751
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Lau S, Shao N, Bock R, Jürgens G, De Smet I. Auxin signaling in algal lineages: fact or myth? TRENDS IN PLANT SCIENCE 2009; 14:182-8. [PMID: 19285905 DOI: 10.1016/j.tplants.2009.01.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 01/08/2009] [Accepted: 01/12/2009] [Indexed: 05/05/2023]
Abstract
Auxin is of major importance throughout the life cycle of a plant, affecting several physiological and developmental processes, such as cell expansion and division. However, the evolutionary time point at which auxin became involved in such diverse processes is currently unclear. Despite some controversy, numerous reports demonstrate the presence of auxin in algal lineages and its effects on algal development, suggesting an early evolutionary origin of auxin-dependent mechanisms. Here, we review these reports and discuss in silico analyses of auxin signaling components. It seems that, at least in microalgae, the assumed major components of auxin signaling in land plants are absent. However, these microalgae might have alternative auxin signaling pathways that could account for their responses to auxin.
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Affiliation(s)
- Steffen Lau
- Center for Plant Molecular Biology (ZMBP), Developmental Genetics, Tübingen University, Auf der Morgenstelle 3, D-72076 Tübingen, Germany
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752
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Kamnev AA, Kovács K, Kuzmann E, Vértes A. Application of Mössbauer spectroscopy for studying chemical effects of environmental factors on microbial signalling: Redox processes involving iron(III) and some microbial autoinducer molecules. J Mol Struct 2009. [DOI: 10.1016/j.molstruc.2008.11.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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753
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Kurosawa N, Hirata T, Suzuki H. Characterization of putative tryptophan monooxygenase from Ralstonia solanasearum. J Biochem 2009; 146:23-32. [DOI: 10.1093/jb/mvp040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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754
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Production of the phytohormone indole-3-acetic acid by estuarine species of the genus Vibrio. Appl Environ Microbiol 2009; 75:2253-8. [PMID: 19218411 DOI: 10.1128/aem.02072-08] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Strains of Vibrio spp. isolated from roots of the estuarine grasses Spartina alterniflora and Juncus roemerianus produce the phytohormone indole-3-acetic acid (IAA). The colorimetric Salkowski assay was used for initial screening of IAA production. Gas chromatography-mass spectroscopy (GC-MS) was then employed to confirm and quantify IAA production. The accuracy of IAA quantification by the Salkowski assay was examined by comparison to GC-MS assay values. Indole-3-acetamide, an intermediate in IAA biosynthesis by the indole-3-acetamide pathway, was also identified by GC-MS. Multilocus sequence typing of concatenated 16S rRNA, recA, and rpoA genes was used for phylogenetic analysis of environmental isolates within the genus Vibrio. Eight Vibrio type strains and five additional species-level clades containing a total of 16 environmental isolates and representing five presumptive new species were identified as IAA-producing Vibrio species. Six additional environmental isolates similar to four of the Vibrio type strains were also IAA producers. To our knowledge, this is the first report of IAA production by species of the genus Vibrio or by bacteria isolated from an estuarine environment.
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755
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Lee DS, Kim BK, Kwon SJ, Jin HC, Park OK. Arabidopsis GDSL lipase 2 plays a role in pathogen defense via negative regulation of auxin signaling. Biochem Biophys Res Commun 2009; 379:1038-42. [DOI: 10.1016/j.bbrc.2009.01.006] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Accepted: 01/03/2009] [Indexed: 10/21/2022]
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756
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Mandal SM, Mandal S, Mandal M, Das AK, Das A, Pati BR, Pati B, Ghosh AK, Ghosh A. Stimulation of indoleacetic acid production in a Rhizobium isolate of Vigna mungo by root nodule phenolic acids. Arch Microbiol 2009; 191:389-93. [PMID: 19151966 DOI: 10.1007/s00203-008-0455-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 12/17/2008] [Accepted: 12/23/2008] [Indexed: 11/24/2022]
Abstract
The influence of endogenous root nodules phenolic acids on indoleacetic acid (IAA) production by its symbiont (Rhizobium) was examined. The root nodules contain higher amount of IAA and phenolic acids than non-nodulated roots. Presence of IAA metabolizing enzymes, IAA oxidase, peroxidase, and polyphenol oxidase indicate the metabolism of IAA in the nodules and roots. Three most abundant endogenous root nodule phenolic acids (protocatechuic acid, 4-hydroxybenzaldehyde and p-coumaric acid) have been identified and their effects on IAA production by the symbiont have been studied in L-tryptophan supplemented yeast extract basal medium. Protocatechuic acid (1.5 microg ml(-1)) showed maximum stimulation (2.15-fold over control) of IAA production in rhizobial culture. These results indicate that the phenolic acids present in the nodule might serve as a stimulator for IAA production by the symbiont (Rhizobium).
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Affiliation(s)
- Santi M Mandal
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, India
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757
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Barash I, Manulis-Sasson S. Recent evolution of bacterial pathogens: the gall-forming Pantoea agglomerans case. ANNUAL REVIEW OF PHYTOPATHOLOGY 2009; 47:133-52. [PMID: 19400643 DOI: 10.1146/annurev-phyto-080508-081803] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Pantoea agglomerans, a widespread epiphyte and commensal bacterium, has evolved into an Hrp-dependent and host-specific tumorigenic pathogen by acquiring a plasmid containing a pathogenicity island (PAI). The PAI was evolved on an iteron plasmid of the IncN family, which is distributed among genetically diverse populations of P. agglomerans. The structure of the PAI supports the premise of a recently evolved pathogen. This review offers insight into a unique model for emergence of new bacterial pathogens. It illustrates how horizontal gene transfer was the major driving force in the creation of the PAI, although a pathoadaptive mechanism might also be involved. It describes the crucial function of plant-produced indole-3-acetic acid (IAA) and cytokinines (CK) in gall initiation as opposed to the significant but secondary role of pathogen-secreted phytohormones. It also unveils the role of type III effectors in determination of host specificity and evolution of the pathogen into pathovars. Finally, it describes how interactions between the quorum sensing system, hrp regulatory genes, and bacterially secreted IAA or CKs affect gall formation and epiphytic fitness.
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Affiliation(s)
- Isaac Barash
- Department of Plant Sciences, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 61390, Israel.
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758
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Bianco C, Defez R. Medicago truncatula improves salt tolerance when nodulated by an indole-3-acetic acid-overproducing Sinorhizobium meliloti strain. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:3097-107. [PMID: 19436044 DOI: 10.1093/jxb/erp140] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The abiotic stress resistance of wild-type Sinorhizobium meliloti 1021 was compared with that of RD64, a derivative of the 1021 strain harbouring an additional pathway for the synthesis of indole-3-acetic acid (IAA), expressed in both free-living bacteria and bacteroids. It is shown here that the IAA-overproducing RD64 strain accumulated a higher level of trehalose as its endogenous osmolyte and showed an increased tolerance to several stress conditions (55 degrees C, 4 degrees C, UV-irradiation, 0.5 M NaCl, and pH 3). Medicago truncatula plants nodulated by RD64 (Mt-RD64) showed re-modulation of phytohormones, with a higher IAA content in nodules and roots and a decreased IAA level in shoots as compared with plants nodulated by the wild-type strain 1021 (Mt-1021). The response of nodulated M. truncatula plants to salt stress, when 0.3 M NaCl was applied, was analysed. For Mt-RD64 plants higher internal proline contents, almost unchanged hydrogen peroxide levels, and enhanced activity of antioxidant enzymes (superoxide dismutase, total peroxidase, glutathione reductase, and ascorbate peroxidase) were found compared with Mt-1021 plants. These results were positively correlated with reduced symptoms of senescence, lower expression of ethylene signalling genes, lower reduction of shoot dry weight, and better nitrogen-fixing capacity observed for these plants. Upon re-watering, after 0.3 M NaCl treatment, Mt-1021 plants almost die whereas Mt-RD64 plants showed visual signs of recovery. Finally, the shoot dry weight of Mt-RD64 plants treated with 0.15 M NaCl was not statistically different from that of Mt-1021 plants grown under non-stressed conditions.
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Affiliation(s)
- Carmen Bianco
- Institute of Genetics and Biophysics Adriano Buzzati Traverso, via P. Castellino 111, 80131 Naples, Italy
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759
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Spaepen S, Das F, Luyten E, Michiels J, Vanderleyden J. Indole-3-acetic acid-regulated genes in Rhizobium etli CNPAF512. FEMS Microbiol Lett 2008; 291:195-200. [PMID: 19087205 DOI: 10.1111/j.1574-6968.2008.01453.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In the rhizosphere and their interaction with plants rhizobia encounter many different plant compounds, including phytohormones like auxins. Moreover, some rhizobial strains are capable of producing the auxin, indole-3-acetic acid (IAA). However, the role of IAA for the bacterial partner in the legume-Rhizobium symbiosis is not known. To identify the effect of IAA on rhizobial gene expression, a transposon (mTn5gusA-oriV) mutant library of Rhizobium etli, enriched for mutants that show differential gene expression under microaerobiosis and/or addition of nodule extracts as compared with control conditions, was screened for altered gene expression upon IAA addition. Four genes were found to be regulated by IAA. These genes appear to be involved in plant signal processing, motility or attachment to plant roots, clearly demonstrating a distinct role for IAA in legume-Rhizobium interactions.
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Affiliation(s)
- Stijn Spaepen
- Centre of Microbial and Plant Genetics and INPAC, K.U. Leuven, Heverlee, Belgium
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760
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Abstract
This review describes secondary metabolites that have been shown to be synthesized by symbiotic bacteria, or for which this possibility has been discussed. It includes 365 references.
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Affiliation(s)
- Jörn Piel
- Kekulé-Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany.
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761
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Ryu RJ, Patten CL. Aromatic amino acid-dependent expression of indole-3-pyruvate decarboxylase is regulated by TyrR in Enterobacter cloacae UW5. J Bacteriol 2008; 190:7200-8. [PMID: 18757531 PMCID: PMC2580706 DOI: 10.1128/jb.00804-08] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2008] [Accepted: 08/22/2008] [Indexed: 11/20/2022] Open
Abstract
The plant growth-promoting rhizobacterium Enterobacter cloacae UW5 synthesizes the plant growth hormone indole-3-acetic acid (IAA) via the indole-3-pyruvate pathway utilizing the enzyme indole-3-pyruvate decarboxylase that is encoded by ipdC. In this bacterium, ipdC expression and IAA production occur in stationary phase and are induced by an exogenous source of tryptophan, conditions that are present in the rhizosphere. The aim of this study was to identify the regulatory protein that controls the expression of ipdC. We identified a sequence in the promoter region of ipdC that is highly similar to the recognition sequence for the Escherichia coli regulatory protein TyrR that regulates genes involved in aromatic amino acid transport and metabolism. Using a tyrR insertional mutant, we demonstrate that TyrR is required for IAA production and for induction of ipdC transcription. TyrR directly induces ipdC expression, as was determined by real-time quantitative reverse transcription-PCR, by ipdC promoter-driven reporter gene activity, and by electrophoretic mobility shift assays. Expression increases in response to tryptophan, phenylalanine, and tyrosine. This suggests that, in addition to its function in plant growth promotion, indolepyruvate decarboxylase may be important for aromatic amino acid uptake and/or metabolism.
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Affiliation(s)
- R Julie Ryu
- Biology Department, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada
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762
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Dias ACF, Costa FEC, Andreote FD, Lacava PT, Teixeira MA, Assumpção LC, Araújo WL, Azevedo JL, Melo IS. Isolation of micropropagated strawberry endophytic bacteria and assessment of their potential for plant growth promotion. World J Microbiol Biotechnol 2008. [DOI: 10.1007/s11274-008-9878-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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763
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Mathesius U. Auxin: at the root of nodule development? FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:651-668. [PMID: 32688821 DOI: 10.1071/fp08177] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Accepted: 08/14/2008] [Indexed: 06/11/2023]
Abstract
Root nodules are formed as a result of an orchestrated exchange of chemical signals between symbiotic nitrogen fixing bacteria and certain plants. In plants that form nodules in symbiosis with actinorhizal bacteria, nodules are derived from lateral roots. In most legumes, nodules are formed de novo from pericycle and cortical cells that are re-stimulated for division and differentiation by rhizobia. The ability of plants to nodulate has only evolved recently and it has, therefore, been suggested that nodule development is likely to have co-opted existing mechanisms for development and differentiation from lateral root formation. Auxin is an important regulator of cell division and differentiation, and changes in auxin accumulation and transport are essential for lateral root development. There is growing evidence that rhizobia alter the root auxin balance as a prerequisite for nodule formation, and that nodule numbers are regulated by shoot-to-root auxin transport. Whereas auxin requirements appear to be similar for lateral root and nodule primordium activation and organ differentiation, the major difference between the two developmental programs lies in the specification of founder cells. It is suggested that differing ratios of auxin and cytokinin are likely to specify the precursors of the different root organs.
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Affiliation(s)
- Ulrike Mathesius
- School of Biochemistry and Molecular Biology, Australian National University and Australian Research Council Centre of Excellence for Integrative Legume Research, Linnaeus Way, Canberra, ACT 0200, Australia. Email
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764
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Joint immobilization of plant growth-promoting bacteria and green microalgae in alginate beads as an experimental model for studying plant-bacterium interactions. Appl Environ Microbiol 2008; 74:6797-802. [PMID: 18791009 DOI: 10.1128/aem.00518-08] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A simple, quantitative experimental model, offering a convenient and basic approach to studies of plant-bacterium interactions, is proposed. This involves immobilizing a unicellular, freshwater microalga, a Chlorella species, serving as the plant, with a plant growth-promoting bacterium, an Azospirillum species, in small alginate beads to allow close interaction and to avoid external interference from bacterial contaminants.
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765
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Hardoim PR, van Overbeek LS, Elsas JDV. Properties of bacterial endophytes and their proposed role in plant growth. Trends Microbiol 2008; 16:463-71. [PMID: 18789693 DOI: 10.1016/j.tim.2008.07.008] [Citation(s) in RCA: 674] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 06/26/2008] [Accepted: 07/14/2008] [Indexed: 01/25/2023]
Abstract
Bacterial endophytes live inside plants for at least part of their life cycle. Studies of the interaction of endophytes with their host plants and their function within their hosts are important to address the ecological relevance of endophytes. The modulation of ethylene levels in plants by bacterially produced 1-aminocyclopropane-1-carboxylate deaminase is a key trait that enables interference with the physiology of the host plant. Endophytes with this capacity might profit from association with the plant, because colonization is enhanced. In turn, host plants benefit by stress reduction and increased root growth. This mechanism leads to the concept of 'competent' endophytes, defined as endophytes that are equipped with genes important for maintenance of plant-endophyte associations. The ecological role of these endophytes and their relevance for plant growth are discussed here.
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Affiliation(s)
- Pablo R Hardoim
- Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
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766
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Yuan ZC, Haudecoeur E, Faure D, Kerr KF, Nester EW. Comparative transcriptome analysis of Agrobacterium tumefaciens in response to plant signal salicylic acid, indole-3-acetic acid and gamma-amino butyric acid reveals signalling cross-talk and Agrobacterium--plant co-evolution. Cell Microbiol 2008; 10:2339-54. [PMID: 18671824 DOI: 10.1111/j.1462-5822.2008.01215.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Agrobacterium has evolved sophisticated strategies to perceive and transduce plant-derived cues. Recent studies have found that numerous plant signals, including salicylic acid (SA), indole-3-acetic acid (IAA) and gamma-amino butyric acid (GABA), profoundly affect Agrobacterium-plant interactions. Here we determine and compare the transcriptome profiles of Agrobacterium in response to these three plant signals. Collectively, the transcription of 103, 115 and 95 genes was significantly altered by SA, IAA and GABA respectively. Both distinct cellular responses and overlapping signalling pathways were elicited by these three plant signals. Interestingly, these three plant compounds function additively to shut off the Agrobacterium virulence programme and activate the quorum-quenching machinery. Moreover, the repression of the virulence programme by SA and IAA and the inactivation of quorum-sensing signals by SA and GABA are regulated through independent pathways. Our data indicate that these plant signals, while cross-talk in plant signalling networks, also act as cross-kingdom signals and play redundant roles in tailoring Agrobacterium regulatory pathways, resulting in intensive signalling cross-talk in Agrobacterium. Our results support the notion that Agrobacterium has evolved the ability to hijack plant signals for its own benefit. The complex signalling interplay between Agrobacterium and its plant hosts reflects an exquisite co-evolutionary balance.
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Affiliation(s)
- Ze-Chun Yuan
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
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767
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De-Bashan LE, Antoun H, Bashan Y. INVOLVEMENT OF INDOLE-3-ACETIC ACID PRODUCED BY THE GROWTH-PROMOTING BACTERIUM AZOSPIRILLUM SPP. IN PROMOTING GROWTH OF CHLORELLA VULGARIS(1). JOURNAL OF PHYCOLOGY 2008; 44:938-47. [PMID: 27041612 DOI: 10.1111/j.1529-8817.2008.00533.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Involvement of indole-3-acetic acid (IAA), produced by the microalgae-growth-promoting bacteria Azospirillum brasilens and A. lipoferum, in promoting growth of the microalga Chlorella vulgaris Beij. was studied. Four wildtype strains of Azospirillum and their IAA-deficient mutants were co-immobilized with C. vulgaris in alginate beads. Cultures were grown in synthetic growth medium supplemented with tryptophan. Growth promotion of microalgae and production of exogenous IAA by Azospirillum spp. were monitored. All wildtype Azospirillum spp. produced significant but varying amounts of IAA, while their mutant forms produced significantly less. The results demonstrated a significant growth promotion in Chlorella cultures when immobilized with the four wildtype strains of Azospirillum, while very low or no enhanced growth was induced by the four IAA-deficient mutants, compared to when C. vulgaris is immobilized alone. A complementation experiment, where an IAA-attenuated mutant (A. brasilense SpM7918) was supplemented with IAA produced by its parental wildtype strain (A. brasilense Sp6), restored growth promotion in the microalgae-mutant culture.
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Affiliation(s)
- Luz E De-Bashan
- Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USADépartment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USA
| | - Hani Antoun
- Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USADépartment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USA
| | - Yoav Bashan
- Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USADépartment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), La Paz, B.C.S. 23090, Mexico Départment des Sols et de Génie Agroalimentaire, Université Laval, Québec City, Québec, Canada Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, Arizona, USA
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768
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Long HH, Schmidt DD, Baldwin IT. Native bacterial endophytes promote host growth in a species-specific manner; phytohormone manipulations do not result in common growth responses. PLoS One 2008; 3:e2702. [PMID: 18628963 PMCID: PMC2444036 DOI: 10.1371/journal.pone.0002702] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 06/19/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND All plants in nature harbor a diverse community of endophytic bacteria which can positively affect host plant growth. Changes in plant growth frequently reflect alterations in phytohormone homoeostasis by plant-growth-promoting (PGP) rhizobacteria which can decrease ethylene (ET) levels enzymatically by 1-aminocyclopropane-1-carboxylate (ACC) deaminase or produce indole acetic acid (IAA). Whether these common PGP mechanisms work similarly for different plant species has not been rigorously tested. METHODOLOGY/PRINCIPAL FINDINGS We isolated bacterial endophytes from field-grown Solanum nigrum; characterized PGP traits (ACC deaminase activity, IAA production, phosphate solubilization and seedling colonization); and determined their effects on their host, S. nigrum, as well as on another Solanaceous native plant, Nicotiana attenuata. In S. nigrum, a majority of isolates that promoted root growth were associated with ACC deaminase activity and IAA production. However, in N. attenuata, IAA but not ACC deaminase activity was associated with root growth. Inoculating N. attenuata and S. nigrum with known PGP bacteria from a culture collection (DSMZ) reinforced the conclusion that the PGP effects are not highly conserved. CONCLUSIONS/SIGNIFICANCE We conclude that natural endophytic bacteria with PGP traits do not have general and predictable effects on the growth and fitness of all host plants, although the underlying mechanisms are conserved.
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Affiliation(s)
- Hoang Hoa Long
- Max Planck Institute for Chemical Ecology, Jena, Germany
| | | | - Ian T. Baldwin
- Max Planck Institute for Chemical Ecology, Jena, Germany
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769
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Da Mota FF, Gomes EA, Seldin L. Auxin production and detection of the gene coding for the Auxin Efflux Carrier (AEC) protein in Paenibacillus polymyxa. J Microbiol 2008; 46:257-64. [DOI: 10.1007/s12275-007-0245-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 04/01/2008] [Indexed: 11/29/2022]
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770
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Molina-Favero C, Creus CM, Simontacchi M, Puntarulo S, Lamattina L. Aerobic nitric oxide production by Azospirillum brasilense Sp245 and its influence on root architecture in tomato. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:1001-1009. [PMID: 18533840 DOI: 10.1094/mpmi-21-7-1001] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The major feature of the plant-growth-promoting bacteria Azospirillum brasilense is its ability to modify plant root architecture. In plants, nitric oxide (NO) mediates indole-3-acetic acid (IAA)-signaling pathways leading to both lateral (LR) and adventitious (AR) root formation. Here, we analyzed aerobic NO production by A. brasilense Sp245 wild type (wt) and its mutants Faj009 (IAA-attenuated) and Faj164 (periplasmic nitrate reductase negative), and its correlation with tomato root-growth-promoting effects. The wt and Faj009 strains produced 120 nmol NO per gram of bacteria in aerated nitrate-containing medium. In contrast, Faj164 produced 5.6 nmol NO per gram of bacteria, indicating that aerobic denitrification could be considered an important source of NO. Inoculation of tomato (Solanum lycopersicum Mill.) seedlings with both wt and Faj009 induced LR and AR development. In contrast, Faj164 mutant was not able to promote LR or AR when seedlings grew in nitrate. When NO was removed with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), both LR and AR formation were inhibited, providing evidence that NO mediated Azospirillum-induced root branching. These results show that aerobic NO synthesis in A. brasilense could be achieved by different pathways and give evidence for an NO-dependent promoting activity on tomato root branching regardless of bacterial capacity for IAA synthesis.
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Affiliation(s)
- Celeste Molina-Favero
- Area Biomolecular, Unidad Integrada Balcarce, Instituto Nacional de Tecnología Agropecuaria-Universidad Nacional de Mar del Plata. Km 73,5 Ruta 226 (7620) Balcarce, Argentina
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771
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Reineke G, Heinze B, Schirawski J, Buettner H, Kahmann R, Basse CW. Indole-3-acetic acid (IAA) biosynthesis in the smut fungus Ustilago maydis and its relevance for increased IAA levels in infected tissue and host tumour formation. MOLECULAR PLANT PATHOLOGY 2008; 9:339-55. [PMID: 18705875 PMCID: PMC6640242 DOI: 10.1111/j.1364-3703.2008.00470.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Infection of maize (Zea mays) plants with the smut fungus Ustilago maydis is characterized by excessive host tumour formation. U. maydis is able to produce indole-3-acetic acid (IAA) efficiently from tryptophan. To assess a possible connection to the induction of host tumours, we investigated the pathways leading to fungal IAA biosynthesis. Besides the previously identified iad1 gene, we identified a second indole-3-acetaldehyde dehydrogenase gene, iad2. Deltaiad1Deltaiad2 mutants were blocked in the conversion of both indole-3-acetaldehyde and tryptamine to IAA, although the reduction in IAA formation from tryptophan was not significantly different from Deltaiad1 mutants. To assess an influence of indole-3-pyruvic acid on IAA formation, we deleted the aromatic amino acid aminotransferase genes tam1 and tam2 in Deltaiad1Deltaiad2 mutants. This revealed a further reduction in IAA levels by five- and tenfold in mutant strains harbouring theDeltatam1 andDeltatam1Deltatam2 deletions, respectively. This illustrates that indole-3-pyruvic acid serves as an efficient precursor for IAA formation in U. maydis. Interestingly, the rise in host IAA levels upon U. maydis infection was significantly reduced in tissue infected with Deltaiad1Deltaiad2Deltatam1 orDeltaiad1Deltaiad2Deltatam1Deltatam2 mutants, whereas induction of tumours was not compromised. Together, these results indicate that fungal IAA production critically contributes to IAA levels in infected tissue, but this is apparently not important for triggering host tumour formation.
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Affiliation(s)
- Gavin Reineke
- Max-Planck-Institute for Terrestrial Microbiology, Department of Organismic Interactions, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany
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772
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Zuther K, Mayser P, Hettwer U, Wu W, Spiteller P, Kindler BLJ, Karlovsky P, Basse CW, Schirawski J. The tryptophan aminotransferase Tam1 catalyses the single biosynthetic step for tryptophan-dependent pigment synthesis in Ustilago maydis. Mol Microbiol 2008; 68:152-72. [DOI: 10.1111/j.1365-2958.2008.06144.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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773
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Johri MM. Hormonal regulation in green plant lineage families. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2008; 14:23-38. [PMID: 23572871 PMCID: PMC3550668 DOI: 10.1007/s12298-008-0003-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The patterns of phytohormones distribution, their native function and possible origin of hormonal regulation across the green plant lineages (chlorophytes, charophytes, bryophytes and tracheophytes) are discussed. The five classical phytohormones - auxins, cytokinins, gibberellins (GA), abscisic acid (ABA) and ethylene occur ubiquitously in green plants. They are produced as secondary metabolites by microorganisms. Some of the bacterial species use phytohormones to interact with the plant as a part of their colonization strategy. Phytohormone biosynthetic pathways in plants seem to be of microbial origin and furthermore, the origin of high affinity perception mechanism could have preceded the recruitment of a metabolite as a hormone. The bryophytes represent the earliest land plants which respond to the phytohormones with the exception of gibberellins. The regulation by auxin and ABA may have evolved before the separation of green algal lineage. Auxin enhances rhizoid and caulonemal differentiation while cytokinins enhance shoot bud formation in mosses. Ethylene retards cell division but seems to promote cell elongation. The presence of responses specific to cytokinins and ethylene strongly suggest the origin of their regulation in bryophytes. The hormonal role of GAs could have evolved in some of the ferns where antheridiogens (compounds related to GAs) and GAs themselves regulate the formation of antheridia. During migration of life forms to land, the tolerance to desiccation may have evolved and is now observed in some of the microorganisms, animals and plants. Besides plants, sequences coding for late embryogenesis abundant-like proteins occur in the genomes of other anhydrobiotic species of microorganisms and nematodes. ABA acts as a stress signal and increases rapidly upon desiccation or in response to some of the abiotic stresses in green plants. As the salt stress also increases ABA release in the culture medium of cyanobacterium Trichormus variabilis, the recruitment of ABA in the regulation of stress responses could have been derived from prokaryotes and present at the level of common ancestor of green plants. The overall hormonal action mechanisms in mosses are remarkably similar to that of the higher plants. As plants are thought to be monophyletic in origin, the existence of remarkably similar hormonal mechanisms in the mosses and higher plants, suggests that some of the basic elements of regulation cascade could have also evolved at the level of common ancestor of plants. The networking of various steps in a cascade or the crosstalk between different cascades is variable and reflects the dynamic interaction between a species and its specific environment.
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Affiliation(s)
- M. M. Johri
- />Formerly from Department of Biological Sciences, TIFR, Mumbai, India
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774
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Malhotra M, Srivastava S. Organization of the ipdC region regulates IAA levels in different Azospirillum brasilense strains: molecular and functional analysis of ipdC in strain SM. Environ Microbiol 2008; 10:1365-73. [PMID: 18248455 DOI: 10.1111/j.1462-2920.2007.01529.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Presence of the indole-3-pyruvic acid pathway (IPyA) of indole-3-acetic acid (IAA) biosynthesis was demonstrated by identifying the ipdC gene encoding indole-3-pyruvate decarboxylase (IPDC) in Azospirillum brasilense strain SM. Comparison with other A. brasilense strains, Sp7 and Sp245, revealed homology in the gene and its 5' regulatory region. The 3' region of strain SM carries a truncated iaaC gene implicated in controlling IAA biosynthesis in strain Sp245. While the ipdC transcript could be visualized by reverse transcription polymerase chain reaction (RT-PCR), truncated iaaC was non-functional. Strain SM derivatives carrying higher copy number of ipdC and P(ipdC) showed improved IAA biosynthesis. P(ipdC) showed sequence elements that are part of composite auxin-responsive promoters. Expression of ipdC was upregulated by IAA, other auxins, temperature and nutrient stress, and an increase in pH. Heterologous overexpression of a functional iaaC gene from strain Sp245 in strain SM confirmed its role in controlling IAA biosynthesis and lowering ipdC expression which may be effected by dissociating IAA-transcriptional regulator interactions in the 5' region. However, the effect of the introduced iaaC was overcome when both ipdC and iaaC were expressed from similar plasmid background. This analysis confirmed that strain-based differences in IAA biosynthesis could be explained by differential regulation of ipdC expression.
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Affiliation(s)
- Mandira Malhotra
- Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021, India
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775
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Leveau JHJ, Gerards S. Discovery of a bacterial gene cluster for catabolism of the plant hormone indole 3-acetic acid. FEMS Microbiol Ecol 2008; 65:238-50. [PMID: 18205812 DOI: 10.1111/j.1574-6941.2008.00436.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The isolation and annotation of an 8994-bp DNA fragment from Pseudomonas putida 1290, which conferred upon P. putida KT2440 the ability to utilize the plant hormone indole 3-acetic acid (IAA) as a sole source of carbon and energy, is described. This iac locus (for indole 3-acetic acid catabolism) was identified through analysis of a plasposon mutant of P. putida 1290 that was no longer able to grow on IAA or indole 3-acetaldehyde and was unable to protect radish roots from stunting by exogenously added IAA. The iac locus consisted of 10 genes with coding similarity to enzymes acting on indole or amidated aromatics and to proteins with regulatory or unknown function. Highly similar iac gene clusters were identified in the genomes of 22 bacterial species. Five of these, i.e. P. putida GB-1, Marinomonas sp. MWYL1, Burkholderia sp. 383, Sphingomonas wittichii RW1 and Rhodococcus sp. RHA1, were tested to confirm that bacteria with IAA-degrading ability have representatives in the Alpha-, Beta- and Gammaproteobacteria and in the Actinobacteria. In P. putida 1290, cat and pca genes were found to be essential to IAA-degradation, suggesting that IAA is channeled via catechol into the beta-ketoadipate pathway. Also contributing to the IAA degrading phenotype were genes involved in tricarboxylate cycling, gluconeogenesis, and carbon/nitrogen sensing.
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Affiliation(s)
- Johan H J Leveau
- Netherlands Institute of Ecology (NIOO-KNAW), Heteren, The Netherlands.
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776
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777
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Malhotra M, Srivastava S. An ipdC gene knock-out of Azospirillum brasilense strain SM and its implications on indole-3-acetic acid biosynthesis and plant growth promotion. Antonie van Leeuwenhoek 2007; 93:425-33. [PMID: 17952626 DOI: 10.1007/s10482-007-9207-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Accepted: 10/08/2007] [Indexed: 10/22/2022]
Abstract
The indole-3-pyruvate decarboxylase gene (ipdC), coding for a key enzyme of the indole-3-pyruvic acid pathway of IAA biosynthesis in Azospirillum brasilense SM was functionally disrupted in a site-specific manner. This disruption was brought about by group II intron-based Targetron gene knock-out system as other conventional methods were unsuccessful in generating an IAA-attenuated mutant. Intron insertion was targeted to position 568 on the sense strand of ipdC, resulting in the knock-out strain, SMIT568s10 which showed a significant (~50%) decrease in the levels of indole-3-acetic acid, indole-3-acetaldehyde and tryptophol compared to the wild type strain SM. In addition, a significant decrease in indole-3-pyruvate decarboxylase enzyme activity by approximately 50% was identified confirming a functional knock-out. Consequently, a reduction in the plant growth promoting response of strain SMIT568s10 was observed in terms of root length and lateral root proliferation as well as the total dry weight of the treated plants. Residual indole-3-pyruvate decarboxylase enzyme activity, and indole-3-acetic acid, tryptophol and indole-3-acetaldehyde formed along with the plant growth promoting response by strain SMIT568s10 in comparison with an untreated set suggest the presence of more than one copy of ipdC in the A. brasilense SM genome.
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Affiliation(s)
- Mandira Malhotra
- Department of Genetics, University of Delhi South Campus, New Delhi, India
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778
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Zhang Z, Li Q, Li Z, Staswick PE, Wang M, Zhu Y, He Z. Dual regulation role of GH3.5 in salicylic acid and auxin signaling during Arabidopsis-Pseudomonas syringae interaction. PLANT PHYSIOLOGY 2007; 145:450-64. [PMID: 17704230 PMCID: PMC2048736 DOI: 10.1104/pp.107.106021] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 08/09/2007] [Indexed: 05/16/2023]
Abstract
Salicylic acid (SA) plays a central role in plant disease resistance, and emerging evidence indicates that auxin, an essential plant hormone in regulating plant growth and development, is involved in plant disease susceptibility. GH3.5, a member of the GH3 family of early auxin-responsive genes in Arabidopsis (Arabidopsis thaliana), encodes a protein possessing in vitro adenylation activity on both indole-3-acetic acid (IAA) and SA. Here, we show that GH3.5 acts as a bifunctional modulator in both SA and auxin signaling during pathogen infection. Overexpression of the GH3.5 gene in an activation-tagged mutant gh3.5-1D led to elevated accumulation of SA and increased expression of PR-1 in local and systemic tissues in response to avirulent pathogens. In contrast, two T-DNA insertional mutations of GH3.5 partially compromised the systemic acquired resistance associated with diminished PR-1 expression in systemic tissues. The gh3.5-1D mutant also accumulated high levels of free IAA after pathogen infection and impaired different resistance-gene-mediated resistance, which was also observed in the GH3.6 activation-tagged mutant dfl1-D that impacted the auxin pathway, indicating an important role of GH3.5/GH3.6 in disease susceptibility. Furthermore, microarray analysis showed that the SA and auxin pathways were simultaneously augmented in gh3.5-1D after infection with an avirulent pathogen. The SA pathway was amplified by GH3.5 through inducing SA-responsive genes and basal defense components, whereas the auxin pathway was derepressed through up-regulating IAA biosynthesis and down-regulating auxin repressor genes. Taken together, our data reveal novel regulatory functions of GH3.5 in the plant-pathogen interaction.
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Affiliation(s)
- Zhongqin Zhang
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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779
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Spaepen S, Versées W, Gocke D, Pohl M, Steyaert J, Vanderleyden J. Characterization of phenylpyruvate decarboxylase, involved in auxin production of Azospirillum brasilense. J Bacteriol 2007; 189:7626-33. [PMID: 17766418 PMCID: PMC2168738 DOI: 10.1128/jb.00830-07] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Azospirillum brasilense belongs to the plant growth-promoting rhizobacteria with direct growth promotion through the production of the phytohormone indole-3-acetic acid (IAA). A key gene in the production of IAA, annotated as indole-3-pyruvate decarboxylase (ipdC), has been isolated from A. brasilense, and its regulation was reported previously (A. Vande Broek, P. Gysegom, O. Ona, N. Hendrickx, E. Prinsen, J. Van Impe, and J. Vanderleyden, Mol. Plant-Microbe Interact. 18:311-323, 2005). An ipdC-knockout mutant was found to produce only 10% (wt/vol) of the wild-type IAA production level. In this study, the encoded enzyme is characterized via a biochemical and phylogenetic analysis. Therefore, the recombinant enzyme was expressed and purified via heterologous overexpression in Escherichia coli and subsequent affinity chromatography. The molecular mass of the holoenzyme was determined by size-exclusion chromatography, suggesting a tetrameric structure, which is typical for 2-keto acid decarboxylases. The enzyme shows the highest kcat value for phenylpyruvate. Comparing values for the specificity constant kcat/Km, indole-3-pyruvate is converted 10-fold less efficiently, while no activity could be detected with benzoylformate. The enzyme shows pronounced substrate activation with indole-3-pyruvate and some other aromatic substrates, while for phenylpyruvate it appears to obey classical Michaelis-Menten kinetics. Based on these data, we propose a reclassification of the ipdC gene product of A. brasilense as a phenylpyruvate decarboxylase (EC 4.1.1.43).
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Affiliation(s)
- Stijn Spaepen
- Centre of Microbial and Plant Genetics, K.U. Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
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