601
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Talboys PJ, Owen DW, Healey JR, Withers PJA, Jones DL. Auxin secretion by Bacillus amyloliquefaciens FZB42 both stimulates root exudation and limits phosphorus uptake in Triticum aestivium. BMC PLANT BIOLOGY 2014; 14:51. [PMID: 24558978 PMCID: PMC4015440 DOI: 10.1186/1471-2229-14-51] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 02/12/2014] [Indexed: 05/09/2023]
Abstract
BACKGROUND The use of auxin-producing rhizosphere bacteria as agricultural products promises increased root production and therefore greater phosphate (Pi) uptake. Whilst such bacteria promote root production in vitro, the nature of the bacteria-plant interaction in live soil, particularly concerning any effects on nutrient uptake, are not known. This study uses Bacillus amyloliquefaciens FZB42, an auxin-producing rhizobacterium, as a dressing on Triticum aestivium seeds. It then examines the effects on root production, Pi uptake, Pi-related gene expression and organic carbon (C) exudation. RESULTS Seed treatment with B. amyloliquefaciens FZB42 increased root production at low environmental Pi concentrations, but significantly repressed root Pi uptake. This coincided with an auxin-mediated reduction in expression of the Pi transporters TaPHT1.8 and TaPHT1.10. Applied exogenous auxin also triggered an increase in root C exudation. At high external Pi concentrations, root production was promoted by B. amyloliquefaciens FZB42, but Pi uptake was unaffected. CONCLUSIONS We conclude that, alongside promoting root production, auxin biosynthesis by B. amyloliquefaciens FZB42 both re-models Pi transporter expression and elevates organic C exudation. This shows the potential importance of rhizobacterial-derived auxin following colonisation of root surfaces, and the nature of this bacteria-plant interaction in soil.
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Affiliation(s)
- Peter J Talboys
- School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK
| | - Darren W Owen
- School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK
| | - John R Healey
- School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK
| | - Paul JA Withers
- School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK
| | - David L Jones
- School of Environment, Natural Resources and Geography, College of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2DG, UK
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602
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The bacterial effector HopX1 targets JAZ transcriptional repressors to activate jasmonate signaling and promote infection in Arabidopsis. PLoS Biol 2014; 12:e1001792. [PMID: 24558350 PMCID: PMC3928049 DOI: 10.1371/journal.pbio.1001792] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 01/09/2014] [Indexed: 11/19/2022] Open
Abstract
Pathogenicity of Pseudomonas syringae is dependent on a type III secretion system, which secretes a suite of virulence effector proteins into the host cytoplasm, and the production of a number of toxins such as coronatine (COR), which is a mimic of the plant hormone jasmonate-isoleuce (JA-Ile). Inside the plant cell, effectors target host molecules to subvert the host cell physiology and disrupt defenses. However, despite the fact that elucidating effector action is essential to understanding bacterial pathogenesis, the molecular function and host targets of the vast majority of effectors remain largely unknown. Here, we found that effector HopX1 from Pseudomonas syringae pv. tabaci (Pta) 11528, a strain that does not produce COR, interacts with and promotes the degradation of JAZ proteins, a key family of JA-repressors. We show that hopX1 encodes a cysteine protease, activity that is required for degradation of JAZs by HopX1. HopX1 associates with JAZ proteins through its central ZIM domain and degradation occurs in a COI1-independent manner. Moreover, ectopic expression of HopX1 in Arabidopsis induces the expression of JA-dependent genes, represses salicylic acid (SA)-induced markers, and complements the growth of a COR-deficient P. syringae pv. tomato (Pto) DC3000 strain during natural bacterial infections. Furthermore, HopX1 promoted susceptibility when delivered by the natural type III secretion system, to a similar extent as the addition of COR, and this effect was dependent on its catalytic activity. Altogether, our results indicate that JAZ proteins are direct targets of bacterial effectors to promote activation of JA-induced defenses and susceptibility in Arabidopsis. HopX1 illustrates a paradigm of an alternative evolutionary solution to COR with similar physiological outcome.
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603
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Mohammed M, Ch S, Ch RV. Aniline is an inducer, and not a precursor, for indole derivatives in Rubrivivax benzoatilyticus JA2. PLoS One 2014; 9:e87503. [PMID: 24533057 PMCID: PMC3922755 DOI: 10.1371/journal.pone.0087503] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 12/27/2013] [Indexed: 11/19/2022] Open
Abstract
Rubrivivax benzoatilyticus JA2 and other anoxygenic photosynthetic bacteria produce indole derivatives when exposed to aniline, a xenobiotic compound. Though this phenomenon has been reported previously, the role of aniline in the production of indoles is still a biochemical riddle. The present study aims at understanding the specific role of aniline (as precursor or stimulator) in the production of indoles and elucidating the biochemical pathway of indoles in aniline-exposed cells by using stable isotope approaches. Metabolic profiling revealed tryptophan accumulation only in aniline exposed cells along with indole 3-acetic acid (IAA) and indole 3-aldehyde (IAld), the two major catabolites of tryptophan. Deuterium labelled aniline feeding studies revealed that aniline is not a precursor of indoles in strain JA2. Further, production of indoles only in aniline-exposed cells suggests that aniline is an indoles stimulator. In addition, production of indoles depended on the presence of a carbon source, and production enhanced when carbon sources were added to the culture. Isotope labelled fumarate feeding identified, fumarate as the precursor of indole, indicating de novo synthesis of indoles. Glyphosate (shikimate pathway inhibitor) inhibited the indoles production, accumulation of tryptophan, IAA and IAld indicating that indoles synthesis in strain JA2 occurs via the de novo shikimate pathway. The up-regulation of anthranilate synthase gene and induction of anthranilate synthase activity correlated well with tryptophan production in strain JA2. Induction of tryptophan aminotransferase and tryptophan 2-monooxygenase activities corroborated well with IAA levels, suggesting that tryptophan catabolism occurs simultaneously in aniline exposed cells. Our study demonstrates that aniline (stress) stimulates tryptophan/indoles synthesis via the shikimate pathway by possibly modulating the metabolic pathway.
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Affiliation(s)
- Mujahid Mohammed
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Sasikala Ch
- Bacterial Discovery Laboratory, Centre for Environment, IST, J NT University Hyderabad, Kukatpally, Hyderabad, India
| | - Ramana V. Ch
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
- * E-mail:
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604
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Kim K, Jang YJ, Lee SM, Oh BT, Chae JC, Lee KJ. Alleviation of salt stress by enterobacter sp. EJ01 in tomato and Arabidopsis is accompanied by up-regulation of conserved salinity responsive factors in plants. Mol Cells 2014; 37:109-17. [PMID: 24598995 PMCID: PMC3935623 DOI: 10.14348/molcells.2014.2239] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 12/16/2013] [Accepted: 12/18/2013] [Indexed: 11/27/2022] Open
Abstract
Microbiota in the niches of the rhizosphere zones can affect plant growth and responses to environmental stress conditions via mutualistic interactions with host plants. Specifically, some beneficial bacteria, collectively referred to as Plant Growth Promoting Rhizobacteria (PGPRs), increase plant biomass and innate immunity potential. Here, we report that Enterobacter sp. EJ01, a bacterium isolated from sea china pink (Dianthus japonicus thunb) in reclaimed land of Gyehwa-do in Korea, improved the vegetative growth and alleviated salt stress in tomato and Arabidopsis. EJ01 was capable of producing 1-aminocy-clopropane-1-carboxylate (ACC) deaminase and also exhibited indole-3-acetic acid (IAA) production. The isolate EJ01 conferred increases in fresh weight, dry weight, and plant height of tomato and Arabidopsis under both normal and high salinity conditions. At the molecular level, short-term treatment with EJ01 increased the expression of salt stress responsive genes such as DREB2b, RD29A, RD29B, and RAB18 in Arabidopsis. The expression of proline biosynthetic genes (i.e. P5CS1 and P5CS2) and of genes related to priming processes (i.e. MPK3 and MPK6) were also up-regulated. In addition, reactive oxygen species scavenging activities were enhanced in tomatoes treated with EJ01 in stressed conditions. GFP-tagged EJ01 displayed colonization in the rhizosphere and endosphere in the roots of Arabidopsis. In conclusion, the newly isolated Enterobacter sp. EJ01 is a likely PGPR and alleviates salt stress in host plants through multiple mechanisms, including the rapid up-regulation of conserved plant salt stress responsive signaling pathways.
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Affiliation(s)
- Kangmin Kim
- Division of Biotechnology, College of Environmental and Bioresource Sciences
| | - Ye-Jin Jang
- Division of Biotechnology, College of Environmental and Bioresource Sciences
| | - Sang-Myeong Lee
- Division of Biotechnology, College of Environmental and Bioresource Sciences
- Advanced Institute of Environment and Bioscience, Chonbuk National University, Iksan 570-752, Korea
| | - Byung-Taek Oh
- Division of Biotechnology, College of Environmental and Bioresource Sciences
- Advanced Institute of Environment and Bioscience, Chonbuk National University, Iksan 570-752, Korea
| | - Jong-Chan Chae
- Division of Biotechnology, College of Environmental and Bioresource Sciences
- Advanced Institute of Environment and Bioscience, Chonbuk National University, Iksan 570-752, Korea
| | - Kui-Jae Lee
- Division of Biotechnology, College of Environmental and Bioresource Sciences
- Advanced Institute of Environment and Bioscience, Chonbuk National University, Iksan 570-752, Korea
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605
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Spaepen S, Bossuyt S, Engelen K, Marchal K, Vanderleyden J. Phenotypical and molecular responses of Arabidopsis thaliana roots as a result of inoculation with the auxin-producing bacterium Azospirillum brasilense. THE NEW PHYTOLOGIST 2014; 201:850-861. [PMID: 24219779 DOI: 10.1111/nph.12590] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/24/2013] [Indexed: 05/18/2023]
Abstract
The auxin-producing bacterium Azospirillum brasilense Sp245 can promote the growth of several plant species. The model plant Arabidopsis thaliana was chosen as host plant to gain an insight into the molecular mechanisms that govern this interaction. The determination of differential gene expression in Arabidopsis roots after inoculation with either A. brasilense wild-type or an auxin biosynthesis mutant was achieved by microarray analysis. Arabidopsis thaliana inoculation with A. brasilense wild-type increases the number of lateral roots and root hairs, and elevates the internal auxin concentration in the plant. The A. thaliana root transcriptome undergoes extensive changes on A. brasilense inoculation, and the effects are more pronounced at later time points. The wild-type bacterial strain induces changes in hormone- and defense-related genes, as well as in plant cell wall-related genes. The A. brasilense mutant, however, does not elicit these transcriptional changes to the same extent. There are qualitative and quantitative differences between A. thaliana responses to the wild-type A. brasilense strain and the auxin biosynthesis mutant strain, based on both phenotypic and transcriptomic data. This illustrates the major role played by auxin in the Azospirillum-Arabidopsis interaction, and possibly also in other bacterium-plant interactions.
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Affiliation(s)
- Stijn Spaepen
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
| | - Stijn Bossuyt
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
| | - Kristof Engelen
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
- Fondazione Edmund Mach, Research and Innovation Centre, Via E. Mach, 1, 38010, San Michele all'Adige, Trento, Italy
| | - Kathleen Marchal
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Gent, Belgium
| | - Jos Vanderleyden
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001, Heverlee, Belgium
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606
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Gumiere T, Ribeiro CM, Vasconcellos RLF, Cardoso EJBN. Indole-3-acetic acid producing root-associated bacteria on growth of Brazil Pine (Araucaria angustifolia) and Slash Pine (Pinus elliottii). Antonie van Leeuwenhoek 2014; 105:663-9. [PMID: 24481491 DOI: 10.1007/s10482-014-0120-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Accepted: 01/17/2014] [Indexed: 12/21/2022]
Abstract
Araucaria forests in Brazil today correspond to only 0.7 % of the original 200 km(2) of natural forest that covered a great part of the southern and southeastern area of the Atlantic Forest and, although Araucaria angustifolia is an endangered species, illegal exploitation is still going on. As an alternative to the use of hardwoods, Pinus elliottii presents rapid growth and high tolerance to climatic stress and low soil fertility or degraded areas. Thus, the objective of this study was to evaluate the effect of IAA-producing bacteria on the development of A. angustifolia and P. elliottii. We used five bacterial strains previously isolated from the rhizosphere of A. angustifolia, which produce quantities of IAA ranging from 3 to 126 μg mL(-1). Microbiolized seeds were sown in a new gnotobiotic system developed for this work, that allowed the quantification of the plant hormone IAA produced by bacteria, and the evaluation of its effect on seedling development. Also, it was shown that P. elliottii roots were almost as satisfactory as hosts for these IAA producers as A. angustifolia, while different magnitudes of mass increases were found for each species. Thus, we suggest that these microbial groups can be helpful for the development and reestablishment of already degraded forests and that PGPR isolated from Araucaria rhizosphere have the potential to be beneficial in seedling production of P. elliottii. Another finding is that our newly developed gnotobiotic system is highly satisfactory for the evaluation of this effect.
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Affiliation(s)
- Thiago Gumiere
- Soil Microbiology Laboratory, Department of Soil Science, Luiz de Queiroz College of Agriculture, University of São Paulo, ESALQ/USP, Av. Pádua Dias, 11, CP 09, Piracicaba, São Paulo, 13418-900, Brazil,
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607
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Complete Genome Sequence of the Sugar Cane Endophyte Pseudomonas aurantiaca PB-St2, a Disease-Suppressive Bacterium with Antifungal Activity toward the Plant Pathogen Colletotrichum falcatum. GENOME ANNOUNCEMENTS 2014; 2:2/1/e01108-13. [PMID: 24459254 PMCID: PMC3900886 DOI: 10.1128/genomea.01108-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The endophytic bacterium Pseudomonas aurantiaca PB-St2 exhibits antifungal activity and represents a biocontrol agent to suppress red rot disease of sugar cane. Here, we report the completely sequenced 6.6-Mb genome of P. aurantiaca PB-St2. The sequence contains a repertoire of biosynthetic genes for secondary metabolites that putatively contribute to its antagonistic activity and its plant-microbe interactions.
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608
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Duca D, Lorv J, Patten CL, Rose D, Glick BR. Indole-3-acetic acid in plant-microbe interactions. Antonie van Leeuwenhoek 2014; 106:85-125. [PMID: 24445491 DOI: 10.1007/s10482-013-0095-y] [Citation(s) in RCA: 325] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 12/07/2013] [Indexed: 01/04/2023]
Abstract
Indole-3-acetic acid (IAA) is an important phytohormone with the capacity to control plant development in both beneficial and deleterious ways. The ability to synthesize IAA is an attribute that many bacteria including both plant growth-promoters and phytopathogens possess. There are three main pathways through which IAA is synthesized; the indole-3-pyruvic acid, indole-3-acetamide and indole-3-acetonitrile pathways. This chapter reviews the factors that effect the production of this phytohormone, the role of IAA in bacterial physiology and in plant-microbe interactions including phytostimulation and phytopathogenesis.
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Affiliation(s)
- Daiana Duca
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada,
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609
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Limtong S, Kaewwichian R, Yongmanitchai W, Kawasaki H. Diversity of culturable yeasts in phylloplane of sugarcane in Thailand and their capability to produce indole-3-acetic acid. World J Microbiol Biotechnol 2014; 30:1785-96. [PMID: 24442819 DOI: 10.1007/s11274-014-1602-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Accepted: 01/12/2014] [Indexed: 10/25/2022]
Abstract
Yeasts were isolated by the enrichment technique from the phylloplane of 94 samples of sugarcane leaf collected from seven provinces in Thailand. All sugarcane leaf samples contained yeasts and 158 yeast strains were obtained. On the basis of the D1/D2 domain of the large subunit rRNA gene sequence analysis, 144 strains were identified to 24 known species in 14 genera belonging to the Ascomycota viz. Candida akabanensis, Candida dendronema, Candida mesorugosa, Candida michaelii, Candida nivariensis, Candida rugosa, Candida orthopsilosis, Candida quercitrusa, Candida tropicalis, Candida xylopsoci, Cyberlindnera fabianii, Cyberlindnera rhodanensis, Debaryomyces nepalensis, Hannaella aff. coprosmaensis, Hanseniaspora guilliermondii, Kluyveromyces marxianus, Lachancea thermotolerans, Lodderomyces elongisporus, Metschnikowia koreensis, Meyerozyma caribbica, Millerozyma koratensis, Pichia kudriavzevii, Torulaspora delbrueckii and Wickerhamomyces edaphicus, and 12 species in six genera of the Basidiomycota viz . Cryptococcus flavescens, Cryptococcus laurentii, Cryptococcus rajasthanensis, Kwoniella heveanensis, Rhodosporidium fluviale, Rhodosporidium paludigenum, Rhodotorula mucilaginosa, Rhodotorula sesimbrana, Rhodotorula taiwanensis, Sporidiobolus ruineniae, Sporobolomyces carnicolor and Sporobolomyces nylandii. Seven strains were identical or similar to four undescribed species. Another seven strains represented four novels species in the genus Metschnikowia, Nakazawaea, Wickerhamomyces and Yamadazyma. The results revealed 69 % of the isolated strains were ascomycete yeasts and 31 % were basidiomycete yeast. The most prevalent species was M. caribbica with a 23 % frequency of occurrence followed by Rh. taiwanensis (11 %) and C. tropicalis (10 %). All strains were assessed for indole-3-acetic acid (IAA) producing capability showing that 69 strains had the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 1 g/L L-tryptophan. The highest IAA concentration of 565.1 mg/L was produced by R. fluviale DMKU-RK253.
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Affiliation(s)
- Savitree Limtong
- Department of Microbiology, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand,
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610
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Hao X, Taghavi S, Xie P, Orbach MJ, Alwathnani HA, Rensing C, Wei G. Phytoremediation of heavy and transition metals aided by legume-rhizobia symbiosis. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2014; 16:179-202. [PMID: 24912209 DOI: 10.1080/15226514.2013.773273] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Legumes are important for nitrogen cycling in the environment and agriculture due to the ability of nitrogen fixation by rhizobia. In this review, we introduce an important and potential role of legume-rhizobia symbiosis in aiding phytoremediation of some metal contaminated soils as various legumes have been found to be the dominant plant species in metal contaminated areas. Resistant rhizobia used for phytoremediation could act on metals directly by chelation, precipitation, transformation, biosorption and accumulation. Moreover, the plant growth promoting (PGP) traits of rhizobia including nitrogen fixation, phosphorus solubilization, phytohormone synthesis, siderophore release, and production of ACC deaminase and the volatile compounds of acetoin and 2, 3-butanediol may facilitate legume growth while lessening metal toxicity. The benefits of using legumes inoculated with naturally resistant rhizobia or recombinant rhizobia with enhanced resistance, as well as co-inoculation with other plant growth promoting bacteria (PGPB) are discussed. However, the legume-rhizobia symbiosis appears to be sensitive to metals, and the effect of metal toxicity on the interaction between legumes and rhizobia is not clear. Therefore, to obtain the maximum benefits from legumes assisted by rhizobia for phytoremediation of metals, it is critical to have a good understanding of interactions between PGP traits, the symbiotic plant-rhizobia relationship and metals.
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611
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Fatnassi IC, Chiboub M, Saadani O, Jebara M, Jebara SH. Phytostabilization of moderate copper contaminated soils using co-inoculation ofVicia fabawith plant growth promoting bacteria. J Basic Microbiol 2013; 55:303-11. [DOI: 10.1002/jobm.201300323] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 11/10/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Imen Challougui Fatnassi
- Laboratory of Legumes, University Tunis El Manar; Centre of Biotechnology of Borj Cedria; Hammam Lif Tunisia
| | - Manel Chiboub
- Laboratory of Legumes, University Tunis El Manar; Centre of Biotechnology of Borj Cedria; Hammam Lif Tunisia
| | - Omar Saadani
- Laboratory of Legumes, University Tunis El Manar; Centre of Biotechnology of Borj Cedria; Hammam Lif Tunisia
| | - Moez Jebara
- Laboratory of Legumes, University Tunis El Manar; Centre of Biotechnology of Borj Cedria; Hammam Lif Tunisia
| | - Salwa Harzalli Jebara
- Laboratory of Legumes, University Tunis El Manar; Centre of Biotechnology of Borj Cedria; Hammam Lif Tunisia
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612
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Drogue B, Sanguin H, Borland S, Prigent-Combaret C, Wisniewski-Dyé F. Genome wide profiling of Azospirillum lipoferum 4B gene expression during interaction with rice roots. FEMS Microbiol Ecol 2013; 87:543-55. [PMID: 24283406 DOI: 10.1111/1574-6941.12244] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/18/2013] [Accepted: 10/31/2013] [Indexed: 01/02/2023] Open
Abstract
Azospirillum-plant cooperation has been mainly studied from an agronomic point of view leading to a wide description of mechanisms implicated in plant growth-promoting effects. However, little is known about genetic determinants implicated in bacterial adaptation to the host plant during the transition from free-living to root-associated lifestyles. This study aims at characterizing global gene expression of Azospirillum lipoferum 4B following a 7-day-old interaction with two cultivars of Oryza sativa L. japonica (cv. Cigalon from which it was originally isolated, and cv. Nipponbare). The analysis was done on a whole genome expression array with RNA samples obtained from planktonic cells, sessile cells, and root-adhering cells. Root-associated Azospirillum cells grow in an active sessile-like state and gene expression is tightly adjusted to the host plant. Adaptation to rice seems to involve genes related to reactive oxygen species (ROS) detoxification and multidrug efflux, as well as complex regulatory networks. As revealed by the induction of genes encoding transposases, interaction with root may drive bacterial genome rearrangements. Several genes related to ABC transporters and ROS detoxification display cultivar-specific expression profiles, suggesting host specific adaptation and raising the question of A. lipoferum 4B/rice cv. Cigalon co-adaptation.
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Affiliation(s)
- Benoît Drogue
- UMR5557 CNRS, Ecologie Microbienne, Université de Lyon, Villeurbanne, France
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613
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Repar J, Šućurović S, Zahradka K, Zahradka D, Ćurković-Perica M. Stress resistance of Escherichia coli and Bacillus subtilis is modulated by auxins. Can J Microbiol 2013; 59:766-70. [PMID: 24206360 DOI: 10.1139/cjm-2013-0266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two bacterial species, Gram-negative Escherichia coli and Gram-positive Bacillus subtilis, were exposed to different auxins to examine possible effects of these substances on bacterial stress tolerance. Bacterial resistance to UV irradiation, heat shock, and streptomycin was assessed with and without previous exposure to the following auxins: indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and 1-naphthalene acetic acid (NAA). Escherichia coli and B. subtilis cultures pretreated with any of the 3 auxins survived UV irradiation better than the untreated cultures. Also, B. subtilis cultures pretreated with IBA or NAA survived prolonged heat exposure better than the untreated cultures, while IAA pretreatment had no effect on heat shock survival. In contrast, auxin pretreatment rendered E. coli more sensitive to heat shock. Escherichia coli cultures pretreated with auxins were also more sensitive to streptomycin, while auxin pretreatment had no effect on sensitivity of B. subtilis to streptomycin. These results show that auxins may either enhance or reduce bacterial tolerance to different stressors, depending on the bacterial species and the type and level of the stress. Auxins usually had similar effects on the same bacterial species in cases when the same type and level of stress were applied.
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Affiliation(s)
- J Repar
- a Department of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
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614
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de Oliveira-Longatti SM, Marra LM, Lima Soares B, Bomfeti CA, da Silva K, Avelar Ferreira PA, de Souza Moreira FM. Bacteria isolated from soils of the western Amazon and from rehabilitated bauxite-mining areas have potential as plant growth promoters. World J Microbiol Biotechnol 2013; 30:1239-50. [PMID: 24197786 DOI: 10.1007/s11274-013-1547-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 10/29/2013] [Indexed: 12/01/2022]
Abstract
Several processes that promote plant growth were investigated in endophytic and symbiotic bacteria isolated from cowpea and siratro nodules and also in bacterial strains recommended for the inoculation of cowpea beans. The processes verified in 31 strains were: antagonism against phytopathogenic fungi, free-living biological nitrogen fixation, solubilization of insoluble phosphates and indole acetic acid (IAA) production. The resistance to antibiotics was also assessed. Sequencing of the partial 16S rRNA gene was performed and the strains were identified as belonging to different genera. Eight strains, including some identified as Burkholderia fungorum, fixed nitrogen in the free-living state. Eighteen strains exhibited potential to solubilize calcium phosphate, and 13 strains could solubilize aluminum phosphate. High levels of IAA production were recorded with L-tryptophan addition for the strain UFLA04-321 (42.3 μg mL⁻¹). Strains highly efficient in symbiosis with cowpea bean, including strains already approved as inoculants showed the ability to perform other processes that promote plant growth. Besides, these strains exhibited resistance to several antibiotics. The ability of the nitrogen-fixing bacteria to perform other processes and their adaptation to environmental conditions add value to these strains, which could lead to improved inoculants for plant growth and environmental quality.
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Affiliation(s)
- Silvia Maria de Oliveira-Longatti
- Postgraduate Program of Agricultural Microbiology, Department of Biology, Federal University of Lavras, P.O 3037, Lavras, MG, 37200-000, Brazil,
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615
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Lakshmanan V, Bais HP. Factors other than root secreted malic acid that contributes toward Bacillus subtilis FB17 colonization on Arabidopsis roots. PLANT SIGNALING & BEHAVIOR 2013; 8:e27277. [PMID: 24310121 PMCID: PMC4092310 DOI: 10.4161/psb.27277] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The plant growth promoting rhizobacterium (PGPR) Bacillus subtilis FB17 (hereafter FB17) induces resistance against broad pathogen including Pseudomonas syringae pv tomato (PstDC3000). The extent of plant protection by FB17 depends on establishment of root colonization followed by biofilm formation. The general convention dictates that beneficial rhizobacterium may suppress the root innate immune system to establish a robust colonization. However, it is still not well understood which genetic targets FB17 affects in plants to facilitate a symbiotic association. Our recent study, involving whole transcriptome analysis of Arabdiopsis thaliana roots treated with FB17 post 24 h of treatment showed totally 279 genes that were significantly up- or/ downregulated. Further, we found that the mutants for upregulated and downregulated genes post-FB17 colonization showed a differential phenotype for FB17 root colonization. Interestingly, plants mutated in the FB17-responsive genes showed increased Aluminum activated malate transporter (ALMT1) expression under foliar pathogen PstDC3000, infections, indicating the independent functionality of ALMT1 for bacterial recruitment. Taken together this, present study suggests that the establishment of interaction between the plant host and PGPR is a complex phenomenon which is regulated by multiple genetic components.
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Affiliation(s)
- Venkatachalam Lakshmanan
- Department of Plant and Soil Sciences; University of Delaware; Newark, DE USA
- Delaware Biotechnology Institute; Newark, DE USA
| | - Harsh P Bais
- Department of Plant and Soil Sciences; University of Delaware; Newark, DE USA
- Delaware Biotechnology Institute; Newark, DE USA
- Correspondence to: Harsh P Bais,
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616
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Aserse AA, Räsänen LA, Aseffa F, Hailemariam A, Lindström K. Diversity of sporadic symbionts and nonsymbiotic endophytic bacteria isolated from nodules of woody, shrub, and food legumes in Ethiopia. Appl Microbiol Biotechnol 2013; 97:10117-34. [PMID: 24196581 DOI: 10.1007/s00253-013-5248-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/17/2013] [Accepted: 08/21/2013] [Indexed: 10/26/2022]
Abstract
Fifty-five bacterial isolates were obtained from surface-sterilized nodules of woody and shrub legumes growing in Ethiopia: Crotalaria spp., Indigofera spp., and Erythrina brucei, and the food legumes soybean and common bean. Based on partial 16S rRNA gene sequence analysis, the majority of the isolates were identified as Gram-negative bacteria belonging to the genera Achromobacter, Agrobacterium, Burkholderia, Cronobacter, Enterobacter, Mesorhizobium, Novosphingobium, Pantoea, Pseudomonas, Rahnella, Rhizobium, Serratia, and Variovorax. Seven isolates were Gram-positive bacteria belonging to the genera Bacillus, Paenibacillus, Planomicrobium, and Rhodococcus. Amplified fragment length polymorphism (AFLP) fingerprinting showed that each strain was genetically distinct. According to phylogenetic analysis of recA, glnII, rpoB, and 16S rRNA gene sequences, Rhizobium, Mesorhizobium, and Agrobacterium were further classified into six different genospecies: Agrobacterium spp., Agrobacterium radiobacter, Rhizobium sp., Rhizobium phaseoli, Mesorhizobium sp., and putative new Rhizobium species. The strains from R. phaseoli, Rhizobium sp. IAR30, and Mesorhizobium sp. ERR6 induced nodules on their host plants. The other strains did not form nodules on their original host. Nine endophytic bacterial strains representing seven genera, Agrobacterium, Burkholderia, Paenibacillus, Pantoea, Pseudomonas, Rhizobium, and Serratia, were found to colonize nodules of Crotalaria incana and common bean on co-inoculation with symbiotic rhizobia. Four endophytic Rhizobium and two Agrobacterium strains had identical nifH gene sequences with symbiotic Rhizobium strains, suggesting horizontal gene transfer. Most symbiotic and nonsymbiotic endophytic bacteria showed plant growth-promoting properties in vitro, which indicate their potential role in the promotion of plant growth when colonizing plant roots and the rhizosphere.
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Affiliation(s)
- Aregu Amsalu Aserse
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, P.O. Box 56, 00014, Finland,
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617
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Pérez-Montaño F, Alías-Villegas C, Bellogín RA, del Cerro P, Espuny MR, Jiménez-Guerrero I, López-Baena FJ, Ollero FJ, Cubo T. Plant growth promotion in cereal and leguminous agricultural important plants: from microorganism capacities to crop production. Microbiol Res 2013; 169:325-36. [PMID: 24144612 DOI: 10.1016/j.micres.2013.09.011] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/20/2013] [Accepted: 09/21/2013] [Indexed: 10/26/2022]
Abstract
Plant growth-promoting rhizobacteria (PGPR) are free-living bacteria which actively colonize plant roots, exerting beneficial effects on plant development. The PGPR may (i) promote the plant growth either by using their own metabolism (solubilizing phosphates, producing hormones or fixing nitrogen) or directly affecting the plant metabolism (increasing the uptake of water and minerals), enhancing root development, increasing the enzymatic activity of the plant or "helping" other beneficial microorganisms to enhance their action on the plants; (ii) or may promote the plant growth by suppressing plant pathogens. These abilities are of great agriculture importance in terms of improving soil fertility and crop yield, thus reducing the negative impact of chemical fertilizers on the environment. The progress in the last decade in using PGPR in a variety of plants (maize, rice, wheat, soybean and bean) along with their mechanism of action are summarized and discussed here.
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Affiliation(s)
- F Pérez-Montaño
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - C Alías-Villegas
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - R A Bellogín
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - P del Cerro
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - M R Espuny
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - I Jiménez-Guerrero
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - F J López-Baena
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - F J Ollero
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain
| | - T Cubo
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012 Sevilla, Spain.
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618
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Hoffman MT, Gunatilaka MK, Wijeratne K, Gunatilaka L, Arnold AE. Endohyphal bacterium enhances production of indole-3-acetic acid by a foliar fungal endophyte. PLoS One 2013; 8:e73132. [PMID: 24086270 PMCID: PMC3782478 DOI: 10.1371/journal.pone.0073132] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 07/23/2013] [Indexed: 11/19/2022] Open
Abstract
Numerous plant pathogens, rhizosphere symbionts, and endophytic bacteria and yeasts produce the important phytohormone indole-3-acetic acid (IAA), often with profound effects on host plants. However, to date IAA production has not been documented among foliar endophytes -- the diverse guild of primarily filamentous Ascomycota that live within healthy, above-ground tissues of all plant species studied thus far. Recently bacteria that live within hyphae of endophytes (endohyphal bacteria) have been detected, but their effects have not been studied previously. Here we show not only that IAA is produced in vitro by a foliar endophyte (here identified as Pestalotiopsis aff. neglecta, Xylariales), but that IAA production is enhanced significantly when the endophyte hosts an endohyphal bacterium (here identified as Luteibacter sp., Xanthomonadales). Both the endophyte and the endophyte/bacterium complex appear to rely on an L-tryptophan dependent pathway for IAA synthesis. The bacterium can be isolated from the fungus when the symbiotic complex is cultivated at 36°C. In pure culture the bacterium does not produce IAA. Culture filtrate from the endophyte-bacterium complex significantly enhances growth of tomato in vitro relative to controls and to filtrate from the endophyte alone. Together these results speak to a facultative symbiosis between an endophyte and endohyphal bacterium that strongly influences IAA production, providing a new framework in which to explore endophyte-plant interactions.
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Affiliation(s)
- Michele T. Hoffman
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Malkanthi K. Gunatilaka
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
| | - Kithsiri Wijeratne
- Southwest Center for Natural Products Research and Commercialization, School of Natural Resources and the Environment, Tucson, Arizona, United States of America
| | - Leslie Gunatilaka
- Southwest Center for Natural Products Research and Commercialization, School of Natural Resources and the Environment, Tucson, Arizona, United States of America
| | - A. Elizabeth Arnold
- School of Plant Sciences, The University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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619
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Gopalakrishnan S, Vadlamudi S, Bandikinda P, Sathya A, Vijayabharathi R, Rupela O, Kudapa H, Katta K, Varshney RK. Evaluation of Streptomyces strains isolated from herbal vermicompost for their plant growth-promotion traits in rice. Microbiol Res 2013; 169:40-8. [PMID: 24113511 DOI: 10.1016/j.micres.2013.09.008] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 09/12/2013] [Accepted: 09/14/2013] [Indexed: 10/26/2022]
Abstract
Six actinomycetes, CAI-13, CAI-85, CAI-93, CAI-140, CAI-155 and KAI-180, isolated from six different herbal vermi-composts were characterized for in vitro plant growth-promoting (PGP) properties and further evaluated in the field for PGP activity in rice. Of the six actinomycetes, CAI-13, CAI-85, CAI-93, CAI-140 and CAI-155 produced siderophores; CAI-13, CAI-93, CAI-155 and KAI-180 produced chitinase; CAI-13, CAI-140, CAI-155 and KAI-180 produced lipase; CAI-13, CAI-93, CAI-155 and KAI-180 produced protease; and CAI-13, CAI-85, CAI-140 and CAI-155 produced ß-1-3-glucanase whereas all the six actinomycetes produced cellulase, hydrocyanic acid and indole acetic acid (IAA). The actinomycetes were able to grow in NaCl concentrations of up to 8%, at pH values between 7 and 11, temperatures between 20 and 40 °C and compatible with fungicide bavistin at field application levels. In the rice field, the actinomycetes significantly enhanced tiller numbers, panicle numbers, filled grain numbers and weight, stover yield, grain yield, total dry matter, root length, volume and dry weight over the un-inoculated control. In the rhizosphere, the actinomycetes also significantly enhanced total nitrogen, available phosphorous, % organic carbon, microbial biomass carbon and nitrogen and dehydrogenase activity over the un-inoculated control. Sequences of 16S rDNA gene of the actinomycetes matched with different Streptomyces species in BLAST analysis. Of the six actinomycetes, CAI-85 and CAI-93 were found superior over other actinomycetes in terms of PGP properties, root development and crop productivity. qRT-PCR analysis on selected plant growth promoting genes of actinomycetes revealed the up-regulation of IAA genes only in CAI-85 and CAI-93.
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Affiliation(s)
- Subramaniam Gopalakrishnan
- International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Andhra Pradesh, India.
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620
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Vacheron J, Desbrosses G, Bouffaud ML, Touraine B, Moënne-Loccoz Y, Muller D, Legendre L, Wisniewski-Dyé F, Prigent-Combaret C. Plant growth-promoting rhizobacteria and root system functioning. FRONTIERS IN PLANT SCIENCE 2013; 4:356. [PMID: 24062756 PMCID: PMC3775148 DOI: 10.3389/fpls.2013.00356] [Citation(s) in RCA: 511] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 08/23/2013] [Indexed: 05/18/2023]
Abstract
The rhizosphere supports the development and activity of a huge and diversified microbial community, including microorganisms capable to promote plant growth. Among the latter, plant growth-promoting rhizobacteria (PGPR) colonize roots of monocots and dicots, and enhance plant growth by direct and indirect mechanisms. Modification of root system architecture by PGPR implicates the production of phytohormones and other signals that lead, mostly, to enhanced lateral root branching and development of root hairs. PGPR also modify root functioning, improve plant nutrition and influence the physiology of the whole plant. Recent results provided first clues as to how PGPR signals could trigger these plant responses. Whether local and/or systemic, the plant molecular pathways involved remain often unknown. From an ecological point of view, it emerged that PGPR form coherent functional groups, whose rhizosphere ecology is influenced by a myriad of abiotic and biotic factors in natural and agricultural soils, and these factors can in turn modulate PGPR effects on roots. In this paper, we address novel knowledge and gaps on PGPR modes of action and signals, and highlight recent progress on the links between plant morphological and physiological effects induced by PGPR. We also show the importance of taking into account the size, diversity, and gene expression patterns of PGPR assemblages in the rhizosphere to better understand their impact on plant growth and functioning. Integrating mechanistic and ecological knowledge on PGPR populations in soil will be a prerequisite to develop novel management strategies for sustainable agriculture.
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Affiliation(s)
- Jordan Vacheron
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Guilhem Desbrosses
- Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR 113, Université Montpellier 2/Institut de Recherche Pour le Développement/Centre de Coopération Internationale en Recherche Agronomique pour le Développement/SupAgro/Institut National de la Recherche AgronomiqueMontpellier, France
| | - Marie-Lara Bouffaud
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
- Institut National de la Recherche Agronomique, UMR 1347, Agroécologie, Interactions Plantes-MicroorganismesDijon, France
| | - Bruno Touraine
- Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR 113, Université Montpellier 2/Institut de Recherche Pour le Développement/Centre de Coopération Internationale en Recherche Agronomique pour le Développement/SupAgro/Institut National de la Recherche AgronomiqueMontpellier, France
| | - Yvan Moënne-Loccoz
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Daniel Muller
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Laurent Legendre
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Florence Wisniewski-Dyé
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
| | - Claire Prigent-Combaret
- Université de LyonLyon, France
- Université Claude Bernard Lyon 1Villeurbanne, France
- Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1Villeurbanne, France
- *Correspondence: Claire Prigent-Combaret, Centre National de la Recherche Scientifique, UMR 5557, Ecologie Microbienne, Université Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France e-mail:
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621
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Panijel M, Chalupowicz L, Sessa G, Manulis-Sasson S, Barash I. Global regulatory networks control the hrp regulon of the gall-forming bacterium Pantoea agglomerans pv. gypsophilae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1031-1043. [PMID: 23745675 DOI: 10.1094/mpmi-04-13-0097-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Gall formation by Pantoea agglomerans pv. gypsophilae is dependent on the hypersensitive response and pathogenicity (hrp) system. Previous studies demonstrated that PagR and PagI, regulators of the quorum-sensing system, induce expression of the hrp regulatory cascade (i.e., hrpXY, hrpS, and hrpL) that activates the HrpL regulon. Here, we isolated the genes of the Gac/Rsm global regulatory pathway (i.e., gacS, gacA, rsmB, and csrD) and of the post-transcriptional regulator rsmA. Our results demonstrate that PagR and PagI also upregulate expression of the Gac/Rsm pathway. PagR acts as a transcriptional activator of each of the hrp regulatory genes and gacA in a N-butanoyl-L-homoserine lactone-dependent manner as shown by gel shift experiments. Mutants of the Gac/Rsm genes or overexpression of rsmA significantly reduced Pantoea agglomerans virulence and colonization of gypsophila. Overexpression of rsmB sRNA abolished gall formation, colonization, and hypersensitive reaction on nonhost plants and prevented transcription of the hrp regulatory cascade, indicating a lack of functional type III secretion system. Expression of rsmB sRNA in the background of the csrD null mutant suggests that CsrD may act as a safeguard for preventing excessive production of rsmB sRNA. Results presented indicate that the hrp regulatory cascade is controlled directly by PagR and indirectly by RsmA, whereas deficiency in RsmA activity is epistatic to PagR induction.
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Affiliation(s)
- Mary Panijel
- Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv, Israel
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622
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Fiester SE, Actis LA. Stress responses in the opportunistic pathogen Acinetobacter baumannii. Future Microbiol 2013; 8:353-65. [PMID: 23464372 DOI: 10.2217/fmb.12.150] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Acinetobacter baumannii causes a wide range of severe infections among compromised and injured patients worldwide. The relevance of these infections are, in part, due to the ability of this pathogen to sense and react to environmental and host stress signals, allowing it to persist and disseminate in medical settings and the human host. This review summarizes current knowledge on the roles that environmental and cellular stressors play in the ability of A. baumannii to resist nutrient deprivation, oxidative and nitrosative injury, and even the presence of the commonly used antiseptic ethanol, which could serve as a nutrient- and virulence-enhancing signal rather than just being a convenient disinfectant. Emerging experimental evidence supports the role of some of these responses in the pathogenesis of the infections A. baumannii causes in humans and its capacity to resist antibiotics and host response effectors.
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Affiliation(s)
- Steven E Fiester
- Department of Microbiology, Miami University, Oxford, OH 45056, USA
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623
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Baluška F, Mancuso S. Microorganism and filamentous fungi drive evolution of plant synapses. Front Cell Infect Microbiol 2013; 3:44. [PMID: 23967407 PMCID: PMC3744040 DOI: 10.3389/fcimb.2013.00044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 07/26/2013] [Indexed: 12/23/2022] Open
Abstract
In the course of plant evolution, there is an obvious trend toward an increased complexity of plant bodies, as well as an increased sophistication of plant behavior and communication. Phenotypic plasticity of plants is based on the polar auxin transport machinery that is directly linked with plant sensory systems impinging on plant behavior and adaptive responses. Similar to the emergence and evolution of eukaryotic cells, evolution of land plants was also shaped and driven by infective and symbiotic microorganisms. These microorganisms are the driving force behind the evolution of plant synapses and other neuronal aspects of higher plants; this is especially pronounced in the root apices. Plant synapses allow synaptic cell–cell communication and coordination in plants, as well as sensory-motor integration in root apices searching for water and mineral nutrition. These neuronal aspects of higher plants are closely linked with their unique ability to adapt to environmental changes.
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Affiliation(s)
- František Baluška
- IZMB, Department of Plant Cell Biology, University of Bonn Bonn, Germany.
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624
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Vidal-Quist JC, Rogers HJ, Mahenthiralingam E, Berry C. Bacillus thuringiensis colonises plant roots in a phylogeny-dependent manner. FEMS Microbiol Ecol 2013; 86:474-89. [PMID: 23822207 DOI: 10.1111/1574-6941.12175] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 06/24/2013] [Accepted: 06/24/2013] [Indexed: 11/30/2022] Open
Abstract
Although much is known about the pathology of Bacillus thuringiensis against invertebrates, current understanding of its natural ecology is limited. This study evaluated the biodiversity of B. thuringiensis in relation to its interaction with plants. Phylogenetic relationships between 44 reference and field-collected strains, determined using 16S rRNA and gyrB gene sequences, revealed a high degree of variability, similar to that found in databases. An Arabidopsis thaliana in vitro inoculation model was developed to screen the ability of B. thuringiensis to colonise roots. Significant colonisation differences up to 91-fold were observed between strains, and correlation between strain phylogeny and colonisation was found. The genetics and biochemistry of auxin production; presence of the gene encoding indole pyruvate decarboxylase; and the abilities of Bt strains to swarm, grow in rich/minimal media and affect root growth differed between the strains, but only auxin production correlated significantly with ability to colonise roots. Co-inoculation with Burkholderia phytofirmans PsJN or Pseudomonas fluorescens SBW25 produced no effect on B. thuringiensis colonisation levels, regardless of the co-inoculant. Similarly, root colonisation of A. thaliana mutants impaired in plant defences was not significantly higher compared with controls. This is the first systematic and phylogenetic evaluation of B. thuringiensis interaction with plants.
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625
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Functional characterization of the bacterial iac genes for degradation of the plant hormone indole-3-acetic acid. J Chem Ecol 2013; 39:942-51. [PMID: 23881445 DOI: 10.1007/s10886-013-0324-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 06/29/2013] [Accepted: 07/04/2013] [Indexed: 10/26/2022]
Abstract
Pseudomonas putida 1290 is a model organism for the study of bacterial degradation of the plant hormone indole-3-acetic acid (IAA). This property is encoded by the iac gene cluster. Insertional inactivation and/or deletion of individual iac genes and heterologous expression of the gene cluster in Escherichia coli were combined with mass spectrometry to demonstrate that iac-based degradation of IAA is likely to involve 2-hydroxy-IAA, 3-hydroxy-2-oxo-IAA, and catechol as intermediates. The first gene of the cluster, iacA encodes for the first step in the pathway, and also can convert indole to indoxyl to produce the blue pigment indigo. Transcriptional profiling of iac genes in P. putida 1290 revealed that they were induced in the presence of IAA. Based on results with an iacR knockout, we propose that this gene codes for a repressor of iacA expression and that exposure to IAA relieves this repression. Transformation of P. putida KT2440 (which cannot degrade IAA) with the iac gene cluster conferred the ability to grow on IAA as a sole source of carbon and energy, but not the ability to chemotaxi towards IAA. We could show such tactic response for P. putida 1290, thus representing the first demonstration of bacterial chemotaxis towards IAA. We discuss the ecological significance of our findings, and specifically the following question: under what circumstances do bacteria with the ability to degrade, recognize, and move towards IAA have a selective advantage?
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626
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Microbial inoculants and their impact on soil microbial communities: a review. BIOMED RESEARCH INTERNATIONAL 2013; 2013:863240. [PMID: 23957006 PMCID: PMC3728534 DOI: 10.1155/2013/863240] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 06/07/2013] [Accepted: 06/25/2013] [Indexed: 11/18/2022]
Abstract
The knowledge of the survival of inoculated fungal and bacterial strains in field and the effects of their release on the indigenous microbial communities has been of great interest since the practical use of selected natural or genetically modified microorganisms has been developed. Soil inoculation or seed bacterization may lead to changes in the structure of the indigenous microbial communities, which is important with regard to the safety of introduction of microbes into the environment. Many reports indicate that application of microbial inoculants can influence, at least temporarily, the resident microbial communities. However, the major concern remains regarding how the impact on taxonomic groups can be related to effects on functional capabilities of the soil microbial communities. These changes could be the result of direct effects resulting from trophic competitions and antagonistic/synergic interactions with the resident microbial populations, or indirect effects mediated by enhanced root growth and exudation. Combination of inoculants will not necessarily produce an additive or synergic effect, but rather a competitive process. The extent of the inoculation impact on the subsequent crops in relation to the buffering capacity of the plant-soil-biota is still not well documented and should be the focus of future research.
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627
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Hussain A, Hamayun M, Shah ST. Root colonization and phytostimulation by phytohormones producing entophytic Nostoc sp. AH-12. Curr Microbiol 2013; 67:624-30. [PMID: 23794014 DOI: 10.1007/s00284-013-0408-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 05/19/2013] [Indexed: 01/07/2023]
Abstract
Nostoc, a nitrogen-fixing cyanobacterium, has great potential to make symbiotic associations with a wide range of plants and benefit its hosts with nitrogen in the form of nitrates. It may also use phytohormones as a tool to promote plant growth. Phytohormones [cytokinin (Ck) and IAA] were determined in the culture of an endophytic Nostoc isolated from rice roots. The strain was able to accumulate as well as release phytohormones to the culture media. Optimum growth conditions for the production of zeatin and IAA were a temperature of 25 °C and a pH of 8.0. Time-dependent increase in the accumulation and release of phytohormones was recorded. To evaluate the impact of cytokinins, an ipt knockout mutant in the background of Nostoc was generated by homologous recombination method. A sharp decline (up to 80 %) in the zeatin content was observed in the culture of mutant strain Nostoc AHM-12. Association of the mutant and wild type strain with rice and wheat roots was studied under axenic conditions. The efficacy of Nostoc to colonize plant root was significantly reduced (P < 0.05) as a result of ipt inactivation as evident by low chlorophyll a concentration in the roots. In contrast to the mutant strain, wild type strain showed good association with the roots and enhanced several growth parameters, such as fresh weight, dry weight, shoot length, and root length of the crop plants. The study clearly demonstrated that Ck is a tool of endophytic Nostoc to colonize plant root and promote its growth.
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Affiliation(s)
- Anwar Hussain
- Department of Botany, University College of Science, Abdul Wali Khan University Mardan, Shankar Campus, Mardan, Pakistan,
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628
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Rapid Screening of Berseem Clover (Trifolium alexandrinum) Endophytic Bacteria for Rice Plant Seedlings Growth-Promoting Agents. ACTA ACUST UNITED AC 2013. [DOI: 10.1155/2013/371879] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A simple screening method to detect berseem clover (Trifolium alexandrinum) endophytic bacteria for rice plant growth-promoting agents on the basis of a root colonization bioassay and a plant growth promoting trait is characterized. Firstly, 200 isolates (80 endophytes and 120 rhizospheric isolates) isolated from berseem clover were inoculated as 10 mixtures of 20 strains each on two rice varieties under gnotobiotic conditions. Then, the reisolated endophytic strains from two rice varieties were characterized for plant growth promoting (PGP) traits. Secondly, the colonization and growth promoting effects of endophytic strains were compared in inoculated rice plantlets as single-strain inoculants. A significant relationship among indole-3-acetic acid (IAA) producing isolates, the size of root colonization, and plant growth was observed. Our results suggest that the ability of IAA production by the endophytic bacteria which may have a stimulatory effect on plant development may be the first plant growth promoting trait for screening bacteria isolated from clover plant for rice plant growth promoting agents. In addition, this study indicates that the selected bacterial isolates based on their IAA producing trait have the potential for PGP and more colonization of rice plant.
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629
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Cui F, Wu S, Sun W, Coaker G, Kunkel B, He P, Shan L. The Pseudomonas syringae type III effector AvrRpt2 promotes pathogen virulence via stimulating Arabidopsis auxin/indole acetic acid protein turnover. PLANT PHYSIOLOGY 2013; 162:1018-29. [PMID: 23632856 PMCID: PMC3668037 DOI: 10.1104/pp.113.219659] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 04/29/2013] [Indexed: 05/19/2023]
Abstract
To accomplish successful infection, pathogens deploy complex strategies to interfere with host defense systems and subvert host physiology to favor pathogen survival and multiplication. Modulation of plant auxin physiology and signaling is emerging as a common virulence strategy for phytobacteria to cause diseases. However, the underlying mechanisms remain largely elusive. We have previously shown that the Pseudomonas syringae type III effector AvrRpt2 alters Arabidopsis (Arabidopsis thaliana) auxin physiology. Here, we report that AvrRpt2 promotes auxin response by stimulating the turnover of auxin/indole acetic acid (Aux/IAA) proteins, the key negative regulators in auxin signaling. AvrRpt2 acts additively with auxin to stimulate Aux/IAA turnover, suggesting distinct, yet proteasome-dependent, mechanisms operated by AvrRpt2 and auxin to control Aux/IAA stability. Cysteine protease activity is required for AvrRpt2-stimulated auxin signaling and Aux/IAA degradation. Importantly, transgenic plants expressing the dominant axr2-1 mutation recalcitrant to AvrRpt2-mediated degradation ameliorated the virulence functions of AvrRpt2 but did not alter the avirulent function mediated by the corresponding RPS2 resistance protein. Thus, promoting auxin response via modulating the stability of the key transcription repressors Aux/IAA is a mechanism used by the bacterial type III effector AvrRpt2 to promote pathogenicity.
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630
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Marchi M, Boutin M, Gazengel K, Rispe C, Gauthier JP, Guillerm-Erckelboudt AY, Lebreton L, Barret M, Daval S, Sarniguet A. Genomic analysis of the biocontrol strain Pseudomonas fluorescens Pf29Arp with evidence of T3SS and T6SS gene expression on plant roots. ENVIRONMENTAL MICROBIOLOGY REPORTS 2013; 5:393-403. [PMID: 23754720 DOI: 10.1111/1758-2229.12048] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 02/21/2013] [Accepted: 02/23/2013] [Indexed: 05/05/2023]
Abstract
Several bacterial strains of the Pseudomonas genus provide plant growth stimulation, plant protection against pests or bioremediation. Among these bacteria, P. fluorescens Pf29Arp reduces the severity of take-all, a disease caused by the pathogenic fungus Gaeumannomyces graminis var. tritici (Ggt) on wheat roots. In this study, we obtained a draft genome of Pf29Arp and subsequent comparative genomic analyses have revealed that this bacterial strain is closely related to strains of the 'P. brassicacearum-like' subgroup including P. brassicacearum ssp. brassicacearum NFM421 and P. fluorescens F113. Despite an overall chromosomal organization similar to these strains, a number of features including antibiotic synthesis gene clusters from secondary metabolism are not found in the Pf29Arp genome. But Pf29Arp possesses different protein secretion systems including type III (T3SS) and type VI (T6SS) secretion systems. Pf29Arp is the first Pseudomonas sp. strain described with four T6SS clusters (cluster I, II, III and IV). In addition, some protein-coding genes involved in the assembly of these secretion systems are basally expressed during Pf29Arp colonization of healthy wheat roots and display different expression patterns on necrotized roots caused by Ggt. These data suggest a role of T3SS and T6SS in the Pf29Arp adaptation to different root environments.
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631
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Identification of two strains of Paenibacillus sp. as indole 3 acetic acid-producing rhizome-associated endophytic bacteria from Curcuma longa. 3 Biotech 2013; 3:219-224. [PMID: 28324371 PMCID: PMC3646110 DOI: 10.1007/s13205-012-0086-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 08/23/2012] [Indexed: 11/17/2022] Open
Abstract
Curcuma longa is well known for its use as spice and medicine. The remarkable feature of the plant is the presence of rhizome, which provides an interesting habitat for association by various groups of bacteria. Some of these associated endophytic bacteria can have growth-promoting effects. In the current study, two species of endophytic Paenibacillus has been identified from the rhizome as indole 3 acetic acid producers. These isolates can thus have potential growth-regulating effect in rhizomes.
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632
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Edmonds KE. Melatonin, But not Auxin, Affects Postnatal Reproductive Development in the Marsh Rice Rat (Oryzomys palustris). Zoolog Sci 2013; 30:439-45. [DOI: 10.2108/zsj.30.439] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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633
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tyrB-2 and phhC genes of Pseudomonas putida encode aromatic amino acid aminotransferase isozymes: evidence at the protein level. Amino Acids 2013; 45:351-8. [PMID: 23685963 PMCID: PMC3714555 DOI: 10.1007/s00726-013-1508-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 05/04/2013] [Indexed: 01/08/2023]
Abstract
Two Pseudomonas putida aminotransferases (ArAT I and ArAT II) that exhibit activity toward L-tryptophan were purified 104- and 395-fold using a six-stage purification procedure involving ammonium sulfate fractionation and chromatographic separation on phenyl-Sepharose, Sephadex G-100 superfine, DEAE-cellulose and Protein-Pack Q8 HR columns. Mass spectrometry analysis resulted in the identification of 27 and 20 % of the total ArAT I and ArAT II amino acid sequences. In addition, N-terminal sequence fragments of ArAT I and ArAT II were determined using the Edman degradation method. Based on the analyses performed, the studied proteins were identified as products of the tyrB-2 and phhC genes, and the presence of these genes in the investigated bacterial strain was confirmed using molecular biology methods. Extensive analysis of the substrate specificities of ArAT I and ArAT II revealed that both enzymes most efficiently catalyzed reactions involving aromatic amino acids and 2-oxoacids followed by dicarboxylic compounds. The best substrates for ArAT I and ArAT II were L-phenylalanine and phenylpyruvate. Based on these results, the studied proteins were classified as aromatic amino acid aminotransferase isozymes.
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634
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Bal HB, Das S, Dangar TK, Adhya TK. ACC deaminase and IAA producing growth promoting bacteria from the rhizosphere soil of tropical rice plants. J Basic Microbiol 2013; 53:972-84. [PMID: 23681643 DOI: 10.1002/jobm.201200445] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Accepted: 12/08/2012] [Indexed: 11/11/2022]
Abstract
Beneficial plant-associated bacteria play a key role in supporting and/or promoting plant growth and health. Plant growth promoting bacteria present in the rhizosphere of crop plants can directly affect plant metabolism or modulate phytohormone production or degradation. We isolated 355 bacteria from the rhizosphere of rice plants grown in the farmers' fields in the coastal rice field soil from five different locations of the Ganjam district of Odisha, India. Six bacteria producing both ACC deaminase (ranging from 603.94 to 1350.02 nmol α-ketobutyrate mg(-1) h(-1) ) and indole acetic acid (IAA; ranging from 10.54 to 37.65 μM ml(-1) ) in pure cultures were further identified using polyphasic taxonomy including BIOLOG((R)) , FAME analysis and the 16S rRNA gene sequencing. Phylogenetic analyses of the isolates resulted into five major clusters to include members of the genera Bacillus, Microbacterium, Methylophaga, Agromyces, and Paenibacillus. Seed inoculation of rice (cv. Naveen) by the six individual PGPR isolates had a considerable impact on different growth parameters including root elongation that was positively correlated with ACC deaminase activity and IAA production. The cultures also had other plant growth attributes including ammonia production and at least two isolates produced siderophores. Study indicates that presence of diverse rhizobacteria with effective growth-promoting traits, in the rice rhizosphere, may be exploited for a sustainable crop management under field conditions.
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Affiliation(s)
- Himadri Bhusan Bal
- Laboratory of Soil Microbiology, Division of Crop Production, Central Rice Research Institute, Cuttack, Odisha, India
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635
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Carbon catabolite repression-independent and pH-dependent production of indoles by Rubrivivax benzoatilyticus JA2. Curr Microbiol 2013; 67:399-405. [PMID: 23666086 DOI: 10.1007/s00284-013-0378-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
Abstract
Rubrivivax benzoatilyticus JA2 produces indole derivatives (indoles) from aniline, anthranilate or L-tryptophan. Glucose repressed indole production in R. benzoatilyticus JA2, while malate had no effect. Growth of R. benzoatilyticus JA2 on glucose resulted in decrease in culture pH (6.4) compared with malate (8.4). Growth of R. benzoatilyticus JA2 on sugar carbon sources decreased culture pH (6.4-6.6) and indole production. Further, culture pH of 6.4 repressed the indole production, and pH 8.4 promoted the production irrespective of carbon sources used for growth. Moreover, correlation between indole production and culture pH was observed, where acidic pH inhibited indole production, while alkaline pH promoted the production, suggesting the role of pH in indole production. Tryptophan-catabolizing enzyme activities are significantly high in malate-grown cultures (pH 8.4) compared with that of the glucose (pH 6.4)-grown cultures and corroborated well with indole production, indicating their role in indole production. These results confirm that indole production in R. benzoatilyticus JA2 is pH dependent rather than carbon catabolite repression.
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636
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Zúñiga A, Poupin MJ, Donoso R, Ledger T, Guiliani N, Gutiérrez RA, González B. Quorum sensing and indole-3-acetic acid degradation play a role in colonization and plant growth promotion of Arabidopsis thaliana by Burkholderia phytofirmans PsJN. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:546-53. [PMID: 23301615 DOI: 10.1094/mpmi-10-12-0241-r] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Although not fully understood, molecular communication in the rhizosphere plays an important role regulating traits involved in plant-bacteria association. Burkholderia phytofirmans PsJN is a well-known plant-growth-promoting bacterium, which establishes rhizospheric and endophytic colonization in different plants. A competent colonization is essential for plant-growth-promoting effects produced by bacteria. Using appropriate mutant strains of B. phytofirmans, we obtained evidence for the importance of N-acyl homoserine lactone-mediated (quorum sensing) cell-to-cell communication in efficient colonization of Arabidopsis thaliana plants and the establishment of a beneficial interaction. We also observed that bacterial degradation of the auxin indole-3-acetic acid (IAA) plays a key role in plant-growth-promoting traits and is necessary for efficient rhizosphere colonization. Wildtype B. phytofirmans but not the iacC mutant in IAA mineralization is able to restore promotion effects in roots of A. thaliana in the presence of exogenously added IAA, indicating the importance of this trait for promoting primary root length. Using a transgenic A. thaliana line with suppressed auxin signaling (miR393) and analyzing the expression of auxin receptors in wild-type inoculated plants, we provide evidence that auxin signaling in plants is necessary for the growth promotion effects produced by B. phytofirmans. The interplay between ethylene and auxin signaling was also confirmed by the response of the plant to a 1-aminocyclopropane-1-carboxylate deaminase bacterial mutant strain.
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Affiliation(s)
- Ana Zúñiga
- Universidad Adolfo Ibanez, Santiago, Chile
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637
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Abstract
Auxin plays important roles during the entire life span of a plant. This small organic acid influences cell division, cell elongation and cell differentiation, and has great impact on the final shape and function of cells and tissues in all higher plants. Auxin metabolism is not well understood but recent discoveries, reviewed here, have started to shed light on the processes that regulate the synthesis and degradation of this important plant hormone.
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Affiliation(s)
- Karin Ljung
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
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638
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Kechid M, Desbrosses G, Rokhsi W, Varoquaux F, Djekoun A, Touraine B. The NRT2.5 and NRT2.6 genes are involved in growth promotion of Arabidopsis by the plant growth-promoting rhizobacterium (PGPR) strain Phyllobacterium brassicacearum STM196. THE NEW PHYTOLOGIST 2013; 198:514-524. [PMID: 23398541 DOI: 10.1111/nph.12158] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 12/14/2012] [Indexed: 05/26/2023]
Abstract
The Phyllobacterium brassicacearum STM196 strain stimulates Arabidopsis thaliana growth and antagonizes high nitrate inhibition of lateral root development. A previous study identified two STM196-responsive genes, NRT2.5 and NRT2.6 (Mantelin et al., 2006, Planta 223: 591-603). We investigated the role of NRT2.5 and NRT2.6 in the plant response to STM196 using single and double Arabidopsis mutants. The single mutants were also crossed with an nrt2.1 mutant, lacking the major nitrate root transporter, to distinguish the effects of NRT2.5 and NRT2.6 from potential indirect effects of nitrate pools. The nrt2.5 and nrt2.6 mutations abolished the plant growth and root system architecture responses to STM196. The determination of nitrate content revealed that NRT2.5 and NRT2.6 do not play an important role in nitrate distribution between plant organs. Conversely, NRT2.5 and NRT2.6 appeared to play a role in the plant response independent of nitrate uptake. Using a nitrate reductase mutant, it was confirmed that the NRT2.5/NRT2.6-dependent plant signalling pathway is independent of nitrate-dependent regulation of root development. Our findings demonstrate that NRT2.5 and NRT2.6, which are preferentially expressed in leaves, play an essential role in plant growth promotion by the rhizospheric bacterium STM196.
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Affiliation(s)
- Maya Kechid
- Laboratory of Tropical and Mediterranean Symbioses (UMR113, Université Montpellier 2, Institut de Recherche pour le Développement, Cirad Montpellier SupAgro, Institut National de la Recherche Agronomique), Université Montpellier 2, CC002, Place E. Bataillon, F34095, Montpellier Cedex 5, France
- Genetic Biochemistry and Plant Biotechnology Laboratory (Département de Biologie Végétale-Ecologie, Faculté de Science de la nature et de la vie), Mentouri University, Route de Ain El Bey, 25000, Constantine, Algeria
| | - Guilhem Desbrosses
- Laboratory of Tropical and Mediterranean Symbioses (UMR113, Université Montpellier 2, Institut de Recherche pour le Développement, Cirad Montpellier SupAgro, Institut National de la Recherche Agronomique), Université Montpellier 2, CC002, Place E. Bataillon, F34095, Montpellier Cedex 5, France
| | - Wafaa Rokhsi
- Laboratory of Tropical and Mediterranean Symbioses (UMR113, Université Montpellier 2, Institut de Recherche pour le Développement, Cirad Montpellier SupAgro, Institut National de la Recherche Agronomique), Université Montpellier 2, CC002, Place E. Bataillon, F34095, Montpellier Cedex 5, France
| | - Fabrice Varoquaux
- Laboratory of Tropical and Mediterranean Symbioses (UMR113, Université Montpellier 2, Institut de Recherche pour le Développement, Cirad Montpellier SupAgro, Institut National de la Recherche Agronomique), Université Montpellier 2, CC002, Place E. Bataillon, F34095, Montpellier Cedex 5, France
| | - Abdelhamid Djekoun
- Genetic Biochemistry and Plant Biotechnology Laboratory (Département de Biologie Végétale-Ecologie, Faculté de Science de la nature et de la vie), Mentouri University, Route de Ain El Bey, 25000, Constantine, Algeria
| | - Bruno Touraine
- Laboratory of Tropical and Mediterranean Symbioses (UMR113, Université Montpellier 2, Institut de Recherche pour le Développement, Cirad Montpellier SupAgro, Institut National de la Recherche Agronomique), Université Montpellier 2, CC002, Place E. Bataillon, F34095, Montpellier Cedex 5, France
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639
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Kadyan S, Panghal M, Kumar S, Singh K, Yadav JP. Assessment of functional and genetic diversity of aerobic endospore forming Bacilli from rhizospheric soil of Phyllanthus amarus L. World J Microbiol Biotechnol 2013; 29:1597-610. [DOI: 10.1007/s11274-013-1323-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Accepted: 03/15/2013] [Indexed: 10/27/2022]
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640
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Indole-3-acetic acid production by endophytic Streptomyces sp. En-1 isolated from medicinal plants. Curr Microbiol 2013; 67:209-17. [PMID: 23512121 DOI: 10.1007/s00284-013-0348-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 02/26/2013] [Indexed: 01/28/2023]
Abstract
Plant-associated actinobacteria are rich sources of bioactive compounds including indole-derived molecules such as phytohormone indole-3-acetic acid (IAA). In view of few investigations concerning the biosynthesis of IAA by endophytic actinobacteria, this study evaluated the potential of IAA production in endophytic streptomycete isolates sourced from medicinal plant species Taxus chinensis and Artemisia annua. By HPLC analysis of IAA combined with molecular screening approach of iaaM, a genetic determinant of streptomycete IAA synthesis via indole-3-acetamide (IAM), our data showed the putative operation of IAM-mediated IAA biosynthesis in Streptomyces sp. En-1 endophytic to Taxus chinensis. Furthermore, using the co-cultivation system of model plant Arabidopsis thaliana and streptomycete, En-1 was found to be colonized intercellularly in the tissues of Arabidopsis, an alternative host, and the effects of endophytic En-1 inoculation on the model plant were also assayed. The phytostimulatory effects of En-1 inoculation suggest that IAA-producing Streptomyces sp. En-1 of endophytic origin could be a promising candidate for utilization in growth improvement of plants of economic and agricultural value.
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641
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Kulkarni GB, Nayak AS, Sajjan SS, Oblesha A, Karegoudar TB. Indole-3-acetic acid biosynthetic pathway and aromatic amino acid aminotransferase activities in Pantoea dispersa strain GPK. Lett Appl Microbiol 2013; 56:340-7. [PMID: 23448265 DOI: 10.1111/lam.12053] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 01/20/2013] [Accepted: 01/28/2013] [Indexed: 10/27/2022]
Abstract
This investigation deals with the production of IAA by a bacterial isolate Pantoea dispersa strain GPK (PDG) identified by 16S rRNA gene sequence analysis. HPLC and Mass spectral analysis of metabolites from bacterial spent medium revealed that, IAA production by PDG is Trp-dependent and follows indole-3-pyruvic acid (IPyA) pathway. Substrate specificity study of aromatic amino acid aminotransferase (AAT) showed high activities, only when tryptophan (Trp) and α-ketoglutarate (α-kg) were used as substrates. AAT is highly specific for Trp and α-kg as amino group donor and acceptor, respectively. The effect of exogenous IAA on bacterial growth was established. Low concentration of exogenous IAA induced the growth, whereas high concentration decreased the growth of bacterium. PDG treatment significantly increased the root length, shoot length and dry mass of the chickpea and pigeon pea plants.
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Affiliation(s)
- G B Kulkarni
- Department of Biochemistry, Gulbarga University, Gulbarga, Karnataka, India
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642
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643
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Fernández M, Conde S, Duque E, Ramos JL. In vivo gene expression of Pseudomonas putida KT2440 in the rhizosphere of different plants. Microb Biotechnol 2013; 6:307-13. [PMID: 23433036 PMCID: PMC3815925 DOI: 10.1111/1751-7915.12037] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 12/14/2012] [Accepted: 01/10/2013] [Indexed: 11/29/2022] Open
Abstract
Pseudomonas putida KT2440 has the ability to colonize the rhizosphere of a wide range of plants and can reach cell densities in the range of 105–106 cfu g soil−1. Using the IVET technology we investigated which KT2440 genes were expressed in the rhizosphere of four different plants: pine, cypress, evergreen oak and rosemary. We identified 39 different transcriptional fusions containing the promoters of annotated genes that were preferentially expressed in the rhizosphere. Six of them were expressed in the rhizosphere of all the plant types tested, 11 were expressed in more than one plant and the remaining 22 fusions were found to be expressed in only one type of plant. Another 40 fusions were found to correspond to likely promoters that encode antisense RNAs of unknown function, some of which were isolated as fusions from the bacteria recovered in the rhizosphere from all of the plants, while others were specific to one or several of the plants. The results obtained in this study suggest that plant-specific signals are sensed by KT2440 in the rhizosphere and that the signals and consequent gene expression are related to the bacteria's successful establishment in this niche.
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Affiliation(s)
- Matilde Fernández
- Bio-Iliberis Research and Development, I+D Department, 18210, Peligros, Granada, Spain
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644
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Chalupowicz L, Weinthal D, Gaba V, Sessa G, Barash I, Manulis-Sasson S. Polar auxin transport is essential for gall formation by Pantoea agglomerans on Gypsophila. MOLECULAR PLANT PATHOLOGY 2013; 14:185-90. [PMID: 23083316 PMCID: PMC6638636 DOI: 10.1111/j.1364-3703.2012.00839.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The virulence of the bacterium Pantoea agglomerans pv. gypsophilae (Pag) on Gypsophila paniculata depends on a type III secretion system (T3SS) and its effectors. The hypothesis that plant-derived indole-3-acetic acid (IAA) plays a major role in gall formation was examined by disrupting basipetal polar auxin transport with the specific inhibitors 2,3,5-triiodobenzoic acid (TIBA) and N-1-naphthylphthalamic acid (NPA). On inoculation with Pag, galls developed in gypsophila stems above but not below lanolin rings containing TIBA or NPA, whereas, in controls, galls developed above and below the rings. In contrast, TIBA and NPA could not inhibit tumour formation in tomato caused by Agrobacterium tumefaciens. The colonization of gypsophila stems by Pag was reduced below, but not above, the lanolin-TIBA ring. Following Pag inoculation and TIBA treatment, the expression of hrpL (a T3SS regulator) and pagR (a quorum-sensing transcriptional regulator) decreased four-fold and that of pthG (a T3SS effector) two-fold after 24 h. Expression of PIN2 (a putative auxin efflux carrier) increased 35-fold, 24 h after Pag inoculation. However, inoculation with a mutant in the T3SS effector pthG reduced the expression of PIN2 by two-fold compared with wild-type infection. The results suggest that pthG might govern the elevation of PIN2 expression during infection, and that polar auxin transport-derived IAA is essential for gall initiation.
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Affiliation(s)
- Laura Chalupowicz
- Department of Plant Pathology and Weed Research, ARO, Volcani Center, Bet Dagan 50250, Israel
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645
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In vitro and in vivo inoculation of four endophytic bacteria on Lycopersicon esculentum. N Biotechnol 2013; 30:666-74. [PMID: 23352842 DOI: 10.1016/j.nbt.2013.01.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 12/21/2012] [Accepted: 01/11/2013] [Indexed: 11/20/2022]
Abstract
Four bacteria selected on the basis of their capability of fixing atmospheric nitrogen, stimulating plant-growth, and protecting the host plant from pathogens - Azospirillum brasilense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, Burkholderia ambifaria - were inoculated on tomato seeds either singularly, in couple and in a four bacteria mixer. Aim of this research was to evaluate: (1) effect of single and mixed cultures on the inoculated plant - plant growth, dry weight, root length and surface, number of leaves, among others; (2) colonization and interactions of the bacteria inside the host plant; (3) localization inside the host of single bacterial strains marked with the gusA reporter gene. The results obtained indicate that all selected microbial strains have colonized Lycopersicon esculentum but in a different way, depending on the single species. A. brasilense, G. diazotrophicus inoculated in vitro singularly and together were the best plant colonizers. In vivo essays, instead, B. ambifaria and the four-bacteria mixer gave the best results. It was possible to localize both A. brasilense and H. seropedicae inside the plant by the gusA reporter gene. The bacterial strains occur along the root axis from the apical zone until to the basal stem, on the shoot from the base up to the leaves. The four bacteria actively colonize tomato seeds and establish an endophytic community inside the plant. This review gives new information about colonization processes, in particular how bacteria interact with plants and whether they are likely to establish themselves in the plant environment after field application as biofertilizers or biocontrol agents.
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Kulkarni GB, Sanjeevkumar S, Kirankumar B, Santoshkumar M, Karegoudar TB. Indole-3-acetic acid biosynthesis in Fusarium delphinoides strain GPK, a causal agent of Wilt in Chickpea. Appl Biochem Biotechnol 2013; 169:1292-305. [PMID: 23306880 DOI: 10.1007/s12010-012-0037-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 12/17/2012] [Indexed: 11/24/2022]
Abstract
Fusarium delphinoides (Ascomycota; Nectriaceae) is an indole-3-acetic acid (IAA) producing plant pathogen and a causal agent of wilt in chickpea. The IAA biosynthetic pathway in F. delphinoides strain GPK (FDG) was examined by analyzing metabolic intermediates and by feeding experiments. Gas chromatograph (GC) analysis of FDG culture filtrates showed the presence of metabolic intermediates of indole-3-pyruvic acid (IPyA), indole-3-acetamide (IAM), and tryptamine (TRA) pathways. The different IAA biosynthetic pathways were further confirmed by identifying the presence of different enzymes of these pathways. Substrate specificity study of aromatic amino acid aminotransferase revealed that the enzyme is highly specific for tryptophan (Trp) and α-ketoglutarate (α-kg) as amino group donor and acceptor, respectively. Furthermore, the concentration-dependent effect of exogenous IAA on fungal growth was established. Low concentration of exogenous IAA increases the fungal growth and at high concentration it decreases the growth of FDG.
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647
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Iqbal A, Hasnain S. Auxin Producing <i>Pseudomonas</i> Strains: Biological Candidates to Modulate the Growth of <i>Triticum aestivum</i> Beneficially. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/ajps.2013.49206] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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648
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Mitter B, Brader G, Afzal M, Compant S, Naveed M, Trognitz F, Sessitsch A. Advances in Elucidating Beneficial Interactions Between Plants, Soil, and Bacteria. ADVANCES IN AGRONOMY 2013:381-445. [PMID: 0 DOI: 10.1016/b978-0-12-407685-3.00007-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
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649
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Huang GH, Tian HH, Liu HY, Fan XW, Liang Y, Li YZ. Characterization of plant-growth-promoting effects and concurrent promotion of heavy metal accumulation in the tissues of the plants grown in the polluted soil by Burkholderia strain LD-11. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2013; 15:991-1009. [PMID: 23819291 DOI: 10.1080/15226514.2012.751354] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Plant-growth-promoting (PGP) bacteria especially with the resistance to multiple heavy metals are helpful to phytoremediation. Further development of PGP bacteria is very necessary because of the extreme diversity of plants, soils, and heavy metal pollution. A Burkholderia sp. strain, numbered LD-11, was isolated, which showed resistances to multiple heavy metals and antibiotics. It can produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase and siderophores. Inoculation with the LD-11 improved germination of seeds of the investigated vegetable plants in the presence of Cu, promoted elongation of roots and hypocotyledonary axes, enhanced the dry weights of the plants grown in the soils polluted with Cu and/or Pb, and increased activity of the soil urease and the rhizobacteria diversity. Inoculation with the LD-11 significantly enhanced Cu and/or Pb accumulation especially in the roots of the plants grown in the polluted soils. Notably, LD-11 could produce siderophores in the presence of Cu. Conclusively, the PGP effects and concurrent heavy metal accumulation in the plant tissues results from combined effects of the above-mentioned multiple factors. Cu is an important element that represses production of the siderophore by the bacteria. Phytoremediation by synergistic use of the investigated plants and the bacterial strain LD-11 is a phytoextraction process.
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Affiliation(s)
- Gui-Hai Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, Guangxi University, Nanning, Guangxi, China
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Bulgarelli D, Schlaeppi K, Spaepen S, Ver Loren van Themaat E, Schulze-Lefert P. Structure and functions of the bacterial microbiota of plants. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:807-38. [PMID: 23373698 DOI: 10.1146/annurev-arplant-050312-120106] [Citation(s) in RCA: 1415] [Impact Index Per Article: 128.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Plants host distinct bacterial communities on and inside various plant organs, of which those associated with roots and the leaf surface are best characterized. The phylogenetic composition of these communities is defined by relatively few bacterial phyla, including Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. A synthesis of available data suggests a two-step selection process by which the bacterial microbiota of roots is differentiated from the surrounding soil biome. Rhizodeposition appears to fuel an initial substrate-driven community shift in the rhizosphere, which converges with host genotype-dependent fine-tuning of microbiota profiles in the selection of root endophyte assemblages. Substrate-driven selection also underlies the establishment of phyllosphere communities but takes place solely at the immediate leaf surface. Both the leaf and root microbiota contain bacteria that provide indirect pathogen protection, but root microbiota members appear to serve additional host functions through the acquisition of nutrients from soil for plant growth. Thus, the plant microbiota emerges as a fundamental trait that includes mutualism enabled through diverse biochemical mechanisms, as revealed by studies on plant growth-promoting and plant health-promoting bacteria.
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Affiliation(s)
- Davide Bulgarelli
- Max Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany
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