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Zhou T, Chen D, Li C, Sun Q, Li L, Liu F, Shen Q, Shen B. Isolation and characterization of Pseudomonas brassicacearum J12 as an antagonist against Ralstonia solanacearum and identification of its antimicrobial components. Microbiol Res 2012; 167:388-94. [PMID: 22361469 DOI: 10.1016/j.micres.2012.01.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 01/06/2012] [Accepted: 01/08/2012] [Indexed: 01/22/2023]
Abstract
A bacterial strain, J12, isolated from the rhizosphere soil of tomato plants strongly inhibited the growth of phytopathogenic bacteria Ralstonia solanacearum. Strain J12 was identified as Pseudomonas brassicacearum based on its 16S rRNA gene sequence. J12 could produce 2,4-diacetylphloroglucinol (2,4-DAPG), hydrogen cyanide (HCN), siderophore(s) and protease. The maximum growth and antagonistic activity were recorded at 30°C and pH 8. Glucose and tryptone were used as the most suitable carbon and nitrogen sources, respectively. Strain J12 significantly suppressed tomato bacteria wilt by 45.5% in the greenhouse experiment. The main antimicrobial compound of J12 was identified as 2,4-diacetylphloroglucinol (2,4-DAPG) by HPLC-ESI-MS analysis. The gene cluster phlACBD, which is responsible for 2,4-DAPG production, was identified and expressed in the bacterial strain Escherichia coli DH5α.
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Affiliation(s)
- Tiantian Zhou
- Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing 210095, China
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Couillerot O, Combes-Meynet E, Pothier JF, Bellvert F, Challita E, Poirier MA, Rohr R, Comte G, Moënne-Loccoz Y, Prigent-Combaret C. The role of the antimicrobial compound 2,4-diacetylphloroglucinol in the impact of biocontrol Pseudomonas fluorescens F113 on Azospirillum brasilense phytostimulators. Microbiology (Reading) 2011; 157:1694-1705. [DOI: 10.1099/mic.0.043943-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Pseudomonads producing the antimicrobial metabolite 2,4-diacetylphloroglucinol (Phl) can control soil-borne phytopathogens, but their impact on other plant-beneficial bacteria remains poorly documented. Here, the effects of synthetic Phl and Phl+
Pseudomonas fluorescens F113 on Azospirillum brasilense phytostimulators were investigated. Most A. brasilense strains were moderately sensitive to Phl. In vitro, Phl induced accumulation of carotenoids and poly-β-hydroxybutyrate-like granules, cytoplasmic membrane damage and growth inhibition in A. brasilense Cd. Experiments with P. fluorescens F113 and a Phl− mutant indicated that Phl production ability contributed to in vitro growth inhibition of A. brasilense Cd and Sp245. Under gnotobiotic conditions, each of the three strains, P. fluorescens F113 and A. brasilense Cd and Sp245, stimulated wheat growth. Co-inoculation of A. brasilense Sp245 and Pseudomonas resulted in the same level of phytostimulation as in single inoculations, whereas it abolished phytostimulation when A. brasilense Cd was used. Pseudomonas Phl production ability resulted in lower Azospirillum cell numbers per root system (based on colony counts) and restricted microscale root colonization of neighbouring Azospirillum cells (based on confocal microscopy), regardless of the A. brasilense strain used. Therefore, this work establishes that Phl+ pseudomonads have the potential to interfere with A. brasilense phytostimulators on roots and with their plant growth promotion capacity.
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Affiliation(s)
- Olivier Couillerot
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Emeline Combes-Meynet
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Joël F. Pothier
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Floriant Bellvert
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Elita Challita
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Marie-Andrée Poirier
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - René Rohr
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Gilles Comte
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Yvan Moënne-Loccoz
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
| | - Claire Prigent-Combaret
- CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France
- Université Lyon 1, Villeurbanne, France
- Université de Lyon, F-69622, Lyon, France
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Kidarsa TA, Goebel NC, Zabriskie TM, Loper JE. Phloroglucinol mediates cross-talk between the pyoluteorin and 2,4-diacetylphloroglucinol biosynthetic pathways in Pseudomonas fluorescens Pf-5. Mol Microbiol 2011; 81:395-414. [PMID: 21564338 DOI: 10.1111/j.1365-2958.2011.07697.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The antibiotics pyoluteorin and 2,4-diacetylphloroglucinol (DAPG) contribute to the biological control of soilborne plant diseases by some strains of Pseudomonas fluorescens, including Pf-5. These secondary metabolites also have signalling functions with each compound reported to induce its own production and repress the other's production. The first step in DAPG biosynthesis is production of phloroglucinol (PG) by PhlD. In this study, we show that PG is required at nanomolar concentrations for pyoluteorin production in Pf-5. At higher concentrations, PG is responsible for the inhibition of pyoluteorin production previously attributed to DAPG. DAPG had no effect on pyoluteorin production, and monoacetylphloroglucinol showed both stimulatory and inhibitory activities but at concentrations 100-fold greater than the levels of PG required for similar effects. We also demonstrate that PG regulates pyoluteorin production in P. aeruginosa and that a phlD gene adjacent to the pyoluteorin biosynthetic gene cluster in P. aeruginosa strain LESB58 can restore pyoluteorin biosynthesis to a ΔphlD mutant of Pf-5. Bioinformatic analyses show that the dual role of PhlD in the biosynthesis of DAPG and the regulation of pyoluteorin production could have arisen within the pseudomonads during the assembly of these biosynthetic gene clusters from genes and gene subclusters of diverse origins.
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Affiliation(s)
- Teresa A Kidarsa
- USDA-ARS-Horticultural Crops Research Laboratory, Corvallis, OR 97330, USA
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Jousset A, Rochat L, Lanoue A, Bonkowski M, Keel C, Scheu S. Plants respond to pathogen infection by enhancing the antifungal gene expression of root-associated bacteria. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:352-358. [PMID: 21077773 DOI: 10.1094/mpmi-09-10-0208] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens.
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Islam MT, von Tiedemann A. 2,4-Diacetylphloroglucinol suppresses zoosporogenesis and impairs motility of Peronosporomycete zoospores. World J Microbiol Biotechnol 2011; 27:2071-2079. [PMID: 22448105 PMCID: PMC3291839 DOI: 10.1007/s11274-011-0669-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 01/20/2011] [Indexed: 11/25/2022]
Abstract
2,4-Diacetylphloroglucinol (DAPG) produced by Pseudomonas fluorescens, shows toxicity to many microorganisms including fungi, bacteria, and peronosporomycetes. Zoosporogenesis and motility of zoospores are critical for a complete disease cycle and pathogenicity of the peronosporomycete phytopathogens. The aim of this study was to test the effects of DAPG and its derivatives on zoosporogenesis and motility of zoospores of a downy mildew pathogen, Plasmopara viticola, and a damping-off pathogen, Aphanomyces cochlioides. In both cases, DAPG inhibited zoosporogenesis (5 μg/ml) and the motility of zoospores (10 μg/ml) in a dose-dependent manner. Generally, zoospores became immotile shortly after exposure to DAPG followed by lysis. However, a fraction of DAPG treated A. cochlioides zoospores formed round cystospores instead of lysis and then germinated with excessively-branched germ tubes. All derivatives of DAPG had similar inhibitory activities but at varying doses. Among them, 2,4-dipropylphloroglucinol exerted the highest inhibitory activity against both zoosporogenesis and motility of zoospores. This revealed that the degree of hydrogen atoms substitution in the benzene ring by acyl groups and the length of substituted acyl groups were related to the level of bioactivity. This is the first report of inhibitory activities of DAPG and its derivatives against zoosporogenesis and motility of zoospores of two important peronosporomycete phytopathogens.
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Affiliation(s)
- M. Tofazzal Islam
- Division of Plant Pathology and Plant Protection, University of Göttingen, Grisebachstrasse 6, Göttingen, Germany
- Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, 1706 Bangladesh
| | - Andreas von Tiedemann
- Division of Plant Pathology and Plant Protection, University of Göttingen, Grisebachstrasse 6, Göttingen, Germany
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56
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Combes-Meynet E, Pothier JF, Moënne-Loccoz Y, Prigent-Combaret C. The Pseudomonas secondary metabolite 2,4-diacetylphloroglucinol is a signal inducing rhizoplane expression of Azospirillum genes involved in plant-growth promotion. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:271-84. [PMID: 21043573 DOI: 10.1094/mpmi-07-10-0148] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
During evolution, plants have become associated with guilds of plant-growth-promoting rhizobacteria (PGPR), which raises the possibility that individual PGPR populations may have developed mechanisms to cointeract with one another on plant roots. We hypothesize that this has resulted in signaling phenomena between different types of PGPR colonizing the same roots. Here, the objective was to determine whether the Pseudomonas secondary metabolite 2,4-diacetylphloroglucinol (DAPG) can act as a signal on Azospirillum PGPR and enhance the phytostimulation effects of the latter. On roots, the DAPG-producing Pseudomonas fluorescens F113 strain but not its phl-negative mutant enhanced the phytostimulatory effect of Azospirillum brasilense Sp245-Rif on wheat. Accordingly, DAPG enhanced Sp245-Rif traits involved in root colonization (cell motility, biofilm formation, and poly-β-hydroxybutyrate production) and phytostimulation (auxin production). A differential fluorescence induction promoter-trapping approach based on flow cytometry was then used to identify Sp245-Rif genes upregulated by DAPG. DAPG enhanced expression of a wide range of Sp245-Rif genes, including genes involved in phytostimulation. Four of them (i.e., ppdC, flgE, nirK, and nifX-nifB) tended to be upregulated on roots in the presence of P. fluorescens F113 compared with its phl-negative mutant. Our results indicate that DAPG can act as a signal by which some beneficial pseudomonads may stimulate plant-beneficial activities of Azospirillum PGPR.
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57
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Shanmugaiah V, Mathivanan N, Varghese B. Purification, crystal structure and antimicrobial activity of phenazine-1-carboxamide produced by a growth-promoting biocontrol bacterium,Pseudomonas aeruginosaMML2212. J Appl Microbiol 2010; 108:703-11. [DOI: 10.1111/j.1365-2672.2009.04466.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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58
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Islam MT, Fukushi Y. Growth inhibition and excessive branching in Aphanomyces cochlioides induced by 2,4-diacetylphloroglucinol is linked to disruption of filamentous actin cytoskeleton in the hyphae. World J Microbiol Biotechnol 2009; 26:1163-70. [DOI: 10.1007/s11274-009-0284-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 12/12/2009] [Indexed: 10/20/2022]
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59
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Gleeson O, O'Gara F, Morrissey JP. The Pseudomonas fluorescens secondary metabolite 2,4 diacetylphloroglucinol impairs mitochondrial function in Saccharomyces cerevisiae. Antonie van Leeuwenhoek 2009; 97:261-73. [PMID: 20091224 DOI: 10.1007/s10482-009-9407-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 12/10/2009] [Indexed: 11/25/2022]
Abstract
Pseudomonas fluorescens strains are known to produce a wide range of secondary metabolites including phenazines, siderophores, pyoluteorin, and 2,4 diacetylphloroglucinol (DAPG). DAPG is of particular interest because of its antifungal properties and because its production is associated with inhibition of phytopathogenic fungi in natural disease-suppressive soils. This trait has been exploited to develop strains of P. fluorescens that have potential application as biocontrol agents. Although the biochemistry, genetics and regulation of DAPG production have been well-studied, relatively little is known about how DAPG inhibits fungal growth and how fungi respond to DAPG. Employing a yeast model and a combination of phenotypic assays, molecular genetics and molecular physiological probes, we established that inhibition of fungal growth is caused by impairment of mitochondrial function. The effect of DAPG on yeast is largely fungistatic but DAPG also induces the formation of petite cells. Expression of the multidrug export proteins Pdr5p and Snq2p is increased by DAPG-treatment but this appears to be a secondary effect of mitochondrial damage as no role in enhancing DAPG-tolerance was identified for either Pdr5p or Snq2p.
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Affiliation(s)
- Olive Gleeson
- Department of Microbiology, University College Cork, Cork, Ireland
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60
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Lutz MP, Wenger S, Maurhofer M, Défago G, Duffy B. Signaling between bacterial and fungal biocontrol agents in a strain mixture. FEMS Microbiol Ecol 2009; 48:447-55. [PMID: 19712313 DOI: 10.1016/j.femsec.2004.03.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The use of bacterial and fungal strain mixtures is a promising way to improve efficacy of biocontrol treatments. Certain Pseudomonas and Trichoderma strains belong to the most common studied biocontrol agents. One key factor for the biocontrol efficacy of several P. fluorescens strains is the synthesis of 2,4-diacetylphloroglucinol (DAPG). Production of chitinases, such as the ECH42 endochitinase and the NAG1 N-acetyl-beta-d-glucosaminidase, is a primary mechanism of action for T. atroviride. We examined the molecular interactions between the DAPG-producing P. fluorescens strains CHA0 and Q2-87 and chitinase-producing T. atroviride P1. Interactions were monitored using the reporter gene constructs, phlA'-'lacZ translational fusion in P. fluorescens CHA0 and ech42-goxA or nag1-goxA fusions in T. atroviride P1. We found that DAPG enhanced nag1, but not ech42 expression, whereas an unidentified substance from P. fluorescens CHA0 repressed expression of both Trichoderma chitinases. Addition of T. atroviride P1 culture filtrates to growing cultures of P. fluorescens enhanced phlA expression transiently during growth. These results indicate that negative and positive effects on expression of key biocontrol genes may occur while mixing antagonists.
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Affiliation(s)
- Matthias P Lutz
- Institute of Plant Sciences, Swiss Federal Institute of Technology, Zürich, Switzerland
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61
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Mazurier S, Corberand T, Lemanceau P, Raaijmakers JM. Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt. ISME JOURNAL 2009; 3:977-91. [PMID: 19369971 DOI: 10.1038/ismej.2009.33] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Natural disease-suppressive soils provide an untapped resource for the discovery of novel beneficial microorganisms and traits. For most suppressive soils, however, the consortia of microorganisms and mechanisms involved in pathogen control are unknown. To date, soil suppressiveness to Fusarium wilt disease has been ascribed to carbon and iron competition between pathogenic Fusarium oxysporum and resident non-pathogenic F. oxysporum and fluorescent pseudomonads. In this study, the role of bacterial antibiosis in Fusarium wilt suppressiveness was assessed by comparing the densities, diversity and activity of fluorescent Pseudomonas species producing 2,4-diacetylphloroglucinol (DAPG) (phlD+) or phenazine (phzC+) antibiotics. The frequencies of phlD+ populations were similar in the suppressive and conducive soils but their genotypic diversity differed significantly. However, phlD genotypes from the two soils were equally effective in suppressing Fusarium wilt, either alone or in combination with non-pathogenic F. oxysporum strain Fo47. A mutant deficient in DAPG production provided a similar level of control as its parental strain, suggesting that this antibiotic does not play a major role. In contrast, phzC+ pseudomonads were only detected in the suppressive soil. Representative phzC+ isolates of five distinct genotypes did not suppress Fusarium wilt on their own, but acted synergistically in combination with strain Fo47. This increased level of disease suppression was ascribed to phenazine production as the phenazine-deficient mutant was not effective. These results suggest, for the first time, that redox-active phenazines produced by fluorescent pseudomonads contribute to the natural soil suppressiveness to Fusarium wilt disease and may act in synergy with carbon competition by resident non-pathogenic F. oxysporum.
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Affiliation(s)
- Sylvie Mazurier
- INRA, Université de Bourgogne, UMR 1229 Microbiologie des Sols et de l'Environnement, Dijon cedex, France
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62
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Brazelton JN, Pfeufer EE, Sweat TA, Gardener BBM, Coenen C. 2,4-diacetylphloroglucinol alters plant root development. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:1349-58. [PMID: 18785830 DOI: 10.1094/mpmi-21-10-1349] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Pseudomonas fluorescens isolates containing the phlD gene can protect crops from root pathogens, at least in part through production of the antibiotic 2,4-diacetylphloroglucinol (DAPG). However, the action mechanisms of DAPG are not fully understood, and effects of this antibiotic on host root systems have not been characterized in detail. DAPG inhibited primary root growth and stimulated lateral root production in tomato seedlings. Roots of the auxin-resistant diageotropica mutant of tomato demonstrated reduced DAPG sensitivity with regards to inhibition of primary root growth and induction of root branching. Additionally, applications of exogenous DAPG, at concentrations previously found in the rhizosphere of plants inoculated with DAPG-producing pseudomonads, inhibited the activation of an auxin-inducible GH3 promoter::luciferase reporter gene construct in transgenic tobacco hypocotyls. In this model system, supernatants of 17 phlD+ P. fluorescens isolates had inhibitory effects on luciferase activity similar to synthetic DAPG. In addition, a phlD() mutant strain, unable to produce DAPG, demonstrated delayed inhibitory effects compared with the parent wild-type strain. These results indicate that DAPG can alter crop root architecture by interacting with an auxin-dependent signaling pathway.
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63
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Schouten A, Maksimova O, Cuesta-Arenas Y, van den Berg G, Raaijmakers JM. Involvement of the ABC transporter BcAtrB and the laccase BcLCC2 in defence of Botrytis cinerea against the broad-spectrum antibiotic 2,4-diacetylphloroglucinol. Environ Microbiol 2008; 10:1145-57. [DOI: 10.1111/j.1462-2920.2007.01531.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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64
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Mammino L, Kabanda MM. Model structures for the study of acylated phloroglucinols and computational study of the caespitate molecule. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2006.10.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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65
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Weller DM, Landa BB, Mavrodi OV, Schroeder KL, De La Fuente L, Blouin Bankhead S, Allende Molar R, Bonsall RF, Mavrodi DV, Thomashow LS. Role of 2,4-diacetylphloroglucinol-producing fluorescent Pseudomonas spp. in the defense of plant roots. PLANT BIOLOGY (STUTTGART, GERMANY) 2007; 9:4-20. [PMID: 17058178 DOI: 10.1055/s-2006-924473] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Plants have evolved strategies of stimulating and supporting specific groups of antagonistic microorganisms in the rhizosphere as a defense against diseases caused by soilborne plant pathogens owing to a lack of genetic resistance to some of the most common and widespread soilborne pathogens. Some of the best examples of natural microbial defense of plant roots occur in disease suppressive soils. Soil suppressiveness against many different diseases has been described. Take-all is an important root disease of wheat, and soils become suppressive to take-all when wheat or barley is grown continuously in a field following a disease outbreak; this phenomenon is known as take-all decline (TAD). In Washington State, USA and The Netherlands, TAD results from the enrichment during monoculture of populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing Pseudomonas fluorescens to a density of 10 (5) CFU/g of root, the threshold required to suppress the take-all pathogen, Gaeumannomyces graminis var. tritici. 2,4-DAPG-producing P. fluorescens also are enriched by monoculture of other crops such as pea and flax, and evidence is accumulating that 2,4-DAPG producers contribute to the defense of plant roots in many different agroecosystems. At this time, 22 distinct genotypes of 2,4-DAPG producers (designated A - T, PfY and PfZ) have been defined by whole-cell repetitive sequence-based (rep)-PCR analysis, restriction fragment length polymorphism (RFLP) analysis of PHLD, and phylogenetic analysis of PHLD, but the number of genotypes is expected to increase. The genotype of an isolate is predictive of its rhizosphere competence on wheat and pea. Multiple genotypes often occur in a single soil and the crop species grown modulates the outcome of the competition among these genotypes in the rhizosphere. 2,4-DAPG producers are highly effective biocontrol agents against a variety of plant diseases and ideally suited for serving as vectors for expressing other biocontrol traits in the rhizosphere.
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Affiliation(s)
- D M Weller
- USDA-ARS Root Disease and Biological Control Research Unit, Washington State University, P.O. Box 646430, 367 Johnson Hall, Pullman, WA 99164-6430, USA.
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66
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Rezzonico F, Zala M, Keel C, Duffy B, Moënne-Loccoz Y, Défago G. Is the ability of biocontrol fluorescent pseudomonads to produce the antifungal metabolite 2,4-diacetylphloroglucinol really synonymous with higher plant protection? THE NEW PHYTOLOGIST 2007; 173:861-872. [PMID: 17286834 DOI: 10.1111/j.1469-8137.2006.01955.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The antifungal compound 2,4-diacetylphloroglucinol (Phl) contributes to biocontrol in pseudomonads, but whether or not Phl(+) biocontrol pseudomonads display higher plant-protecting activity than Phl(-) biocontrol pseudomonads remains to be demonstrated. This issue was addressed by assessing 230 biocontrol fluorescent pseudomonads selected from a collection of 3132 bacterial isolates obtained from 63 soils worldwide. One-third of the biocontrol pseudomonads were Phl(+) and almost all Phl(+) isolates also produced hydrogen cyanide (HCN). The only Phl(+) HCN(-) strain did harbor hcn genes, but with the deletion of a 134 bp hcnC fragment corresponding to an ADP-binding motif. Statistical analysis of biocontrol isolate distributions indicated that Phl production ability was associated with superior disease suppression activity in the Pythium-cucumber and Fusarium-tomato pathosystems, but this was also the case with HCN production ability. However, HCN significance was not as strong, as indicated both by the comparison of Phl(-) HCN(+) and Phl(-) HCN(-) strains and by correlation analyses. This is the first population-level demonstration of the higher plant-protecting activity of Phl(+) biocontrol pseudomonads in comparison with Phl(-) biocontrol pseudomonads.
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Affiliation(s)
- Fabio Rezzonico
- Phytopathology Group, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 2, CH-8092 Zürich, Switzerland
- SafeCrop Center, c/o Agroscope ACW Changins-Wädenswil, CH-8820 Wädenswil, Switzerland
| | - Marcello Zala
- Phytopathology Group, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 2, CH-8092 Zürich, Switzerland
| | - Christoph Keel
- Phytopathology Group, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 2, CH-8092 Zürich, Switzerland
- Département de Microbiologie Fondamentale, Université de Lausanne, CH-1015 Lausanne, Switzerland
| | - Brion Duffy
- Phytopathology Group, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 2, CH-8092 Zürich, Switzerland
- Agroscope ACW Changins-Wädenswil, CH-8820 Wädenswil, Switzerland
| | - Yvan Moënne-Loccoz
- Université de Lyon, Lyon, F-69003, France; Université Lyon 1, Lyon, F-69003, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, F-69622, France; IFR 41, Villeurbanne, F-69622, France
| | - Geneviève Défago
- Phytopathology Group, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 2, CH-8092 Zürich, Switzerland
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Jousset A, Lara E, Wall LG, Valverde C. Secondary metabolites help biocontrol strain Pseudomonas fluorescens CHA0 to escape protozoan grazing. Appl Environ Microbiol 2006; 72:7083-90. [PMID: 17088380 PMCID: PMC1636139 DOI: 10.1128/aem.00557-06] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 08/06/2006] [Indexed: 11/20/2022] Open
Abstract
In soil ecosystems, bacteria must cope with predation activity, which is attributed mainly to protists. The development of antipredation strategies may help bacteria maintain higher populations and persist longer in the soil. We analyzed the interaction between the root-colonizing and biocontrol strain Pseudomonas fluorescens CHA0 and three different protist isolates (an amoeba, a flagellate, and a ciliate). CHA0 produces a set of antibiotics, HCN, and an exoprotease. We observed that protists cannot grow on CHA0 but can multiply on isogenic regulatory mutants that do not produce the extracellular metabolites. The in vitro responses to CHA0 cells and its exoproducts included growth inhibition, encystation, paralysis, and cell lysis. By analyzing the responses of protists to bacterial supernatants obtained from different isogenic mutants whose production of one or more exometabolites was affected and also to culture extracts with antibiotic enrichment, we observed different contributions of the phenolic antifungal compound 2,4-diacetylphloroglucinol (DAPG) and the extracellular protease AprA to CHA0 toxicity for protists and to the encystation-reactivation cycle. The grazing pressure artificially produced by a mixture of the three protists in a microcosm system resulted in reduced colonization of cucumber roots by a regulatory isogenic CHA0 mutant unable to produce toxins. These results suggest that exometabolite production in biocontrol strain CHA0 may contribute to avoidance of protist grazing and help sustain higher populations in the rhizosphere, which may be a desirable and advantageous trait for competition with other bacteria for available resources.
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Affiliation(s)
- Alexandre Jousset
- Programa Prioritario sobre Interacciones Biológicas, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Provincia de Buenos Aires, Argentina
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De La Fuente L, Landa BB, Weller DM. Host Crop Affects Rhizosphere Colonization and Competitiveness of 2,4-Diacetylphloroglucinol-Producing Pseudomonas fluorescens. PHYTOPATHOLOGY 2006; 96:751-762. [PMID: 18943149 DOI: 10.1094/phyto-96-0751] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
ABSTRACT Strains of Pseudomonas fluorescens producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) are biocontrol agents which play a key role in the suppressiveness of some soils against soilborne pathogens. We evaluated the effect of the host plant genotype on rhizosphere colonization by both indigenous and introduced 2,4-DAPG-producing P. fluorescens. First, population densities of indigenous 2,4-DAPG producers in the rhizospheres of alfalfa, barley, bean, flax, lentil, lupine, oat, pea, and wheat grown in a Fusarium wilt-suppressive Puget silt loam were determined. Population densities differed among the various crops and among pea cultivars, with lentil and oat supporting the highest and lowest densities of 2,4-DAPG producers, respectively. Second, to determine the interactions among 2,4-DAPG producers in the rhizosphere, a Shano sandy loam was inoculated individually and with all possible combinations of P. fluorescens Q8r1-96 (genotype D), F113 (genotype K), and MVP1-4 (genotype P) and sown to wheat or pea, and the rhizosphere population dynamics of each strain was monitored. All three strains were similar in ability to colonize the rhizosphere of wheat and pea when introduced alone into the soil; however, when introduced together in equal densities, the outcome of the interactions differed according to the host crop. In the wheat rhizosphere, the population density of strain F113 was significantly greater than that of Q8r1-96 in the mixed inoculation studies, but no significant differences were observed on pea. The population density of strain Q8r1-96 was greater than that of MVP1-4 in the mixed inoculation on wheat, but the opposite occurred on pea. In the wheat rhizosphere, the population of MVP1-4 dropped below the detection limit (log 3.26 CFU g(-1) of root) in the presence of F113; however, on pea, the population density of MVP1-4 was higher than that of F113. When all three strains were present together, F113 had the greatest density in the wheat rhizosphere, but MVP1-4 was dominant in the pea rhizosphere. Finally, eight pea cultivars were grown in soil inoculated with either MVP1-4 or Q8r1-96. The effect of the pea cultivar on rhizosphere colonization was dependent on the bacterial strain inoculated. Rhizosphere population densities of MVP1-4 did not differ significantly among pea cultivars, whereas population densities of Q8r1-96 did. We conclude from these studies that the host crop plays a key role in modulating both rhizosphere colonization by 2,4-DAPG-producing P. fluorescens and the interactions among different genotypes present in the same rhizosphere.
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Velusamy P, Immanuel JE, Gnanamanickam SS, Thomashow L. Biological control of rice bacterial blight by plant-associated bacteria producing 2,4-diacetylphloroglucinol. Can J Microbiol 2006; 52:56-65. [PMID: 16541159 DOI: 10.1139/w05-106] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Certain plant-associated strains of fluorescent Pseudomonas spp. are known to produce the antimicrobial antibiotic 2,4-diacetylphloroglucinol (DAPG). It has antibacterial, antifungal, antiviral, and antihelminthic properties and has played a significant role in the biological control of tobacco, wheat, and sugar beet diseases. It has never been reported from India and has not been implicated in the biological suppression of a major disease of the rice crop. Here, we report that a subpopulation of 27 strains of plant-associated Pseudomonas fluorescens screened in a batch of 278 strains of fluorescent pseudomonads produced DAPG. The DAPG production was detected by a PCR-based screening method that used primers Phl2a and Phl2b and amplified a 745-bp fragment characteristic of DAPG. HPLC, 1H NMR, and IR analyses provided further evidence for its production. We report also that this compound inhibited the growth of the devastating rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae in laboratory assays and suppressed rice bacterial blight up to 59%-64% in net-house and field experiments. Tn5 mutants defective in DAPG production (Phl-) of P. fluorescens PTB 9 were much less effective in their suppression of rice bacterial blight.
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McSpadden Gardener BB, Gutierrez LJ, Joshi R, Edema R, Lutton E. Distribution and Biocontrol Potential of phlD(+) Pseudomonads in Corn and Soybean Fields. PHYTOPATHOLOGY 2005; 95:715-24. [PMID: 18943789 DOI: 10.1094/phyto-95-0715] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
ABSTRACT The abundance and diversity of phlD(+) Pseudomonas spp. colonizing the rhizospheres of young, field-grown corn and soybean plants were assayed over a 3-year period. Populations of these bacteria were detected on the large majority of plants sampled in the state of Ohio, but colonization was greater on corn. Although significant variation in the incidence of rhizosphere colonization was observed from site to site and year to year on both crops, the magnitude of the variation was greatest for soybean. The D genotype was detected on plants collected from all 15 counties examined, and it represented the most abundant subpopulation on both crops. Additionally, six other genotypes (A, C, F, I, R, and S) were found to predominate in the rhizosphere of some plants. The most frequently observed of these were the A genotype and a newly discovered S genotype, both of which were found on corn and soybean roots obtained from multiple locations. Multiple isolates of the most abundant genotypes were recovered and characterized. The S genotype was found to be phylogenetically and phenotypically similar to the D genotype. In addition, the novel R genotype was found to be most similar to the A genotype. All of the isolates displayed significant capacities to inhibit the growth of an oomycete pathogen in vitro, but such phenotypes were highly dependent on media used. When tested against multiple oomycete pathogens isolated from soybean, the A genotype was significantly more inhibitory than the D genotype when incubated on 1/10x tryptic soy agar and 1/5x corn meal agar. Seed inoculation with different isolates of the A, D, and S genotypes indicated that significant root colonization, generally in excess of log 5 cells per gram of root, could be attained on both crops. Field trials of the A genotype isolate Wayne1R indicated the capacity of inoculant populations to supplement the activities of native populations so as to increase soybean stands and yields. The relevance of these findings to natural and augmentative biocontrol of root pathogens by these bacteria is discussed.
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Abstract
Particular bacterial strains in certain natural environments prevent infectious diseases of plant roots. How these bacteria achieve this protection from pathogenic fungi has been analysed in detail in biocontrol strains of fluorescent pseudomonads. During root colonization, these bacteria produce antifungal antibiotics, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, biocontrol bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels.
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Affiliation(s)
- Dieter Haas
- Department of Fundamental Microbiology, University of Lausanne, CH-1015 Lausanne, Switzerland.
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Bergsma-Vlami M, Prins ME, Raaijmakers JM. Influence of plant species on population dynamics, genotypic diversity and antibiotic production in the rhizosphere by indigenous Pseudomonas spp. FEMS Microbiol Ecol 2004; 52:59-69. [PMID: 16329893 DOI: 10.1016/j.femsec.2004.10.007] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2004] [Revised: 09/02/2004] [Accepted: 10/21/2004] [Indexed: 11/25/2022] Open
Abstract
The population dynamics, genotypic diversity and activity of naturally-occurring 2,4-diacetylphloroglucinol (DAPG)-producing Pseudomonas spp. was investigated for four plant species (wheat, sugar beet, potato, lily) grown in two different soils. All four plant species tested, except lily and in some cases wheat, supported relatively high rhizosphere populations (5 x 10(4) to 1 x 10(6) CFU/g root) of indigenous DAPG-producing Pseudomonas spp. during successive cultivation in both a take-all suppressive and a take-all conducive soil. Although lily supported on average the highest population densities of fluorescent Pseudomonas spp., it was the least supportive of DAPG-producing Pseudomonas spp. of all four plant species. The genotypic diversity of 492 DAPG-producing Pseudomonas isolates, assessed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis of the phlD gene, revealed a total of 7 genotypes. Some of the genotypes were found only in the rhizosphere of a specific plant, whereas the predominant genotypes were found at significantly higher frequencies in the rhizosphere of three plant species (wheat, sugar beet and potato). Statistical analysis of the phlD(+) genotype frequencies showed that the diversity of the phlD(+) isolates from lily was significantly lower than the diversity of phlD(+) isolates found on wheat, sugar beet or potato. Additionally, soil type had a significant effect on both the phlD(+) population density and the phlD(+) genotype frequencies, with the take-all suppressive soil being the most supportive. HPLC analysis further showed that the plant species had a significant effect on DAPG-production by the indigenous phlD(+) population: the wheat and potato rhizospheres supported significantly higher amounts of DAPG produced per cell basis than the rhizospheres of sugar beet and lily. Collectively, the results of this study showed that the host plant species has a significant influence on the dynamics, composition and activity of specific indigenous antagonistic Pseudomonas spp.
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Affiliation(s)
- Maria Bergsma-Vlami
- Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, P.O. Box 8025, 6709, PD Wageningen, The Netherlands
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Schouten A, van den Berg G, Edel-Hermann V, Steinberg C, Gautheron N, Alabouvette C, de Vos CH, Lemanceau P, Raaijmakers JM. Defense responses of Fusarium oxysporum to 2,4-diacetylphloroglucinol, a broad-spectrum antibiotic produced by Pseudomonas fluorescens. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:1201-1211. [PMID: 15559985 DOI: 10.1094/mpmi.2004.17.11.1201] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A collection of 76 plant-pathogenic and 41 saprophytic Fusarium oxysporum strains was screened for sensitivity to 2,4-diacetylphloroglucinol (2,4-DAPG), a broad-spectrum antibiotic produced by multiple strains of antagonistic Pseudomonas fluorescens. Approximately 17% of the F. oxysporum strains were relatively tolerant to high 2,4-DAPG concentrations. Tolerance to 2,4-DAPG did not correlate with the geographic origin of the strains, formae speciales, intergenic spacer (IGS) group, or fusaric acid production levels. Biochemical analysis showed that 18 of 20 tolerant F. oxysporum strains were capable of metabolizing 2,4-DAPG. For two tolerant strains, analysis by mass spectrometry indicated that deacetylation of 2,4-DAPG to the less fungitoxic derivatives monoacetylphloroglucinol and phloroglucinol is among the initial mechanisms of 2,4-DAPG degradation. Production of fusaric acid, a known inhibitor of 2,4-DAPG biosynthesis in P. fluorescens, differed considerably among both 2,4-DAPG-sensitive and -tolerant F. oxysporum strains, indicating that fusaric acid production may be as important for 2,4-DAPG-sensitive as for -tolerant F. oxysporum strains. Whether 2,4-DAPG triggers fusaric acid production was studied for six F. oxysporum strains; 2,4-DAPG had no significant effect on fusaric acid production in four strains. In two strains, however, sublethal concentrations of 2,4-DAPG either enhanced or significantly decreased fusaric acid production. The implications of 2,4-DAPG degradation, the distribution of this trait within F. oxysporum and other plant-pathogenic fungi, and the consequences for the efficacy of biological control are discussed.
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Affiliation(s)
- Alexander Schouten
- Laboratory of Phytopathology, Plant Sciences Department, Wageningen University, 6700 EE Wageningen, The Netherlands.
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Duffy B, Keel C, Défago G. Potential role of pathogen signaling in multitrophic plant-microbe interactions involved in disease protection. Appl Environ Microbiol 2004; 70:1836-42. [PMID: 15006813 PMCID: PMC368418 DOI: 10.1128/aem.70.3.1836-1842.2004] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2002] [Accepted: 11/25/2003] [Indexed: 11/20/2022] Open
Abstract
Multitrophic interactions mediate the ability of fungal pathogens to cause plant disease and the ability of bacterial antagonists to suppress disease. Antibiotic production by antagonists, which contributes to disease suppression, is known to be modulated by abiotic and host plant environmental conditions. Here, we demonstrate that a pathogen metabolite functions as a negative signal for bacterial antibiotic biosynthesis, which can determine the relative importance of biological control mechanisms available to antagonists and which may also influence fungus-bacterium ecological interactions. We found that production of the polyketide antibiotic 2,4-diacetylphloroglucinol (DAPG) was the primary biocontrol mechanism of Pseudomonas fluorescens strain Q2-87 against Fusarium oxysporum f. sp. radicis-lycopersici on the tomato as determined with mutational analysis. In contrast, DAPG was not important for the less-disease-suppressive strain CHA0. This was explained by differential sensitivity of the bacteria to fusaric acid, a pathogen phyto- and mycotoxin that specifically blocked DAPG biosynthesis in strain CHA0 but not in strain Q2-87. In CHA0, hydrogen cyanide, a biocide not repressed by fusaric acid, played a more important role in disease suppression.
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Affiliation(s)
- Brion Duffy
- Swiss Federal Research Institute for Fruit Production, Viticulture and Horticulture, CH-8820 Wädenswil, Switzerland.
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