ralstonia solanacearum, using tomato as the model host plant.
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Affiliation(s)
- Devanshi Khokhani
- Department of Bacteriology, University of Wisconsin-Madison, Madison, USA
| | - Tuan Minh Tran
- School of Biological Sciences, Nanyang Technological University, Singapore
| | | | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, USA
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22
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Binnenkade L, Kreienbaum M, Thormann KM. Characterization of ExeM, an Extracellular Nuclease of Shewanella oneidensis MR-1. Front Microbiol 2018; 9:1761. [PMID: 30123203 PMCID: PMC6085458 DOI: 10.3389/fmicb.2018.01761] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/13/2018] [Indexed: 01/08/2023] Open
Abstract
Bacterial extracellular nucleases have multiple functions in processes as diverse as nutrient acquisition, natural transformation, biofilm formation, or defense against neutrophil extracellular traps (NETs). Here we explored the properties of ExeM in Shewanella oneidensis MR-1, an extracellular nuclease, which is widely conserved among species of Shewanella, Vibrio, Aeromonas, and others. In S. oneidensis, ExeM is crucial for normal biofilm formation. In vitro activity measurements on heterologously produced ExeM revealed that this enzyme is a sugar-unspecific endonuclease, which requires Ca2+ and Mg2+/Mn2+ as co-factors for full activity. ExeM was almost exclusively localized to the cytoplasmic membrane fraction, even when a putative C-terminal membrane anchor was deleted. In contrast, ExeM was not detected in medium supernatants. Based on the results we hypothesize that ExeM predominantly interacts with DNA in close proximity to the cell, e.g., to promote biofilm formation and defense against NETs, or to control uptake of DNA.
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Affiliation(s)
- Lucas Binnenkade
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Maximilian Kreienbaum
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Kai M Thormann
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
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Costa OYA, Raaijmakers JM, Kuramae EE. Microbial Extracellular Polymeric Substances: Ecological Function and Impact on Soil Aggregation. Front Microbiol 2018; 9:1636. [PMID: 30083145 PMCID: PMC6064872 DOI: 10.3389/fmicb.2018.01636] [Citation(s) in RCA: 384] [Impact Index Per Article: 64.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 06/30/2018] [Indexed: 11/15/2022] Open
Abstract
A wide range of microorganisms produce extracellular polymeric substances (EPS), highly hydrated polymers that are mainly composed of polysaccharides, proteins, and DNA. EPS are fundamental for microbial life and provide an ideal environment for chemical reactions, nutrient entrapment, and protection against environmental stresses such as salinity and drought. Microbial EPS can enhance the aggregation of soil particles and benefit plants by maintaining the moisture of the environment and trapping nutrients. In addition, EPS have unique characteristics, such as biocompatibility, gelling, and thickening capabilities, with industrial applications. However, despite decades of research on the industrial potential of EPS, only a few polymers are widely used in different areas, especially in agriculture. This review provides an overview of current knowledge on the ecological functions of microbial EPSs and their application in agricultural soils to improve soil particle aggregation, an important factor for soil structure, health, and fertility.
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Affiliation(s)
- Ohana Y. A. Costa
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
- Institute of Biology, Leiden University, Leiden, Netherlands
| | - Jos M. Raaijmakers
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
- Institute of Biology, Leiden University, Leiden, Netherlands
| | - Eiko E. Kuramae
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
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24
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Lowe-Power TM, Khokhani D, Allen C. How Ralstonia solanacearum Exploits and Thrives in the Flowing Plant Xylem Environment. Trends Microbiol 2018; 26:929-942. [PMID: 29941188 DOI: 10.1016/j.tim.2018.06.002] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/24/2018] [Accepted: 06/04/2018] [Indexed: 10/28/2022]
Abstract
The plant wilt pathogen Ralstonia solanacearum thrives in the water-transporting xylem vessels of its host plants. Xylem is a relatively nutrient-poor, high-flow environment but R. solanacearum succeeds there by tuning its own metabolism and altering xylem sap biochemistry. Flow influences many traits that the bacterium requires for pathogenesis. Most notably, a quorum sensing system mediates the pathogen's major transition from a rapidly dividing early phase that voraciously consumes diverse food sources and avidly adheres to plant surfaces to a slower-growing late phase that can use fewer nutrients but produces virulence factors and disperses effectively. This review discusses recent findings about R. solanacearum pathogenesis in the context of its flowing in planta niche, with emphasis on R. solanacearum metabolism in plants.
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Affiliation(s)
- Tiffany M Lowe-Power
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA; Current address: Department of Plant and Microbial Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Devanshi Khokhani
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA; Current address: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA.
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25
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Wong SL, Wagner DD. Peptidylarginine deiminase 4: a nuclear button triggering neutrophil extracellular traps in inflammatory diseases and aging. FASEB J 2018; 32:fj201800691R. [PMID: 29924943 PMCID: PMC6219837 DOI: 10.1096/fj.201800691r] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 06/04/2018] [Indexed: 12/17/2022]
Abstract
Peptidylarginine deiminase 4 (PAD4) is a nuclear citrullinating enzyme that is critically involved in the release of decondensed chromatin from neutrophils as neutrophil extracellular traps (NETs). NETs, together with fibrin, are implicated in host defense against pathogens; however, the formation of NETs (NETosis) has injurious effects that may outweigh their protective role. For example, PAD4 activity produces citrullinated neoantigens that promote autoimmune diseases, such as rheumatoid arthritis, to which PAD4 is genetically linked and where NETosis is prominent. NETs are also generated in basic sterile inflammatory responses that are induced by many inflammatory stimuli, including cytokines, hypoxia, and activated platelets. Mice that lack PAD4-deficient in NETosis-serve as an excellent tool with which to study the importance of NETs in disease models. In recent years, animal and human studies have demonstrated that NETs contribute to the etiology and propagation of many common noninfectious diseases, the focus of our review. We will discuss the role of NETs in thrombotic and cardiovascular disease, the induction of NETs by cancers and its implications for cancer progression and cancer-associated thrombosis, and elevated NETosis in diabetes and its negative impact on wound healing, and will propose a link between PAD4/NETs and age-related organ fibrosis. We identify unresolved issues and new research directions.-Wong, S. L., Wagner, D. D. Peptidylarginine deiminase 4: a nuclear button triggering neutrophil extracellular traps in inflammatory diseases and aging.
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Affiliation(s)
- Siu Ling Wong
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Denisa D. Wagner
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
- Division of Hematology/Oncology, Boston Children’s Hospital, Boston, Massachusetts, USA
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26
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Castiblanco LF, Sundin GW. Cellulose production, activated by cyclic di-GMP through BcsA and BcsZ, is a virulence factor and an essential determinant of the three-dimensional architectures of biofilms formed by Erwinia amylovora Ea1189. MOLECULAR PLANT PATHOLOGY 2018; 19:90-103. [PMID: 27753193 PMCID: PMC6638026 DOI: 10.1111/mpp.12501] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 10/10/2016] [Accepted: 10/13/2016] [Indexed: 05/04/2023]
Abstract
Bacterial biofilms are multicellular aggregates encased in an extracellular matrix mainly composed of exopolysaccharides (EPSs), protein and nucleic acids, which determines the architecture of the biofilm. Erwinia amylovora Ea1189 forms a biofilm inside the xylem of its host, which results in vessel plugging and water transport impairment. The production of the EPSs amylovoran and levan is critical for the formation of a mature biofilm. In addition, cyclic dimeric GMP (c-di-GMP) has been reported to positively regulate amylovoran biosynthesis and biofilm formation in E. amylovora Ea1189. In this study, we demonstrate that cellulose is synthesized by E. amylovora Ea1189 and is a major modulator of the three-dimensional characteristics of biofilms formed by this bacterium, and also contributes to virulence during systemic host invasion. In addition, we demonstrate that the activation of cellulose biosynthesis in E. amylovora is a c-di-GMP-dependent process, through allosteric binding to the cellulose catalytic subunit BcsA. We also report that the endoglucanase BcsZ is a key player in c-di-GMP activation of cellulose biosynthesis. Our results provide evidence of the complex composition of the extracellular matrix produced by E. amylovora and the implications of cellulose biosynthesis in shaping the architecture of the biofilm and in the expression of one of the main virulence phenotypes of this pathogen.
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Affiliation(s)
- Luisa F. Castiblanco
- Department of Plant, Soil and Microbial Sciences and Center for Microbial PathogenesisMichigan State UniversityEast LansingMI48824USA
| | - George W. Sundin
- Department of Plant, Soil and Microbial Sciences and Center for Microbial PathogenesisMichigan State UniversityEast LansingMI48824USA
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27
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Sasse J, Martinoia E, Northen T. Feed Your Friends: Do Plant Exudates Shape the Root Microbiome? TRENDS IN PLANT SCIENCE 2018; 23:25-41. [PMID: 29050989 DOI: 10.1016/j.tplants.2017.09.003] [Citation(s) in RCA: 734] [Impact Index Per Article: 122.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/25/2017] [Accepted: 09/07/2017] [Indexed: 05/18/2023]
Abstract
Plant health in natural environments depends on interactions with complex and dynamic communities comprising macro- and microorganisms. While many studies have provided insights into the composition of rhizosphere microbiomes (rhizobiomes), little is known about whether plants shape their rhizobiomes. Here, we discuss physiological factors of plants that may govern plant-microbe interactions, focusing on root physiology and the role of root exudates. Given that only a few plant transport proteins are known to be involved in root metabolite export, we suggest novel families putatively involved in this process. Finally, building off of the features discussed in this review, and in analogy to well-known symbioses, we elaborate on a possible sequence of events governing rhizobiome assembly.
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Affiliation(s)
- Joelle Sasse
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Enrico Martinoia
- Department of Plant and Microbial Biology, University of Zurich, Zurich 8008, Switzerland
| | - Trent Northen
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Joint Genome Institute, Walnut Creek, CA 94958, USA.
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28
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Lowe-Power TM, Hendrich CG, von Roepenack-Lahaye E, Li B, Wu D, Mitra R, Dalsing BL, Ricca P, Naidoo J, Cook D, Jancewicz A, Masson P, Thomma B, Lahaye T, Michael AJ, Allen C. Metabolomics of tomato xylem sap during bacterial wilt reveals Ralstonia solanacearum produces abundant putrescine, a metabolite that accelerates wilt disease. Environ Microbiol 2017; 20:1330-1349. [PMID: 29215193 DOI: 10.1111/1462-2920.14020] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/29/2017] [Accepted: 12/03/2017] [Indexed: 12/20/2022]
Abstract
Ralstonia solanacearum thrives in plant xylem vessels and causes bacterial wilt disease despite the low nutrient content of xylem sap. We found that R. solanacearum manipulates its host to increase nutrients in tomato xylem sap, enabling it to grow better in sap from infected plants than in sap from healthy plants. Untargeted GC/MS metabolomics identified 22 metabolites enriched in R. solanacearum-infected sap. Eight of these could serve as sole carbon or nitrogen sources for R. solanacearum. Putrescine, a polyamine that is not a sole carbon or nitrogen source for R. solanacearum, was enriched 76-fold to 37 µM in R. solanacearum-infected sap. R. solanacearum synthesized putrescine via a SpeC ornithine decarboxylase. A ΔspeC mutant required ≥ 15 µM exogenous putrescine to grow and could not grow alone in xylem even when plants were treated with putrescine. However, co-inoculation with wildtype rescued ΔspeC growth, indicating R. solanacearum produced and exported putrescine to xylem sap. Intriguingly, treating plants with putrescine before inoculation accelerated wilt symptom development and R. solanacearum growth and systemic spread. Xylem putrescine concentration was unchanged in putrescine-treated plants, so the exogenous putrescine likely accelerated disease indirectly by affecting host physiology. These results indicate that putrescine is a pathogen-produced virulence metabolite.
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Affiliation(s)
- Tiffany M Lowe-Power
- Department of Plant Pathology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Connor G Hendrich
- Department of Plant Pathology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Edda von Roepenack-Lahaye
- Leibniz Institute of Plant Biochemistry, Zentrum für Molekularbiologie der Pflanzen (ZMBP), Universität Tübingen, Tübingen, Germany
| | - Bin Li
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Dousheng Wu
- Leibniz Institute of Plant Biochemistry, Zentrum für Molekularbiologie der Pflanzen (ZMBP), Universität Tübingen, Tübingen, Germany
| | - Raka Mitra
- Department of Biology, Carleton College, Northfield, MN 55057, USA
| | - Beth L Dalsing
- Department of Plant Pathology, University of Wisconsin - Madison, Madison, WI 53706, USA
| | - Patrizia Ricca
- Leibniz Institute of Plant Biochemistry, Zentrum für Molekularbiologie der Pflanzen (ZMBP), Universität Tübingen, Tübingen, Germany
| | - Jacinth Naidoo
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - David Cook
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
| | - Amy Jancewicz
- Department of Genetics, University of Wisconsin, Madison, Madison, WI 53706, USA
| | - Patrick Masson
- Department of Genetics, University of Wisconsin, Madison, Madison, WI 53706, USA
| | - Bart Thomma
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
| | - Thomas Lahaye
- Leibniz Institute of Plant Biochemistry, Zentrum für Molekularbiologie der Pflanzen (ZMBP), Universität Tübingen, Tübingen, Germany
| | - Anthony J Michael
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin - Madison, Madison, WI 53706, USA
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29
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A Single Regulator Mediates Strategic Switching between Attachment/Spread and Growth/Virulence in the Plant Pathogen Ralstonia solanacearum. mBio 2017; 8:mBio.00895-17. [PMID: 28951474 PMCID: PMC5615195 DOI: 10.1128/mbio.00895-17] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The PhcA virulence regulator in the vascular wilt pathogen Ralstonia solanacearum responds to cell density via quorum sensing. To understand the timing of traits that enable R. solanacearum to establish itself inside host plants, we created a ΔphcA mutant that is genetically locked in a low-cell-density condition. Comparing levels of gene expression of wild-type R. solanacearum and the ΔphcA mutant during tomato colonization revealed that the PhcA transcriptome includes an impressive 620 genes (>2-fold differentially expressed; false-discovery rate [FDR], ≤0.005). Many core metabolic pathways and nutrient transporters were upregulated in the ΔphcA mutant, which grew faster than the wild-type strain in tomato xylem sap and on dozens of specific metabolites, including 36 found in xylem. This suggests that PhcA helps R. solanacearum to survive in nutrient-poor environmental habitats and to grow rapidly during early pathogenesis. However, after R. solanacearum reaches high cell densities in planta, PhcA mediates a trade-off from maximizing growth to producing costly virulence factors. R. solanacearum infects through roots, and low-cell-density-mode-mimicking ΔphcA cells attached to tomato roots better than the wild-type cells, consistent with their increased expression of several adhesins. Inside xylem vessels, ΔphcA cells formed aberrantly dense mats. Possibly as a result, the mutant could not spread up or down tomato stems as well as the wild type. This suggests that aggregating improves R. solanacearum survival in soil and facilitates infection and that it reduces pathogenic fitness later in disease. Thus, PhcA mediates a second strategic switch between initial pathogen attachment and subsequent dispersal inside the host. PhcA helps R. solanacearum optimally invest resources and correctly sequence multiple steps in the bacterial wilt disease cycle. Ralstonia solanacearum is a destructive soilborne crop pathogen that wilts plants by colonizing their water-transporting xylem vessels. It produces its costly virulence factors only after it has grown to a high population density inside a host. To identify traits that this pathogen needs in other life stages, we studied a mutant that mimics the low-cell-density condition. This mutant (the ΔphcA mutant) cannot sense its own population density. It grew faster than and used many nutrients not available to the wild-type bacterium, including metabolites present in tomato xylem sap. The mutant also attached much better to tomato roots, and yet it failed to spread once it was inside plants because it was trapped in dense mats. Thus, PhcA helps R. solanacearum succeed over the course of its complex life cycle by ensuring avid attachment to plant surfaces and rapid growth early in disease, followed by high virulence and effective dispersal later in disease.
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30
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Boschi F, Schvartzman C, Murchio S, Ferreira V, Siri MI, Galván GA, Smoker M, Stransfeld L, Zipfel C, Vilaró FL, Dalla-Rizza M. Enhanced Bacterial Wilt Resistance in Potato Through Expression of Arabidopsis EFR and Introgression of Quantitative Resistance from Solanum commersonii. FRONTIERS IN PLANT SCIENCE 2017; 8:1642. [PMID: 29033958 PMCID: PMC5627020 DOI: 10.3389/fpls.2017.01642] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 09/07/2017] [Indexed: 05/09/2023]
Abstract
Bacterial wilt (BW) caused by Ralstonia solanacearum is responsible for substantial losses in cultivated potato (Solanum tuberosum) crops worldwide. Resistance genes have been identified in wild species; however, introduction of these through classical breeding has achieved only partial resistance, which has been linked to poor agronomic performance. The Arabidopsis thaliana (At) pattern recognition receptor elongation factor-Tu (EF-Tu) receptor (EFR) recognizes the bacterial pathogen-associated molecular pattern EF-Tu (and its derived peptide elf18) to confer anti-bacterial immunity. Previous work has shown that transfer of AtEFR into tomato confers increased resistance to R. solanacearum. Here, we evaluated whether the transgenic expression of AtEFR would similarly increase BW resistance in a commercial potato line (INIA Iporá), as well as in a breeding potato line (09509.6) in which quantitative resistance has been introgressed from the wild potato relative Solanum commersonii. Resistance to R. solanacearum was evaluated by damaged root inoculation under controlled conditions. Both INIA Iporá and 09509.6 potato lines expressing AtEFR showed greater resistance to R. solanacearum, with no detectable bacteria in tubers evaluated by multiplex-PCR and plate counting. Notably, AtEFR expression and the introgression of quantitative resistance from S. commersonii had a significant additive effect in 09509.6-AtEFR lines. These results show that the combination of heterologous expression of AtEFR with quantitative resistance introgressed from wild relatives is a promising strategy to develop BW resistance in potato.
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Affiliation(s)
| | - Claudia Schvartzman
- Unidad de Biotecnología, Instituto Nacional de Investigación AgropecuariaCanelones, Uruguay
| | - Sara Murchio
- Unidad de Biotecnología, Instituto Nacional de Investigación AgropecuariaCanelones, Uruguay
| | - Virginia Ferreira
- Departamento de Biociencias, Facultad de Química, Universidad de la RepúblicaMontevideo, Uruguay
| | - Maria I. Siri
- Departamento de Biociencias, Facultad de Química, Universidad de la RepúblicaMontevideo, Uruguay
| | - Guillermo A. Galván
- Departamento de Producción Vegetal, Centro Regional Sur, Facultad de Agronomía, Universidad de la RepúblicaCanelones, Uruguay
| | - Matthew Smoker
- The Sainsbury Laboratory, Norwich Research ParkNorwich, United Kingdom
| | - Lena Stransfeld
- The Sainsbury Laboratory, Norwich Research ParkNorwich, United Kingdom
| | - Cyril Zipfel
- The Sainsbury Laboratory, Norwich Research ParkNorwich, United Kingdom
| | - Francisco L. Vilaró
- Programa de Producción Hortícola, Instituto Nacional de Investigación AgropecuariaCanelones, Uruguay
| | - Marco Dalla-Rizza
- Unidad de Biotecnología, Instituto Nacional de Investigación AgropecuariaCanelones, Uruguay
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31
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Liu J, Sun L, Liu W, Guo L, Liu Z, Wei X, Ling J. A Nuclease from Streptococcus mutans Facilitates Biofilm Dispersal and Escape from Killing by Neutrophil Extracellular Traps. Front Cell Infect Microbiol 2017; 7:97. [PMID: 28401067 PMCID: PMC5368189 DOI: 10.3389/fcimb.2017.00097] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 03/13/2017] [Indexed: 02/02/2023] Open
Abstract
Streptococcus mutans is the primary etiologic agent of dental caries and occasionally infective endocarditis, with the ability to form biofilms and disperse cells into distal sites to exacerbate and spread infection. In this study, we identified a nuclease (DeoC) as a S. mutans biofilm dispersal modulating factor through microarray analysis. In vitro assays revealed a dispersal defect of a deoC deletion mutant, and functional studies with purified protein were indicative of the biofilm dispersal activity of DeoC. Neutrophils are a key host response factor restraining bacterial spreading through the formation of neutrophil extracellular traps (NETs), which consist of a nuclear DNA backbone associated with antimicrobial peptides. Therefore, we hypothesized that the dispersed S. mutans might utilize DeoC to degrade NETs and escape killing by the immune system. It was found that S. mutans induced NET formation upon contact with neutrophils, while the presence of NETs in turn enhanced the deoC expression of S. mutans. Fluorescence microscopy inspection showed that deoC deletion resulted in a decreased NET degradation ability of S. mutans and enhanced susceptibility to neutrophil killing. Data obtained from this study assigned two important roles for DeoC in S. mutans: contributing to the spread of infection through mediating biofilm dispersal, and facilitating the escape of S. mutans from neutrophil killing through NET degradation.
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Affiliation(s)
- Jia Liu
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Luping Sun
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Wei Liu
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Lihong Guo
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Zhaohui Liu
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Xi Wei
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
| | - Junqi Ling
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-Sen University Guangzhou, China
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32
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Leonard S, Hommais F, Nasser W, Reverchon S. Plant-phytopathogen interactions: bacterial responses to environmental and plant stimuli. Environ Microbiol 2017; 19:1689-1716. [DOI: 10.1111/1462-2920.13611] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 11/09/2016] [Accepted: 11/16/2016] [Indexed: 01/06/2023]
Affiliation(s)
- Simon Leonard
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - Florence Hommais
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - William Nasser
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
| | - Sylvie Reverchon
- University of Lyon, Université Claude Bernard Lyon 1; INSA-Lyon, CNRS, UMR5240, Microbiologie, Adaptation, Pathogénie, 10 rue Raphaël Dubois Villeurbanne F-69622 France
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