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Garai S, Bhowal B, Gupta M, Sopory SK, Singla-Pareek SL, Pareek A, Kaur C. Role of methylglyoxal and redox homeostasis in microbe-mediated stress mitigation in plants. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2024; 338:111922. [PMID: 37952767 DOI: 10.1016/j.plantsci.2023.111922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 10/04/2023] [Accepted: 11/07/2023] [Indexed: 11/14/2023]
Abstract
One of the general consequences of stress in plants is the accumulation of reactive oxygen (ROS) and carbonyl species (like methylglyoxal) to levels that are detrimental for plant growth. These reactive species are inherently produced in all organisms and serve different physiological functions but their excessive accumulation results in cellular toxicity. It is, therefore, essential to restore equilibrium between their synthesis and breakdown to ensure normal cellular functioning. Detoxification mechanisms that scavenge these reactive species are considered important for stress mitigation as they maintain redox balance by restricting the levels of ROS, methylglyoxal and other reactive species in the cellular milieu. Stress tolerance imparted to plants by root-associated microbes involves a multitude of mechanisms, including maintenance of redox homeostasis. By improving the overall antioxidant response in plants, microbes can strengthen defense pathways and hence, the adaptive abilities of plants to sustain growth under stress. Hence, through this review we wish to highlight the contribution of root microbiota in modulating the levels of reactive species and thereby, maintaining redox homeostasis in plants as one of the important mechanisms of stress alleviation. Further, we also examine the microbial mechanisms of resistance to oxidative stress and their role in combating plant stress.
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Affiliation(s)
- Sampurna Garai
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Bidisha Bhowal
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Mayank Gupta
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sudhir K Sopory
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sneh L Singla-Pareek
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Ashwani Pareek
- National Agri-Food Biotechnology Institute, SAS Nagar, Mohali, Punjab 140306, India
| | - Charanpreet Kaur
- National Agri-Food Biotechnology Institute, SAS Nagar, Mohali, Punjab 140306, India.
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2
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Dunn MF, Becerra-Rivera VA. The Biosynthesis and Functions of Polyamines in the Interaction of Plant Growth-Promoting Rhizobacteria with Plants. PLANTS (BASEL, SWITZERLAND) 2023; 12:2671. [PMID: 37514285 PMCID: PMC10385936 DOI: 10.3390/plants12142671] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 07/12/2023] [Accepted: 07/15/2023] [Indexed: 07/30/2023]
Abstract
Plant growth-promoting rhizobacteria (PGPR) are members of the plant rhizomicrobiome that enhance plant growth and stress resistance by increasing nutrient availability to the plant, producing phytohormones or other secondary metabolites, stimulating plant defense responses against abiotic stresses and pathogens, or fixing nitrogen. The use of PGPR to increase crop yield with minimal environmental impact is a sustainable and readily applicable replacement for a portion of chemical fertilizer and pesticides required for the growth of high-yielding varieties. Increased plant health and productivity have long been gained by applying PGPR as commercial inoculants to crops, although with uneven results. The establishment of plant-PGPR relationships requires the exchange of chemical signals and nutrients between the partners, and polyamines (PAs) are an important class of compounds that act as physiological effectors and signal molecules in plant-microbe interactions. In this review, we focus on the role of PAs in interactions between PGPR and plants. We describe the basic ecology of PGPR and the production and function of PAs in them and the plants with which they interact. We examine the metabolism and the roles of PAs in PGPR and plants individually and during their interaction with one another. Lastly, we describe some directions for future research.
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Affiliation(s)
- Michael F Dunn
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico
| | - Víctor A Becerra-Rivera
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico
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3
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Minguillón S, Matamoros MA, Duanmu D, Becana M. Signaling by reactive molecules and antioxidants in legume nodules. THE NEW PHYTOLOGIST 2022; 236:815-832. [PMID: 35975700 PMCID: PMC9826421 DOI: 10.1111/nph.18434] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
Legume nodules are symbiotic structures formed as a result of the interaction with rhizobia. Nodules fix atmospheric nitrogen into ammonia that is assimilated by the plant and this process requires strict metabolic regulation and signaling. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are involved as signal molecules at all stages of symbiosis, from rhizobial infection to nodule senescence. Also, reactive sulfur species (RSS) are emerging as important signals for an efficient symbiosis. Homeostasis of reactive molecules is mainly accomplished by antioxidant enzymes and metabolites and is essential to allow redox signaling while preventing oxidative damage. Here, we examine the metabolic pathways of reactive molecules and antioxidants with an emphasis on their functions in signaling and protection of symbiosis. In addition to providing an update of recent findings while paying tribute to original studies, we identify several key questions. These include the need of new methodologies to detect and quantify ROS, RNS, and RSS, avoiding potential artifacts due to their short lifetimes and tissue manipulation; the regulation of redox-active proteins by post-translational modification; the production and exchange of reactive molecules in plastids, peroxisomes, nuclei, and bacteroids; and the unknown but expected crosstalk between ROS, RNS, and RSS in nodules.
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Affiliation(s)
- Samuel Minguillón
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
| | - Manuel A. Matamoros
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
| | - Deqiang Duanmu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and TechnologyHuazhong Agricultural UniversityWuhan430070China
| | - Manuel Becana
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
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Mandon K, Nazaret F, Farajzadeh D, Alloing G, Frendo P. Redox Regulation in Diazotrophic Bacteria in Interaction with Plants. Antioxidants (Basel) 2021; 10:antiox10060880. [PMID: 34070926 PMCID: PMC8226930 DOI: 10.3390/antiox10060880] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 05/26/2021] [Accepted: 05/26/2021] [Indexed: 11/23/2022] Open
Abstract
Plants interact with a large number of microorganisms that greatly influence their growth and health. Among the beneficial microorganisms, rhizosphere bacteria known as Plant Growth Promoting Bacteria increase plant fitness by producing compounds such as phytohormones or by carrying out symbioses that enhance nutrient acquisition. Nitrogen-fixing bacteria, either as endophytes or as endosymbionts, specifically improve the growth and development of plants by supplying them with nitrogen, a key macro-element. Survival and proliferation of these bacteria require their adaptation to the rhizosphere and host plant, which are particular ecological environments. This adaptation highly depends on bacteria response to the Reactive Oxygen Species (ROS), associated to abiotic stresses or produced by host plants, which determine the outcome of the plant-bacteria interaction. This paper reviews the different antioxidant defense mechanisms identified in diazotrophic bacteria, focusing on their involvement in coping with the changing conditions encountered during interaction with plant partners.
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Affiliation(s)
- Karine Mandon
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (K.M.); (F.N.); (G.A.)
| | - Fanny Nazaret
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (K.M.); (F.N.); (G.A.)
| | - Davoud Farajzadeh
- Department of Biology, Faculty of Basic Sciences, Azarbaijan Shahid Madani University, Tabriz 5375171379, Iran;
- Center for International Scientific Studies and Collaboration (CISSC), Ministry of Science, Research and Technology, Tehran 158757788, Iran
| | - Geneviève Alloing
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (K.M.); (F.N.); (G.A.)
| | - Pierre Frendo
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (K.M.); (F.N.); (G.A.)
- Correspondence:
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Ledermann R, Emmenegger B, Couzigou JM, Zamboni N, Kiefer P, Vorholt JA, Fischer HM. Bradyrhizobium diazoefficiens Requires Chemical Chaperones To Cope with Osmotic Stress during Soybean Infection. mBio 2021; 12:e00390-21. [PMID: 33785618 PMCID: PMC8092242 DOI: 10.1128/mbio.00390-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 01/24/2023] Open
Abstract
When engaging in symbiosis with legume hosts, rhizobia are confronted with environmental changes, including nutrient availability and stress exposure. Genetic circuits allow responding to these environmental stimuli to optimize physiological adaptations during the switch from the free-living to the symbiotic life style. A pivotal regulatory system of the nitrogen-fixing soybean endosymbiont Bradyrhizobium diazoefficiens for efficient symbiosis is the general stress response (GSR), which relies on the alternative sigma factor σEcfG However, the GSR-controlled process required for symbiosis has not been identified. Here, we demonstrate that biosynthesis of trehalose is under GSR control, and mutants lacking the respective biosynthetic genes otsA and/or otsB phenocopy GSR-deficient mutants under symbiotic and selected free-living stress conditions. The role of trehalose as a cytoplasmic chemical chaperone and stress protectant can be functionally replaced in an otsA or otsB mutant by introducing heterologous genetic pathways for biosynthesis of the chemically unrelated compatible solutes glycine betaine and (hydroxy)ectoine. Alternatively, uptake of exogenously provided trehalose also restores efficient symbiosis and tolerance to hyperosmotic and hyperionic stress of otsA mutants. Hence, elevated cytoplasmic trehalose levels resulting from GSR-controlled biosynthesis are crucial for B. diazoefficiens cells to overcome adverse conditions during early stages of host infection and ensure synchronization with root nodule development.IMPORTANCE The Bradyrhizobium-soybean symbiosis is of great agricultural significance and serves as a model system for fundamental research in bacterium-plant interactions. While detailed molecular insight is available about mutual recognition and early nodule organogenesis, our understanding of the host-imposed conditions and the physiology of infecting rhizobia during the transition from a free-living state in the rhizosphere to endosymbiotic bacteroids is currently limited. In this study, we show that the requirement of the rhizobial general stress response (GSR) during host infection is attributable to GSR-controlled biosynthesis of trehalose. Specifically, trehalose is crucial for an efficient symbiosis by acting as a chemical chaperone to protect rhizobia from osmostress during host infection.
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Affiliation(s)
| | | | | | - Nicola Zamboni
- ETH Zurich, Institute of Molecular Systems Biology, Zurich, Switzerland
| | - Patrick Kiefer
- ETH Zurich, Institute of Microbiology, Zurich, Switzerland
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Lu C, Yang Z, Liu J, Liao Q, Ling W, Waigi MG, Odinga ES. Chlorpyrifos inhibits nitrogen fixation in rice-vegetated soil containing Pseudomonas stutzeri A1501. CHEMOSPHERE 2020; 256:127098. [PMID: 32470732 DOI: 10.1016/j.chemosphere.2020.127098] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/30/2020] [Accepted: 05/14/2020] [Indexed: 05/28/2023]
Abstract
Chlorpyrifos, a common organophosphorus pesticide, is widely used for agricultural pest control and can inhibit nitrogen-fixing bacteria biomass in paddy. In this study, the additions of chlorpyrifos (1 and 8 mg kg-1) to soil, with or without Pseudomonas stutzeri A1501, resulted in a significant decrease in nitrogen fixation, despite insignificant effects on the abundances of P. stutzeri A1501 and bacteria in soil. Toxic effect of chlorpyrifos on P. stutzeri A1501 nitrogenase activity in medium was also observed, accompanied by a significant reduction in the expression of nitrogen-fixing related genes (nifA and nifH). Furthermore, rhizosphere colonization and biofilm formation by P. stutzeri A1501 were repressed by chlorpyrifos, leading to decreased nitrogenase activity in the rhizosphere. Biofilm formation in medium was inhibited by bacterial hyperkinesis and reduction of extracellular polymeric substance, including exopolysaccharides and proteins. Together, these findings showed that chlorpyrifos-induced production of reactive oxygen species (ROS) which was directly responsible for reduced nitrogenase activity in the medium, soil, and rhizosphere by inhibiting the expressions of nitrogen-fixing related genes. Furthermore, the inhibition of biofilm formation by chlorpyrifos or ROS likely aggravated the reduction in rhizospherere nitrogenase activity. These findings provide potentially valuable insights into the toxicity of chlorpyrifos on nitrogen-fixing bacteria and its mechanisms. Furthermore, for sustainable rice production, it is necessary to evaluate whether other pesticides affect nitrogen fixation and select pesticides that do not inhibit nitrogen fixation.
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Affiliation(s)
- Chao Lu
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Zhimin Yang
- National Key Facility for Crop Gene Resources and Genetic Improvement, Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Juan Liu
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Qihang Liao
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Wanting Ling
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
| | - Michael Gatheru Waigi
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Emmanuel Stephen Odinga
- Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
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7
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Demtröder L, Pfänder Y, Schäkermann S, Bandow JE, Masepohl B. NifA is the master regulator of both nitrogenase systems in Rhodobacter capsulatus. Microbiologyopen 2019; 8:e921. [PMID: 31441241 PMCID: PMC6925177 DOI: 10.1002/mbo3.921] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 07/16/2019] [Accepted: 07/18/2019] [Indexed: 01/09/2023] Open
Abstract
Rhodobacter capsulatus fixes atmospheric nitrogen (N2) by a molybdenum (Mo)‐nitrogenase and a Mo‐free iron (Fe)‐nitrogenase, whose production is induced or repressed by Mo, respectively. At low nanomolar Mo concentrations, both isoenzymes are synthesized and contribute to nitrogen fixation. Here we examined the regulatory interplay of the central transcriptional activators NifA and AnfA by proteome profiling. As expected from earlier studies, synthesis of the structural proteins of Mo‐nitrogenase (NifHDK) and Fe‐nitrogenase (AnfHDGK) required NifA and AnfA, respectively, both of which depend on the alternative sigma factor RpoN to activate expression of their target genes. Unexpectedly, NifA was found to be essential for the synthesis of Fe‐nitrogenase, electron supply to both nitrogenases, biosynthesis of their cofactors, and production of RpoN. Apparently, RpoN is the only NifA‐dependent factor required for target gene activation by AnfA, since plasmid‐borne rpoN restored anfH transcription in a NifA‐deficient strain. However, plasmid‐borne rpoN did not restore Fe‐nitrogenase activity in this strain. Taken together, NifA requirement for synthesis and activity of both nitrogenases suggests that Fe‐nitrogenase functions as a complementary nitrogenase rather than an alternative isoenzyme in R. capsulatus.
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Affiliation(s)
- Lisa Demtröder
- Microbial Biology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Yvonne Pfänder
- Microbial Biology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Sina Schäkermann
- Applied Microbiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Julia Elisabeth Bandow
- Applied Microbiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Bernd Masepohl
- Microbial Biology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
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8
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Wang S, Lu T, Xue Q, Xu K, Cheng G. Antioxidation and symbiotic nitrogen fixation function of prxA gene in Mesorhizobium huakuii. Microbiologyopen 2019; 8:e889. [PMID: 31177643 PMCID: PMC6813433 DOI: 10.1002/mbo3.889] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 05/20/2019] [Accepted: 05/20/2019] [Indexed: 02/06/2023] Open
Abstract
Peroxiredoxins (Prxs) play an essential role in the antioxidant activity and symbiotic capacity of Mesorhizobium huakuii. A mutation in the M. huakuii prxA gene (encoding a Prx5‐like peroxiredoxin) was generated by homologous recombination. The mutation of prxA did not affect M. huakuii growth, but the strain displayed decreased antioxidative capacity under organic cumene hydroperoxide (CUOOH) conditions. The higher resistance of the prxA mutant strain compared with the wild‐type strain to more than 1 mmol/L H2O2 was associated with a significantly higher level of glutathione reductase activity and a significantly lower level of intracellular hydrogen peroxide content. Real‐time quantitative PCR showed that under 1 mmol/L H2O2 conditions, expression of the stress‐responsive genes katG and katE was significantly upregulated in the prxA mutant. Although the prxA mutant can form nodules, the symbiotic ability was severely impaired, which led to an abnormal nodulation phenotype coupled to a 53.25% reduction in nitrogen fixation capacity. This phenotype was linked to an absence of bacteroid differentiation and deregulation of the transcription of the symbiotic genes nifH, nifD, and fdxN. Expression of the prxA gene was induced during symbiosis. Thus, the PrxA protein is essential for antioxidant capacity and symbiotic nitrogen fixation, playing independent roles in bacterial differentiation and cellular antioxidative systems.
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Affiliation(s)
- Sanjiao Wang
- College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China
| | - Tiantian Lu
- College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China
| | - Qiang Xue
- College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China
| | - Ke Xu
- College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China
| | - Guojun Cheng
- College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China.,Hubei Provincial Engineering and Technology Research Center for Resources and Utilization of Microbiology, College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China
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9
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Taboada H, Dunn MF, Meneses N, Vargas-Lagunas C, Buchs N, Andrade-Domínguez A, Encarnación S. Qualitative changes in proteins contained in outer membrane vesicles produced by Rhizobium etli grown in the presence of the nod gene inducer naringenin. Arch Microbiol 2019; 201:1173-1194. [DOI: 10.1007/s00203-019-01682-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 04/22/2019] [Accepted: 05/21/2019] [Indexed: 02/07/2023]
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Alloing G, Mandon K, Boncompagni E, Montrichard F, Frendo P. Involvement of Glutaredoxin and Thioredoxin Systems in the Nitrogen-Fixing Symbiosis between Legumes and Rhizobia. Antioxidants (Basel) 2018; 7:E182. [PMID: 30563061 PMCID: PMC6315971 DOI: 10.3390/antiox7120182] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 11/30/2018] [Accepted: 12/01/2018] [Indexed: 01/08/2023] Open
Abstract
Leguminous plants can form a symbiotic relationship with Rhizobium bacteria, during which plants provide bacteria with carbohydrates and an environment appropriate to their metabolism, in return for fixed atmospheric nitrogen. The symbiotic interaction leads to the formation of a new organ, the root nodule, where a coordinated differentiation of plant cells and bacteria occurs. The establishment and functioning of nitrogen-fixing symbiosis involves a redox control important for both the plant-bacteria crosstalk and the regulation of nodule metabolism. In this review, we discuss the involvement of thioredoxin and glutaredoxin systems in the two symbiotic partners during symbiosis. The crucial role of glutathione in redox balance and S-metabolism is presented. We also highlight the specific role of some thioredoxin and glutaredoxin systems in bacterial differentiation. Transcriptomics data concerning genes encoding components and targets of thioredoxin and glutaredoxin systems in connection with the developmental step of the nodule are also considered in the model system Medicago truncatula⁻Sinorhizobium meliloti.
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Affiliation(s)
| | | | | | - Françoise Montrichard
- IRHS, INRA, AGROCAMPUS-Ouest, Université d'Angers, SFR 4207 QUASAV, 42 rue Georges Morel, 49071 Beaucouzé CEDEX, France.
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11
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Catalase Expression in Azospirillum brasilense Sp7 Is Regulated by a Network Consisting of OxyR and Two RpoH Paralogs and Including an RpoE1→RpoH5 Regulatory Cascade. Appl Environ Microbiol 2018; 84:AEM.01787-18. [PMID: 30217849 DOI: 10.1128/aem.01787-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 09/01/2018] [Indexed: 12/19/2022] Open
Abstract
The genome of Azospirillum brasilense encodes five RpoH sigma factors: two OxyR transcription regulators and three catalases. The aim of this study was to understand the role they play during oxidative stress and their regulatory interconnection. Out of the 5 paralogs of RpoH present in A. brasilense, inactivation of only rpoH1 renders A. brasilense heat sensitive. While transcript levels of rpoH1 were elevated by heat stress, those of rpoH3 and rpoH5 were upregulated by H2O2 Catalase activity was upregulated in A. brasilense and its rpoH::km mutants in response to H2O2 except in the case of the rpoH5::km mutant, suggesting a role for RpoH5 in regulating inducible catalase. Transcriptional analysis of the katN, katAI, and katAII genes revealed that the expression of katN and katAII was severely compromised in the rpoH3::km and rpoH5::km mutants, respectively. Regulation of katN and katAII by RpoH3 and RpoH5, respectively, was further confirmed in an Escherichia coli two-plasmid system. Regulation of katAII by OxyR2 was evident by a drastic reduction in growth, KatAII activity, and katAII::lacZ expression in an oxyR2::km mutant. This study reports the involvement of RpoH3 and RpoH5 sigma factors in regulating oxidative stress response in alphaproteobacteria. We also report the regulation of an inducible catalase by a cascade of alternative sigma factors and an OxyR. Out of the three catalases in A. brasilense, those corresponding to katN and katAII are regulated by RpoH3 and RpoH5, respectively. The expression of katAII is regulated by a cascade of RpoE1→RpoH5 and OxyR2.IMPORTANCE In silico analysis of the A. brasilense genome showed the presence of multiple paralogs of genes involved in oxidative stress response, which included 2 OxyR transcription regulators and 3 catalases. So far, Deinococcus radiodurans and Vibrio cholerae are known to harbor two paralogs of OxyR, and Sinorhizobium meliloti harbors three catalases. We do not yet know how the expression of multiple catalases is regulated in any bacterium. Here we show the role of multiple RpoH sigma factors and OxyR in regulating the expression of multiple catalases in A. brasilense Sp7. Our work gives a glimpse of systems biology of A. brasilense used for responding to oxidative stress.
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12
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Ormeño-Orrillo E, Gomes DF, Del Cerro P, Vasconcelos ATR, Canchaya C, Almeida LGP, Mercante FM, Ollero FJ, Megías M, Hungria M. Genome of Rhizobium leucaenae strains CFN 299(T) and CPAO 29.8: searching for genes related to a successful symbiotic performance under stressful conditions. BMC Genomics 2016; 17:534. [PMID: 27485828 PMCID: PMC4971678 DOI: 10.1186/s12864-016-2859-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Accepted: 06/27/2016] [Indexed: 01/02/2023] Open
Abstract
Background Common bean (Phaseolus vulgaris L.) is the most important legume cropped worldwide for food production and its agronomic performance can be greatly improved if the benefits from symbiotic nitrogen fixation are maximized. The legume is known for its high promiscuity in nodulating with several Rhizobium species, but those belonging to the Rhizobium tropici “group” are the most successful and efficient in fixing nitrogen in tropical acid soils. Rhizobium leucaenae belongs to this group, which is abundant in the Brazilian “Cerrados” soils and frequently submitted to several environmental stresses. Here we present the first high-quality genome drafts of R. leucaenae, including the type strain CFN 299T and the very efficient strain CPAO 29.8. Our main objective was to identify features that explain the successful capacity of R. leucaenae in nodulating common bean under stressful environmental conditions. Results The genomes of R. leucaenae strains CFN 299T and CPAO 29.8 were estimated at 6.7–6.8 Mbp; 7015 and 6899 coding sequences (CDS) were predicted, respectively, 6264 of which are common to both strains. The genomes of both strains present a large number of CDS that may confer tolerance of high temperatures, acid soils, salinity and water deficiency. Types I, II, IV-pili, IV and V secretion systems were present in both strains and might help soil and host colonization as well as the symbiotic performance under stressful conditions. The symbiotic plasmid of CPAO 29.8 is highly similar to already described tropici pSyms, including five copies of nodD and three of nodA genes. R. leucaenae CFN 299T is capable of synthesizing Nod factors in the absence of flavonoids when submitted to osmotic stress, indicating that under abiotic stress the regulation of nod genes might be different. Conclusion A detailed study of the genes putatively related to stress tolerance in R. leucaenae highlighted an intricate pattern comprising a variety of mechanisms that are probably orchestrated to tolerate the stressful conditions to which the strains are submitted on a daily basis. The capacity to synthesize Nod factors under abiotic stress might follow the same regulatory pathways as in CIAT 899T and may help both to improve bacterial survival and to expand host range to guarantee the perpetuation of the symbiosis. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2859-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Douglas Fabiano Gomes
- Embrapa Soja, C.P. 231, 86001-970, Londrina, Paraná, Brazil.,CAPES, SBN, Quadra 2, Bloco L, Lote 06, Edifício Capes, 70.040-020, Brasília, Federal District, Brazil
| | - Pablo Del Cerro
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal, 41012, Sevilla, Spain
| | - Ana Tereza Ribeiro Vasconcelos
- Laboratório Nacional de Computação Científica (LNCC), Labinfo, Rua Getúlio Vargas 333, 25651-071, Petrópolis, Rio de Janeiro, Brazil
| | - Carlos Canchaya
- Department Biochemistry, Genetics and Immunology, Faculty of Biology, University of Vigo, 36310, Vigo, Spain
| | - Luiz Gonzaga Paula Almeida
- Laboratório Nacional de Computação Científica (LNCC), Labinfo, Rua Getúlio Vargas 333, 25651-071, Petrópolis, Rio de Janeiro, Brazil
| | | | - Francisco Javier Ollero
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal, 41012, Sevilla, Spain
| | - Manuel Megías
- Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes, 6 Apdo Postal, 41012, Sevilla, Spain
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Muñoz V, Ibáñez F, Figueredo MS, Fabra A. An oxidative burst and its attenuation by bacterial peroxidase activity is required for optimal establishment of the Arachis hypogaea-Bradyrhizobium sp. symbiosis. J Appl Microbiol 2016; 121:244-53. [PMID: 27037857 DOI: 10.1111/jam.13149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/26/2016] [Accepted: 03/29/2016] [Indexed: 12/13/2022]
Abstract
AIMS The main purpose of this study was to determine whether the Arachis hypogaea L. root oxidative burst, produced at early stages of its symbiotic interaction with Bradyrhizobium sp. SEMIA 6144, and the bacterial antioxidant system are required for the successful development of this interaction. METHODS AND RESULTS Pharmacological approaches were used to reduce both plant oxidative burst and bacterial peroxidase enzyme activity. In plants whose H2 O2 levels were decreased, a low nodule number, a reduction in the proportion of red nodules (%) and an increase in the bacteroid density were found. The symbiotic phenotype of plants inoculated with a Bradyrhizobium sp. SEMIA 6144 culture showing decreased peroxidase activity was also affected, since the biomass production, nodule number and percentage of red nodules in these plants were lower than in plants inoculated with Bradyrhizobium sp. control cultures. CONCLUSIONS We demonstrated for the first time that the oxidative burst triggered at the early events of the symbiotic interaction in peanut, is a prerequisite for the efficient development of root nodules, and that the antioxidant system of bradyrhizobial peanut symbionts, particularly the activity of peroxidases, is counteracting this oxidative burst for the successful establishment of the symbiosis. SIGNIFICANCE AND IMPACT OF THE STUDY Our results provide new insights into the mechanisms involved in the development of the symbiotic interaction established in A. hypogaea L. a legume infected in an intercellular way.
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Affiliation(s)
- V Muñoz
- Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina
| | - F Ibáñez
- Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina
| | - M S Figueredo
- Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina
| | - A Fabra
- Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina
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14
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Zhao Y, Nickels LM, Wang H, Ling J, Zhong Z, Zhu J. OxyR-regulated catalase activity is critical for oxidative stress resistance, nodulation and nitrogen fixation in Azorhizobium caulinodans. FEMS Microbiol Lett 2016; 363:fnw130. [PMID: 27190162 DOI: 10.1093/femsle/fnw130] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/12/2016] [Indexed: 11/13/2022] Open
Abstract
The legume-rhizobial interaction results in the formation of symbiotic nodules in which rhizobia fix nitrogen. During the process of symbiosis, reactive oxygen species (ROS) are generated. Thus, the response of rhizobia to ROS is important for successful nodulation and nitrogen fixation. In this study, we investigated how Azorhizobium caulinodans, a rhizobium that forms both root and stem nodules on its host plant, regulates ROS resistance. We found that in-frame deletions of a gene encoding the putative catalase-peroxidase katG or a gene encoding a LysR-family regulatory protein, oxyR, exhibited increased sensitivity to H2O2 We then showed that OxyR positively regulated katG expression in an H2O2-independent fashion. Furthermore, we found that deletion of katG or oxyR led to significant reduction in the number of stem nodules and decrease of nitrogen fixation capacities in symbiosis. Our results revealed that KatG and OxyR are not only critical for antioxidant defense in vitro, but also important for nodule formation and nitrogen fixation during interaction with plant hosts.
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Affiliation(s)
- Yue Zhao
- Department of Microbiology, College of Biological Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China 210095
| | - Logan M Nickels
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hui Wang
- Department of Microbiology, College of Biological Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China 210095
| | - Jun Ling
- Department of Microbiology, College of Biological Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China 210095
| | - Zengtao Zhong
- Department of Microbiology, College of Biological Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China 210095
| | - Jun Zhu
- Department of Microbiology, College of Biological Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China 210095 Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104, USA
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Hu J, Akula N, Wang N. Development of a Microemulsion Formulation for Antimicrobial SecA Inhibitors. PLoS One 2016; 11:e0150433. [PMID: 26963811 PMCID: PMC4786163 DOI: 10.1371/journal.pone.0150433] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 02/13/2016] [Indexed: 11/19/2022] Open
Abstract
In our previous study, we have identified five antimicrobial small molecules via structure based design, which inhibit SecA of Candidatus Liberibacter asiaticus (Las). SecA is a critical protein translocase ATPase subunit and is involved in pre-protein translocation across and integration into the cellular membrane in bacteria. In this study, eleven compounds were identified using similarity search method based on the five lead SecA inhibitors identified previously. The identified SecA inhibitors have poor aqueous solubility. Thus a microemulsion master mix (MMX) was developed to address the solubility issue and for application of the antimicrobials. MMX consists of N-methyl-2-pyrrolidone and dimethyl sulfoxide as solvent and co-solvent, as well as polyoxyethylated castor oil, polyalkylene glycol, and polyoxyethylene tridecyl ether phosphate as surfactants. MMX has significantly improved the solubility of SecA inhibitors and has no or little phytotoxic effects at concentrations less than 5.0% (v/v). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the SecA inhibitors and streptomycin against eight bacteria including Agrobacterium tumefaciens, Liberibacter crescens, Rhizobium etli, Bradyrhizobium japonicum, Mesorhizobium loti, and Sinorhizobium meliloti phylogenetically related to Las were determined using the broth microdilution method. MIC and MBC results showed that the 16 SecA inhibitors have antibacterial activities comparable to that of streptomycin. Overall, we have identified 11 potent SecA inhibitors using similarity search method. We have developed a microemulsion formulation for SecA inhibitors which improved the antimicrobial activities of SecA inhibitors.
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Affiliation(s)
- Jiahuai Hu
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
| | - Nagaraju Akula
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
| | - Nian Wang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, Florida, United States of America
- * E-mail:
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16
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Zhang H, Ni Z, Chen Q, Guo Z, Gao W, Su X, Qu Y. Proteomic responses of drought-tolerant and drought-sensitive cotton varieties to drought stress. Mol Genet Genomics 2016; 291:1293-303. [PMID: 26941218 DOI: 10.1007/s00438-016-1188-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 02/24/2016] [Indexed: 12/27/2022]
Abstract
Drought, one of the most widespread factors reducing agricultural crop productivity, affects biological processes such as development, architecture, flowering and senescence. Although protein analysis techniques and genome sequencing have made facilitated the proteomic study of cotton, information on genetic differences associated with proteomic changes in response to drought between different cotton genotypes is lacking. To determine the effects of drought stress on cotton seedlings, we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry to comparatively analyze proteome of drought-responsive proteins during the seedling stage in two cotton (Gossypium hirsutum L.) cultivars, drought-tolerant KK1543 and drought-sensitive Xinluzao26. A total of 110 protein spots were detected on 2-DE maps, of which 56 were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry. The identified proteins were mainly associated with metabolism (46.4 %), antioxidants (14.2 %), and transport and cellular structure (23.2 %). Some key proteins had significantly different expression patterns between the two genotypes. In particular, 5-methyltetrahydropteroyltriglutamate-homocysteine methyltransferase, UDP-D-glucose pyrophosphorylase and ascorbate peroxidase were up-regulated in KK1543 compared with Xinluzao26. Under drought stress conditions, the vacuolar H(+)-ATPase catalytic subunit, a 14-3-3g protein, translation initiation factor 5A and pathogenesis-related protein 10 were up-regulated in KK1543, whereas ribosomal protein S12, actin, cytosolic copper/zinc superoxide dismutase, protein disulfide isomerase, S-adenosylmethionine synthase and cysteine synthase were down-regulated in Xinluzao26. This work represents the first characterization of proteomic changes that occur in response to drought in roots of cotton plants. These differentially expressed proteins may be related to biochemical pathways responsible for drought tolerance in KK1543. Although further studies are needed, this proteomic analysis underlines the role of post-translational events. The differentially expressed proteins and their corresponding genes may be used as markers for the breeding of drought tolerance in cotton.
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Affiliation(s)
- Haiyan Zhang
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Zhiyong Ni
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Quanjia Chen
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Zhongjun Guo
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Wenwei Gao
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Xiujuan Su
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China
| | - Yanying Qu
- College of Agronomy, Xinjiang Agricultural University, Urumqi, 830052, China.
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Ribeiro CW, Alloing G, Mandon K, Frendo P. Redox regulation of differentiation in symbiotic nitrogen fixation. Biochim Biophys Acta Gen Subj 2014; 1850:1469-78. [PMID: 25433163 DOI: 10.1016/j.bbagen.2014.11.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 10/30/2014] [Accepted: 11/18/2014] [Indexed: 12/22/2022]
Abstract
BACKGROUND Nitrogen-fixing symbiosis between Rhizobium bacteria and legumes leads to the formation of a new organ, the root nodule. The development of the nodule requires the differentiation of plant root cells to welcome the endosymbiotic bacterial partner. This development includes the formation of an efficient vascular tissue which allows metabolic exchanges between the root and the nodule, the formation of a barrier to oxygen diffusion necessary for the bacterial nitrogenase activity and the enlargement of cells in the infection zone to support the large bacterial population. Inside the plant cell, the bacteria differentiate into bacteroids which are able to reduce atmospheric nitrogen to ammonia needed for plant growth in exchange for carbon sources. Nodule functioning requires a tight regulation of the development of plant cells and bacteria. SCOPE OF THE REVIEW Nodule functioning requires a tight regulation of the development of plant cells and bacteria. The importance of redox control in nodule development and N-fixation is discussed in this review. The involvement of reactive oxygen and nitrogen species and the importance of the antioxidant defense are analyzed. MAJOR CONCLUSIONS Plant differentiation and bacterial differentiation are controlled by reactive oxygen and nitrogen species, enzymes involved in the antioxidant defense and antioxidant compounds. GENERAL SIGNIFICANCE The establishment and functioning of nitrogen-fixing symbiosis involve a redox control important for both the plant-bacteria crosstalk and the consideration of environmental parameters. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.
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Affiliation(s)
- Carolina Werner Ribeiro
- Institut Sophia Agrobiotech, Université de Nice-Sophia Antipolis, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, INRA UMR 1355, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, CNRS UMR 7254, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France
| | - Geneviève Alloing
- Institut Sophia Agrobiotech, Université de Nice-Sophia Antipolis, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, INRA UMR 1355, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, CNRS UMR 7254, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France
| | - Karine Mandon
- Institut Sophia Agrobiotech, Université de Nice-Sophia Antipolis, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, INRA UMR 1355, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, CNRS UMR 7254, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France
| | - Pierre Frendo
- Institut Sophia Agrobiotech, Université de Nice-Sophia Antipolis, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, INRA UMR 1355, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France; Institut Sophia Agrobiotech, CNRS UMR 7254, 400 Route des Chappes, BP167, F-06903 Sophia Antipolis Cedex, France.
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18
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Sarkar A, Reinhold-Hurek B. Transcriptional profiling of nitrogen fixation and the role of NifA in the diazotrophic endophyte Azoarcus sp. strain BH72. PLoS One 2014; 9:e86527. [PMID: 24516534 PMCID: PMC3916325 DOI: 10.1371/journal.pone.0086527] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/09/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The model endophyte Azoarcus sp. strain BH72 is known to contribute fixed nitrogen to its host Kallar grass and also expresses nitrogenase genes endophytically in rice seedlings. Availability of nitrogen is a signal regulating the transcription of nitrogenase genes. Therefore, we analysed global transcription in response to differences in the nitrogen source. METHODOLOGY/PRINCIPAL FINDINGS A DNA microarray, comprising 70-mer oligonucleotides representing 3989 open reading frames of the genome of strain BH72, was used for transcriptome studies. Transcription profiles of cells grown microaerobically on N2 versus ammonium were compared. Expression of 7.2% of the genes was significantly up-regulated, and 5.8% down-regulated upon N2 fixation, respectively. A parallel genome-wide prediction of σ(54)-type promoter elements mapped to the upstream region of 38 sequences of which 36 were modulated under the N2 response. In addition to modulation of genes related to N2 fixation, the expressions of gene clusters that might be related to plant-microbe interaction and of several transcription factors were significantly enhanced. While comparing under N2-fixation conditions the transcriptome of wild type with a nifLA(-) insertion mutant, NifA being the essential transcriptional activator for nif genes, 24.5% of the genome was found to be affected in expression. A genome-wide prediction of 29 NifA binding sequences matched to 25 of the target genes whose expression was differential during microarray analysis, some of which were putatively negatively regulated by NifA. For selected genes, differential expression was corroborated by real time RT-PCR studies. CONCLUSION/SIGNIFICANCE Our data suggest that life under conditions of nitrogen fixation is an important part of the lifestyle of strain BH72 in roots, as a wide range of genes far beyond the nif regulon is modulated. Moreover, the NifA regulon in strain BH72 appears to encompass a wider range of cellular functions beyond the regulation of nif genes.
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Affiliation(s)
- Abhijit Sarkar
- University of Bremen, Faculty of Biology, Department of Microbe-Plant Interactions, Bremen, Germany
| | - Barbara Reinhold-Hurek
- University of Bremen, Faculty of Biology, Department of Microbe-Plant Interactions, Bremen, Germany
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19
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Ramírez M, Guillén G, Fuentes SI, Iñiguez LP, Aparicio-Fabre R, Zamorano-Sánchez D, Encarnación-Guevara S, Panzeri D, Castiglioni B, Cremonesi P, Strozzi F, Stella A, Girard L, Sparvoli F, Hernández G. Transcript profiling of common bean nodules subjected to oxidative stress. PHYSIOLOGIA PLANTARUM 2013; 149:389-407. [PMID: 23432573 DOI: 10.1111/ppl.12040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 01/25/2013] [Accepted: 01/28/2013] [Indexed: 06/01/2023]
Abstract
Several environmental stresses generate high amounts of reactive oxygen species (ROS) in plant cells, resulting in oxidative stress. Symbiotic nitrogen fixation (SNF) in the legume-rhizobia symbiosis is sensitive to damage from oxidative stress. Active nodules of the common bean (Phaseolus vulgaris) exposed to the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride hydrate), which stimulates ROS accumulation, exhibited reduced nitrogenase activity and ureide content. We analyzed the global gene response of nodules subjected to oxidative stress using the Bean Custom Array 90K, which includes probes from 30,000 expressed sequence tags (ESTs). A total of 4280 ESTs were differentially expressed in stressed bean nodules; of these, 2218 were repressed. Based on Gene Ontology analysis, these genes were grouped into 42 different biological process categories. Analysis with the PathExpress bioinformatic tool, adapted for bean, identified five significantly repressed metabolic pathways related to carbon/nitrogen metabolism, which is crucial for nodule function. Quantitative reverse transcription (qRT)-PCR analysis of transcription factor (TF) gene expression showed that 67 TF genes were differentially expressed in nodules exposed to oxidative stress. Putative cis-elements recognized by highly responsive TF were detected in promoter regions of oxidative stress regulated genes. The expression of oxidative stress responsive genes and of genes important for SNF in bacteroids analyzed in stressed nodules revealed that these conditions elicited a transcriptional response.
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Affiliation(s)
- Mario Ramírez
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Av. Universidad 1001, Cuernavaca, Mor. 62209, Mexico
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20
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Jans A, Vercruysse M, Gao S, Engelen K, Lambrichts I, Fauvart M, Michiels J. Canonical and non-canonical EcfG sigma factors control the general stress response in Rhizobium etli. Microbiologyopen 2013; 2:976-87. [PMID: 24311555 PMCID: PMC3892343 DOI: 10.1002/mbo3.137] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Revised: 09/16/2013] [Accepted: 09/23/2013] [Indexed: 01/14/2023] Open
Abstract
A core component of the α-proteobacterial general stress response (GSR) is the extracytoplasmic function (ECF) sigma factor EcfG, exclusively present in this taxonomic class. Half of the completed α-proteobacterial genome sequences contain two or more copies of genes encoding σEcfG-like sigma factors, with the primary copy typically located adjacent to genes coding for a cognate anti-sigma factor (NepR) and two-component response regulator (PhyR). So far, the widespread occurrence of additional, non-canonical σEcfG copies has not satisfactorily been explained. This study explores the hierarchical relation between Rhizobium etli σEcfG1 and σEcfG2, canonical and non-canonical σEcfG proteins, respectively. Contrary to reports in other species, we find that σEcfG1 and σEcfG2 act in parallel, as nodes of a complex regulatory network, rather than in series, as elements of a linear regulatory cascade. We demonstrate that both sigma factors control unique yet also shared target genes, corroborating phenotypic evidence. σEcfG1 drives expression of rpoH2, explaining the increased heat sensitivity of an ecfG1 mutant, while katG is under control of σEcfG2, accounting for reduced oxidative stress resistance of an ecfG2 mutant. We also identify non-coding RNA genes as novel σEcfG targets. We propose a modified model for GSR regulation in R. etli, in which σEcfG1 and σEcfG2 function largely independently. Based on a phylogenetic analysis and considering the prevalence of α-proteobacterial genomes with multiple σEcfG copies, this model may also be applicable to numerous other species.
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Affiliation(s)
- Ann Jans
- Centre of Microbial and Plant Genetics, KU Leuven, Heverlee, B-3001, Belgium
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21
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Frendo P, Matamoros MA, Alloing G, Becana M. Thiol-based redox signaling in the nitrogen-fixing symbiosis. FRONTIERS IN PLANT SCIENCE 2013; 4:376. [PMID: 24133498 PMCID: PMC3783977 DOI: 10.3389/fpls.2013.00376] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 09/03/2013] [Indexed: 05/04/2023]
Abstract
In nitrogen poor soils legumes establish a symbiotic interaction with rhizobia that results in the formation of root nodules. These are unique plant organs where bacteria differentiate into bacteroids, which express the nitrogenase enzyme complex that reduces atmospheric N 2 to ammonia. Nodule metabolism requires a tight control of the concentrations of reactive oxygen and nitrogen species (RONS) so that they can perform useful signaling roles while avoiding nitro-oxidative damage. In nodules a thiol-dependent regulatory network that senses, transmits and responds to redox changes is starting to be elucidated. A combination of enzymatic, immunological, pharmacological and molecular analyses has allowed us to conclude that glutathione and its legume-specific homolog, homoglutathione, are abundant in meristematic and infected cells, that their spatio-temporally distribution is correlated with the corresponding (homo)glutathione synthetase activities, and that they are crucial for nodule development and function. Glutathione is at high concentrations in the bacteroids and at moderate amounts in the mitochondria, cytosol and nuclei. Less information is available on other components of the network. The expression of multiple isoforms of glutathione peroxidases, peroxiredoxins, thioredoxins, glutaredoxins and NADPH-thioredoxin reductases has been detected in nodule cells using antibodies and proteomics. Peroxiredoxins and thioredoxins are essential to regulate and in some cases to detoxify RONS in nodules. Further research is necessary to clarify the regulation of the expression and activity of thiol redox-active proteins in response to abiotic, biotic and developmental cues, their interactions with downstream targets by disulfide-exchange reactions, and their participation in signaling cascades. The availability of mutants and transgenic lines will be crucial to facilitate systematic investigations into the function of the various proteins in the legume-rhizobial symbiosis.
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Affiliation(s)
- Pierre Frendo
- Institut Sophia Agrobiotech, Université de Nice-Sophia AntipolisNice, France
- Institut Sophia Agrobiotech, Institut National de la Recherche Agronomique, Unité Mixte de Recherches 1355Nice, France
- Institut Sophia Agrobiotech, Centre National de la Recherche Scientifique, Unité Mixte de Recherches 7254Nice, France
- Pierre Frendo and Manuel A. Matamoros have contributed equally to this review.
| | - Manuel A. Matamoros
- Estación Experimental de Aula Dei, Consejo Superior de Investigaciones CientíficasZaragoza, Spain
- Pierre Frendo and Manuel A. Matamoros have contributed equally to this review.
| | - Geneviève Alloing
- Institut Sophia Agrobiotech, Université de Nice-Sophia AntipolisNice, France
- Institut Sophia Agrobiotech, Institut National de la Recherche Agronomique, Unité Mixte de Recherches 1355Nice, France
- Institut Sophia Agrobiotech, Centre National de la Recherche Scientifique, Unité Mixte de Recherches 7254Nice, France
| | - Manuel Becana
- Estación Experimental de Aula Dei, Consejo Superior de Investigaciones CientíficasZaragoza, Spain
- *Correspondence: Manuel Becana, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, Apartado 13034, 50080 Zaragoza, Spain e-mail:
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Puppo A, Pauly N, Boscari A, Mandon K, Brouquisse R. Hydrogen peroxide and nitric oxide: key regulators of the Legume-Rhizobium and mycorrhizal symbioses. Antioxid Redox Signal 2013; 18:2202-19. [PMID: 23249379 DOI: 10.1089/ars.2012.5136] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
SIGNIFICANCE During the Legume-Rhizobium symbiosis, hydrogen peroxide (H(2)O(2)) and nitric oxide (NO) appear to play an important signaling role in the establishment and the functioning of this interaction. Modifications of the levels of these reactive species in both partners impair either the development of the nodules (new root organs formed on the interaction) or their N(2)-fixing activity. RECENT ADVANCES NADPH oxidases (Noxs) have been recently described as major sources of H(2)O(2) production, via superoxide anion dismutation, during symbiosis. Nitrate reductases (NR) and electron transfer chains from both partners were found to significantly contribute to NO production in N(2)-fixing nodules. Both S-sulfenylated and S-nitrosylated proteins have been detected during early interaction and in functioning nodules, linking reactive oxygen species (ROS)/NO production to redox-based protein regulation. NO was also found to play a metabolic role in nodule energy metabolism. CRITICAL ISSUES H(2)O(2) may control the infection process and the subsequent bacterial differentiation into the symbiotic form. NO is required for an optimal establishment of symbiosis and appears to be a key player in nodule senescence. FUTURE DIRECTIONS A challenging question is to define more precisely when and where reactive species are generated and to develop adapted tools to detect their production in vivo. To investigate the role of Noxs and NRs in the production of H(2)O(2) and NO, respectively, the use of mutants under the control of organ-specific promoters will be of crucial interest. The balance between ROS and NO production appears to be a key point to understand the redox regulation of symbiosis.
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Affiliation(s)
- Alain Puppo
- Institut Sophia Agrobiotech, TGU INRA 1355-CNRS 7254, Université de Nice-Sophia Antipolis, Sophia-Antipolis, France.
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Sullivan JT, Brown SD, Ronson CW. The NifA-RpoN regulon of Mesorhizobium loti strain R7A and its symbiotic activation by a novel LacI/GalR-family regulator. PLoS One 2013; 8:e53762. [PMID: 23308282 PMCID: PMC3538637 DOI: 10.1371/journal.pone.0053762] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/04/2012] [Indexed: 11/19/2022] Open
Abstract
Mesorhizobium loti is the microsymbiont of Lotus species, including the model legume L. japonicus. M. loti differs from other rhizobia in that it contains two copies of the key nitrogen fixation regulatory gene nifA, nifA1 and nifA2, both of which are located on the symbiosis island ICEMlSym(R7A). M. loti R7A also contains two rpoN genes, rpoN1 located on the chromosome outside of ICEMlSym(R7A) and rpoN2 that is located on ICEMlSym(R7A). The aims of the current work were to establish how nifA expression was activated in M. loti and to characterise the NifA-RpoN regulon. The nifA2 and rpoN2 genes were essential for nitrogen fixation whereas nifA1 and rpoN1 were dispensable. Expression of nifA2 was activated, possibly in response to an inositol derivative, by a novel regulator of the LacI/GalR family encoded by the fixV gene located upstream of nifA2. Other than the well-characterized nif/fix genes, most NifA2-regulated genes were not required for nitrogen fixation although they were strongly expressed in nodules. The NifA-regulated nifZ and fixU genes, along with nifQ which was not NifA-regulated, were required in M. loti for a fully effective symbiosis although they are not present in some other rhizobia. The NifA-regulated gene msi158 that encodes a porin was also required for a fully effective symbiosis. Several metabolic genes that lacked NifA-regulated promoters were strongly expressed in nodules in a NifA2-dependent manner but again mutants did not have an overt symbiotic phenotype. In summary, many genes encoded on ICEMlSym(R7A) were strongly expressed in nodules but not free-living rhizobia, but were not essential for symbiotic nitrogen fixation. It seems likely that some of these genes have functional homologues elsewhere in the genome and that bacteroid metabolism may be sufficiently plastic to adapt to loss of certain enzymatic functions.
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Affiliation(s)
- John T. Sullivan
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Steven D. Brown
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Clive W. Ronson
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- * E-mail:
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Ormeño-Orrillo E, Menna P, Almeida LGP, Ollero FJ, Nicolás MF, Pains Rodrigues E, Shigueyoshi Nakatani A, Silva Batista JS, Oliveira Chueire LM, Souza RC, Ribeiro Vasconcelos AT, Megías M, Hungria M, Martínez-Romero E. Genomic basis of broad host range and environmental adaptability of Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 which are used in inoculants for common bean (Phaseolus vulgaris L.). BMC Genomics 2012; 13:735. [PMID: 23270491 PMCID: PMC3557214 DOI: 10.1186/1471-2164-13-735] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 12/15/2012] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Rhizobium tropici CIAT 899 and Rhizobium sp. PRF 81 are α-Proteobacteria that establish nitrogen-fixing symbioses with a range of legume hosts. These strains are broadly used in commercial inoculants for application to common bean (Phaseolus vulgaris) in South America and Africa. Both strains display intrinsic resistance to several abiotic stressful conditions such as low soil pH and high temperatures, which are common in tropical environments, and to several antimicrobials, including pesticides. The genetic determinants of these interesting characteristics remain largely unknown. RESULTS Genome sequencing revealed that CIAT 899 and PRF 81 share a highly-conserved symbiotic plasmid (pSym) that is present also in Rhizobium leucaenae CFN 299, a rhizobium displaying a similar host range. This pSym seems to have arisen by a co-integration event between two replicons. Remarkably, three distinct nodA genes were found in the pSym, a characteristic that may contribute to the broad host range of these rhizobia. Genes for biosynthesis and modulation of plant-hormone levels were also identified in the pSym. Analysis of genes involved in stress response showed that CIAT 899 and PRF 81 are well equipped to cope with low pH, high temperatures and also with oxidative and osmotic stresses. Interestingly, the genomes of CIAT 899 and PRF 81 had large numbers of genes encoding drug-efflux systems, which may explain their high resistance to antimicrobials. Genome analysis also revealed a wide array of traits that may allow these strains to be successful rhizosphere colonizers, including surface polysaccharides, uptake transporters and catabolic enzymes for nutrients, diverse iron-acquisition systems, cell wall-degrading enzymes, type I and IV pili, and novel T1SS and T5SS secreted adhesins. CONCLUSIONS Availability of the complete genome sequences of CIAT 899 and PRF 81 may be exploited in further efforts to understand the interaction of tropical rhizobia with common bean and other legume hosts.
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Affiliation(s)
- Ernesto Ormeño-Orrillo
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Pâmela Menna
- Embrapa Soja, C. P. 231, Londrina, Paraná, 86001-970, Brazil
| | - Luiz Gonzaga P Almeida
- Laboratório Nacional de Computação Científica (LNCC), Avenida Getúlio Vargas 333, Petrópolis, Rio de Janeiro, Brazil
| | | | - Marisa Fabiana Nicolás
- Laboratório Nacional de Computação Científica (LNCC), Avenida Getúlio Vargas 333, Petrópolis, Rio de Janeiro, Brazil
| | | | | | | | | | - Rangel Celso Souza
- Laboratório Nacional de Computação Científica (LNCC), Avenida Getúlio Vargas 333, Petrópolis, Rio de Janeiro, Brazil
| | | | - Manuel Megías
- Universidad de Sevilla, Apdo Postal 874, Sevilla, 41080, Spain
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Vercruysse M, Fauvart M, Beullens S, Braeken K, Cloots L, Engelen K, Marchal K, Michiels J. A comparative transcriptome analysis of Rhizobium etli bacteroids: specific gene expression during symbiotic nongrowth. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2011; 24:1553-1561. [PMID: 21809980 DOI: 10.1094/mpmi-05-11-0140] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Rhizobium etli occurs either in a nitrogen-fixing symbiosis with its host plant, Phaseolus vulgaris, or free-living in the soil. During both conditions, the bacterium has been suggested to reside primarily in a nongrowing state. Using genome-wide transcriptome profiles, we here examine the molecular basis of the physiological adaptations of rhizobia to nongrowth inside and outside of the host. Compared with exponentially growing cells, we found an extensive overlap of downregulated growth-associated genes during both symbiosis and stationary phase, confirming the essentially nongrowing state of nitrogen-fixing bacteroids in determinate nodules that are not terminally differentiated. In contrast, the overlap of upregulated genes was limited. Generally, actively growing cells have hitherto been used as reference to analyze symbiosis-specific expression. However, this prevents the distinction between differential expression arising specifically from adaptation to a symbiotic lifestyle and features associated with nongrowth in general. Using stationary phase as the reference condition, we report a distinct transcriptome profile for bacteroids, containing 203 induced and 354 repressed genes. Certain previously described symbiosis-specific characteristics, such as the downregulation of amino acid metabolism genes, were no longer observed, indicating that these features are more likely due to the nongrowing state of bacteroids rather than representing bacteroid-specific physiological adaptations.
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Saeki K. Rhizobial measures to evade host defense strategies and endogenous threats to persistent symbiotic nitrogen fixation: a focus on two legume-rhizobium model systems. Cell Mol Life Sci 2011; 68:1327-39. [PMID: 21365276 PMCID: PMC11114668 DOI: 10.1007/s00018-011-0650-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2011] [Revised: 02/15/2011] [Accepted: 02/15/2011] [Indexed: 10/18/2022]
Abstract
The establishment and maintenance of rhizobium-legume symbioses require a sequence of highly regulated and coordinated events between the organisms. Although the interaction is mutually beneficial under nitrogen-limited conditions, it can resemble a pathogenic infection at some stages. Some host legumes mount defense reactions, including the production of reactive oxygen species (ROS) and defensin-like antimicrobial compounds. To subvert these host defenses, the infecting rhizobial cells can use measures to passively protect themselves and actively modulate host functions. This review first describes the establishment and maintenance of active nodules, as well as the external and endogenous attack and threat stages. Next, recent studies of ROS scavenging enzymes, the BacA protein originally found in Sinorhizobium meliloti, and the type III/IV secretion systems are discussed, with a focus on two legume-rhizobium model systems.
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Affiliation(s)
- Kazuhiko Saeki
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Kitauoya Nishimachi, Nara, Japan.
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27
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Vercruysse M, Fauvart M, Jans A, Beullens S, Braeken K, Cloots L, Engelen K, Marchal K, Michiels J. Stress response regulators identified through genome-wide transcriptome analysis of the (p)ppGpp-dependent response in Rhizobium etli. Genome Biol 2011; 12:R17. [PMID: 21324192 PMCID: PMC3188799 DOI: 10.1186/gb-2011-12-2-r17] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 02/01/2011] [Accepted: 02/16/2011] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The alarmone (p)ppGpp mediates a global reprogramming of gene expression upon nutrient limitation and other stresses to cope with these unfavorable conditions. Synthesis of (p)ppGpp is, in most bacteria, controlled by RelA/SpoT (Rsh) proteins. The role of (p)ppGpp has been characterized primarily in Escherichia coli and several Gram-positive bacteria. Here, we report the first in-depth analysis of the (p)ppGpp-regulon in an α-proteobacterium using a high-resolution tiling array to better understand the pleiotropic stress phenotype of a relA/rsh mutant. RESULTS We compared gene expression of the Rhizobium etli wild type and rsh (previously rel) mutant during exponential and stationary phase, identifying numerous (p)ppGpp targets, including small non-coding RNAs. The majority of the 834 (p)ppGpp-dependent genes were detected during stationary phase. Unexpectedly, 223 genes were expressed (p)ppGpp-dependently during early exponential phase, indicating the hitherto unrecognized importance of (p)ppGpp during active growth. Furthermore, we identified two (p)ppGpp-dependent key regulators for survival during heat and oxidative stress and one regulator putatively involved in metabolic adaptation, namely extracytoplasmic function sigma factor EcfG2/PF00052, transcription factor CH00371, and serine protein kinase PrkA. CONCLUSIONS The regulatory role of (p)ppGpp in R. etli stress adaptation is far-reaching in redirecting gene expression during all growth phases. Genome-wide transcriptome analysis of a strain deficient in a global regulator, and exhibiting a pleiotropic phenotype, enables the identification of more specific regulators that control genes associated with a subset of stress phenotypes. This work is an important step toward a full understanding of the regulatory network underlying stress responses in α-proteobacteria.
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Affiliation(s)
- Maarten Vercruysse
- Centre of Microbial and Plant Genetics, Katholiek Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
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Alquéres SMC, Oliveira JHM, Nogueira EM, Guedes HV, Oliveira PL, Câmara F, Baldani JI, Martins OB. Antioxidant pathways are up-regulated during biological nitrogen fixation to prevent ROS-induced nitrogenase inhibition in Gluconacetobacter diazotrophicus. Arch Microbiol 2010; 192:835-41. [PMID: 20697694 PMCID: PMC2939349 DOI: 10.1007/s00203-010-0609-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 06/17/2010] [Accepted: 07/19/2010] [Indexed: 01/24/2023]
Abstract
Gluconacetobacter diazotrophicus, an endophyte isolated from sugarcane, is a strict aerobe that fixates N2. This process is catalyzed by nitrogenase and requires copious amounts of ATP. Nitrogenase activity is extremely sensitive to inhibition by oxygen and reactive oxygen species (ROS). However, the elevated oxidative metabolic rates required to sustain biological nitrogen fixation (BNF) may favor an increased production of ROS. Here, we explored this paradox and observed that ROS levels are, in fact, decreased in nitrogen-fixing cells due to the up-regulation of transcript levels of six ROS-detoxifying genes. A cluster analyses based on common expression patterns revealed the existence of a stable cluster with 99.8% similarity made up of the genes encoding the α-subunit of nitrogenase Mo–Fe protein (nifD), superoxide dismutase (sodA) and catalase type E (katE). Finally, nitrogenase activity was inhibited in a dose-dependent manner by paraquat, a redox cycler that increases cellular ROS levels. Our data revealed that ROS can strongly inhibit nitrogenase activity, and G. diazotrophicus alters its redox metabolism during BNF by increasing antioxidant transcript levels resulting in a lower ROS generation. We suggest that careful controlled ROS production during this critical phase is an adaptive mechanism to allow nitrogen fixation.
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Affiliation(s)
- Sylvia M C Alquéres
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, RJ, Brazil.
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Characterization of the NifA-RpoN regulon in Rhizobium etli in free life and in symbiosis with Phaseolus vulgaris. Appl Environ Microbiol 2010; 76:4510-20. [PMID: 20453139 DOI: 10.1128/aem.02007-09] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The NifA-RpoN complex is a master regulator of the nitrogen fixation genes in alphaproteobacteria. Based on the complete Rhizobium etli genome sequence, we constructed an R. etli CFN42 oligonucleotide (70-mer) microarray and utilized this tool, reverse transcription (RT)-PCR analysis (transcriptomics), proteomics, and bioinformatics to decipher the NifA-RpoN regulon under microaerobic conditions (free life) and in symbiosis with bean plants. The R. etli NifA-RpoN regulon was determined to contain 78 genes, including the genes involved in nitrogen fixation, and the analyses revealed 42 new NifA-RpoN-dependent genes. More importantly, this study demonstrated that the NifA-RpoN regulon is composed of genes and proteins that have very diverse functions, that play fundamental and previously less appreciated roles in regulating the normal physiology of the cell, and that have important functions in providing adequate conditions for efficient nitrogen fixation in symbiosis. The R. etli NifA-RpoN regulon defined here has some components in common with other NifA-RpoN regulons described previously, but the vast majority of the components have been found only in the R. etli regulon, suggesting that they have a specific role in this bacterium and particular requirements during nitrogen fixation compared with other symbiotic bacterial models.
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Proteomic alterations explain phenotypic changes in Sinorhizobium meliloti lacking the RNA chaperone Hfq. J Bacteriol 2010; 192:1719-29. [PMID: 20081032 DOI: 10.1128/jb.01429-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The ubiquitous bacterial RNA-binding protein Hfq is involved in stress resistance and pathogenicity. In Sinorhizobium meliloti, Hfq is essential for the establishment of symbiosis with Medicago sativa and for nitrogen fixation. A proteomic analysis identifies 55 proteins with significantly affected expression in the hfq mutant; most of them are involved in cell metabolism or stress resistance. Important determinants of oxidative stress resistance, such as CysK, Gsh, Bfr, SodC, KatB, KatC, and a putative peroxiredoxine (SMc00072), are downregulated in the hfq mutant. The hfq mutant is affected for H(2)O(2), menadione, and heat stress resistance. Part of these defects could result from the reductions of rpoE1, rpoE2, rpoE3, and rpoE4 expression levels in the hfq mutant. Some proteins required for efficient symbiosis are reduced in the hfq mutant, contributing to the drastic defect in nodulation observed in this mutant.
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31
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Comparative cytochemical analysis of hydrogen peroxide distribution in pea ineffective mutant SGEFix--1 (sym40) and initial line SGE. ACTA ACUST UNITED AC 2009. [DOI: 10.17816/ecogen733-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Comparative cytochemical analysis has revealed differences in hydrogen peroxide distribution in symbiotic nodules of pea initial line SGE and mutant SGEFix<sup>-</sup>-1 (sym40). In the initial line SGE, precipitates of cerium perhydroxide were deposited in the walls of infection threads and in adjacent material in the luminal matrix. In mutant SGEFix<sup>-</sup>-1, an increased deposition of cerium perhydroxide precipitates was observed in the matrix of hypertrophied infection droplets, round bacteria contained in infection threads and also around juvenile bacteroids. The observed pattern of hydrogen peroxide distribution indicates that bacteria in infected cells of mutant nodules are exposed to a stronger oxidative stress compared with nodules of the initial line.
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Fauvart M, Verstraeten N, Dombrecht B, Venmans R, Beullens S, Heusdens C, Michiels J. Rhizobium etli HrpW is a pectin-degrading enzyme and differs from phytopathogenic homologues in enzymically crucial tryptophan and glycine residues. Microbiology (Reading) 2009; 155:3045-3054. [DOI: 10.1099/mic.0.027599-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
While establishing a nitrogen-fixing symbiosis with leguminous plants, rhizobia are faced with the problem of penetrating the plant cell wall at several stages of the infection process. One of the major components of this barrier is pectin, a heteropolysaccharide composed mainly of galacturonic acid subunits. So far, no enzymes capable of degrading pectin have been isolated from rhizobia. Here, we make an inventory of rhizobial candidate pectinolytic enzymes based on available genome sequence data and present an initial biochemical and functional characterization of a protein selected from this list. Rhizobium etli hrpW is associated with genes encoding a type III secretion system, a macromolecular structure that allows bacteria to directly inject so-called effector proteins into a eukaryotic host's cell cytosol and an essential virulence determinant of many Gram-negative pathogenic bacteria. In contrast to harpin HrpW from phytopathogens, R. etli HrpW possesses pectate lyase activity and is most active on highly methylated substrates. Through comparative sequence analysis, three amino acid residues crucial for the observed enzymic activity were identified: Trp192, Gly212 and Gly213. Their importance was confirmed by site-directed mutagenesis and biochemical characterization of the resulting proteins, with the tryptophan mutant showing no detectable pectate lyase activity and the double-glycine mutant's activity reduced by about 80 %. Surprisingly, despite hrpW expression being induced specifically on the plant root surface, a knockout mutation of the gene does not appear to affect symbiosis with the common bean Phaseolus vulgaris.
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Affiliation(s)
- Maarten Fauvart
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Natalie Verstraeten
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Bruno Dombrecht
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Ruth Venmans
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Serge Beullens
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Christophe Heusdens
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium
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Chang C, Damiani I, Puppo A, Frendo P. Redox changes during the legume-rhizobium symbiosis. MOLECULAR PLANT 2009; 2:370-377. [PMID: 19825622 DOI: 10.1093/mp/ssn090] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Reactive Oxygen Species (ROS) are continuously produced as a result of aerobic metabolism or in response to biotic and abiotic stresses. ROS are not only toxic by-products of aerobic metabolism, but are also signaling molecules involved in plant growth and environmental adaptation. Antioxidants can protect the cell from oxidative damage by scavenging the ROS. Thus, they play an important role in optimizing cell function by regulating cellular redox state and modifying gene expression. This article aims to review recent studies highlighting the role of redox signals in establishing and maintaining symbiosis between rhizobia and legumes.
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Affiliation(s)
- Christine Chang
- UMR INRA-Université de Nice-Sophia Antipolis-CNRS Interactions Biotiques et Santé Végétale, 400 Route des Chappes, BP167, 06903 Sophia Antipolis Cedex, France
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34
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Martínez-Salazar JM, Sandoval-Calderón M, Guo X, Castillo-Ramírez S, Reyes A, Loza MG, Rivera J, Alvarado-Affantranger X, Sánchez F, González V, Dávila G, Ramírez-Romero MA. The Rhizobium etli RpoH1 and RpoH2 sigma factors are involved in different stress responses. MICROBIOLOGY-SGM 2009; 155:386-397. [PMID: 19202087 DOI: 10.1099/mic.0.021428-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The physiological role and transcriptional expression of Rhizobium etli sigma factors rpoH1 and rpoH2 are reported in this work. Both rpoH1 and rpoH2 were able to complement the temperature-sensitive phenotype of an Escherichia coli rpoH mutant. The R. etli rpoH1 mutant was sensitive to heat shock, sodium hypochlorite and hydrogen peroxide, whereas the rpoH2 mutant was sensitive to NaCl and sucrose. The rpoH2 rpoH1 double mutant had increased sensitivity to heat shock and oxidative stress when compared with the rpoH1 single mutant. This suggests that in R. etli, RpoH1 is the main heat-shock sigma factor, but a more complete protective response could be achieved with the participation of RpoH2. Conversely, RpoH2 is involved in osmotic tolerance. In symbiosis with bean plants, the R. etli rpoH1 and rpoH2 rpoH1 mutants still elicited nodule formation, but exhibited reduced nitrogenase activity and bacterial viability in early and late symbiosis compared with nodules produced by rpoH2 mutants and wild-type strains. In addition, nodules formed by R. etli rpoH1 and rpoH2 rpoH1 mutants showed premature senescence. It was also determined that fixNf and fixKf expression was affected in rpoH1 mutants. Both rpoH genes were induced under microaerobic conditions and in the stationary growth phase, but not in response to heat shock. Analysis of the upstream region of rpoH1 revealed a sigma70 and a probable sigmaE promoter, whereas in rpoH2, one probable sigmaE-dependent promoter was detected. In conclusion, the two RpoH proteins operate under different stress conditions, RpoH1 in heat-shock and oxidative responses, and RpoH2 in osmotic tolerance.
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Affiliation(s)
- Jaime M Martínez-Salazar
- Programa de Ingeniería Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Mario Sandoval-Calderón
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Xianwu Guo
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Santiago Castillo-Ramírez
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Alma Reyes
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Maria G Loza
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Javier Rivera
- Programa de Ingeniería Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Xochitl Alvarado-Affantranger
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, CP 62271 Cuernavaca, Morelos, México
| | - Federico Sánchez
- Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, CP 62271 Cuernavaca, Morelos, México
| | - Víctor González
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Guillermo Dávila
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
| | - Miguel A Ramírez-Romero
- Programa de Genómica Evolutiva, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, CP 62210 Cuernavaca, Morelos, México
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Hanyu M, Fujimoto H, Tejima K, Saeki K. Functional differences of two distinct catalases in Mesorhizobium loti MAFF303099 under free-living and symbiotic conditions. J Bacteriol 2009; 191:1463-71. [PMID: 19074374 PMCID: PMC2648221 DOI: 10.1128/jb.01583-08] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2008] [Accepted: 12/04/2008] [Indexed: 11/20/2022] Open
Abstract
Protection against reactive oxygen species (ROS) is important for legume-nodulating rhizobia during the establishment and maintenance of symbiosis, as well as under free-living conditions, because legume hosts might assail incoming microbes with ROS and because nitrogenase is extremely sensitive to ROS. We generated mutants of two potential catalase genes in Mesorhizobium loti MAFF303099 to investigate their physiological significance. Biochemical results indicated that genes with the locus tags mlr2101 and mlr6940 encoded a monofunctional catalase and a bifunctional catalase-peroxidase, respectively, that were named katE and katG. Under free-living conditions, the katG mutant demonstrated an extended generation time and elevated sensitivity to exogenous H(2)O(2), whereas the katE mutant exhibited no generation time extension and only a slight increase in sensitivity to exogenous H(2)O(2). However, the katE mutant showed a marked decrease in its survival rate during the stationary phase. With regard to symbiotic capacities with Lotus japonicus, the katG mutant was indistinguishable from the wild type; nevertheless, the mutants with disrupted katE formed nodules with decreased nitrogen fixation capacities (about 50 to 60%) compared to those formed by the wild type. These mutant phenotypes agreed with the expression profiles showing that transcription of katG, but not katE, was high during the exponential growth phase and that transcription levels of katE versus sigA were elevated during stationary phase and were approximately fourfold higher in bacteroids than mid-exponential-phase cells. Our results revealed functional separation of the two catalases, as well as the importance of KatE under conditions of strong growth limitation.
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Affiliation(s)
- Masaki Hanyu
- Department of Biological Sciences, Nara Women's University, Japan
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Mandon K, Pauly N, Boscari A, Brouquisse R, Frendo P, Demple B, Puppo A. ROS in the Legume-Rhizobium Symbiosis. REACTIVE OXYGEN SPECIES IN PLANT SIGNALING 2009. [DOI: 10.1007/978-3-642-00390-5_8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Braeken K, Fauvart M, Vercruysse M, Beullens S, Lambrichts I, Michiels J. Pleiotropic effects of a rel mutation on stress survival of Rhizobium etli CNPAF512. BMC Microbiol 2008; 8:219. [PMID: 19077212 PMCID: PMC2631030 DOI: 10.1186/1471-2180-8-219] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Accepted: 12/10/2008] [Indexed: 12/04/2022] Open
Abstract
Background The rel gene of Rhizobium etli (relRet), the nodulating endosymbiont of the common bean plant, determines the cellular level of the alarmone (p)ppGpp and was previously shown to affect free-living growth and symbiosis. Here, we demonstrate its role in cellular adaptation and survival in response to various stresses. Results Growth of the R. etli relRet mutant was strongly reduced or abolished in the presence of elevated NaCl levels or at 37°C, compared to the wild type. In addition, depending on the cell density, decreased survival of exponentially growing or stationary phase relRet mutant cells was obtained after H2O2, heat or NaCl shock compared to the wild-type strain. Survival of unstressed stationary phase cultures was differentially affected depending on the growth medium used. Colony forming units (CFU) of relRet mutant cultures continuously decreased in minimal medium supplemented with succinate, whereas wild-type cultures stabilised at higher CFU levels. Microscopic examination of stationary phase cells indicated that the relRet mutant was unable to reach the typical coccoid morphology of the wild type in stationary phase cultures. Assessment of stress resistance of re-isolated bacteroids showed increased sensitivity of the relRet mutant to H2O2 and a slightly increased resistance to elevated temperature (45°C) or NaCl shock, compared to wild-type bacteroids. Conclusion The relRet gene is an important factor in regulating rhizobial physiology, during free-living growth as well as in symbiotic conditions. Additionally, differential responses to several stresses applied to bacteroids and free-living exponential or stationary phase cells point to essential physiological differences between the different states.
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Affiliation(s)
- Kristien Braeken
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium.
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García-de Los Santos A, López E, Cubillas CA, Noel KD, Brom S, Romero D. Requirement of a plasmid-encoded catalase for survival of Rhizobium etli CFN42 in a polyphenol-rich environment. Appl Environ Microbiol 2008; 74:2398-403. [PMID: 18310436 PMCID: PMC2293148 DOI: 10.1128/aem.02457-07] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 02/15/2008] [Indexed: 11/20/2022] Open
Abstract
Nitrogen-fixing bacteria collectively called rhizobia are adapted to live in polyphenol-rich environments. The mechanisms that allow these bacteria to overcome toxic concentrations of plant polyphenols have not been clearly elucidated. We used a crude extract of polyphenols released from the seed coat of the black bean to simulate a polyphenol-rich environment and analyze the response of the bean-nodulating strain Rhizobium etli CFN42. Our results showed that the viability of the wild type as well as that of derivative strains cured of plasmids p42a, p42b, p42c, and p42d or lacking 200 kb of plasmid p42e was not affected in this environment. In contrast, survival of the mutant lacking plasmid p42f was severely diminished. Complementation analysis revealed that the katG gene located on this plasmid, encoding the only catalase present in this bacterium, restored full resistance to testa polyphenols. Our results indicate that oxidation of polyphenols due to interaction with bacterial cells results in the production of a high quantity of H(2)O(2), whose removal by the katG-encoded catalase plays a key role for cell survival in a polyphenol-rich environment.
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Braeken K, Daniels R, Vos K, Fauvart M, Bachaspatimayum D, Vanderleyden J, Michiels J. Genetic determinants of swarming in Rhizobium etli. MICROBIAL ECOLOGY 2008; 55:54-64. [PMID: 17394038 DOI: 10.1007/s00248-007-9250-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 03/02/2007] [Accepted: 03/05/2007] [Indexed: 05/14/2023]
Abstract
Swarming motility is considered to be a social phenomenon that enables groups of bacteria to move coordinately atop solid surfaces. The differentiated swarmer cell population is embedded in an extracellular slime layer, and the phenomenon has previously been linked with biofilm formation and virulence. The gram-negative nitrogen-fixing soil bacterium Rhizobium etli CNPAF512 was previously shown to display swarming behavior on soft agar plates. In a search for novel genetic determinants of swarming, a detailed analysis of the swarming behavior of 700 miniTn5 mutants of R. etli was performed. Twenty-four mutants defective in swarming or displaying abnormal swarming patterns were identified and could be divided into three groups based on their swarming pattern. Fourteen mutants were completely swarming deficient, five mutants showed an atypical swarming pattern with no completely smooth edge and local extrusions, and five mutants displayed an intermediate swarming phenotype. Sequence analysis of the targeted genes indicated that the mutants were likely affected in quorum-sensing, polysaccharide composition or export, motility, and amino acid and polyamines metabolism. Several of the identified mutants displayed a reduced symbiotic nitrogen fixation activity.
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Affiliation(s)
- Kristien Braeken
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001, Heverlee, Belgium
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Muglia CI, Grasso DH, Aguilar OM. Rhizobium tropici response to acidity involves activation of glutathione synthesis. MICROBIOLOGY-SGM 2007; 153:1286-1296. [PMID: 17379738 DOI: 10.1099/mic.0.2006/003483-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Rhizobium tropici CIAT899 displays intrinsic tolerance to acidity, and efficiently nodulates Phaseolus vulgaris at low pH. By characterizing a gshB mutant strain, glutathione has been previously demonstrated to be essential for R. tropici tolerance to acid stress. The wild-type gshB gene region has been cloned and its transcription profile has been characterized by using quantitative real-time PCR and transcriptional gene fusions. Activation of the gshB gene under acid-stress conditions was demonstrated. gshB is also induced by UV irradiation. Upstream from gshB a putative sigma(70) promoter element and an inverted repeat sequence were identified, which are proposed to be involved in expression under neutral and acidic conditions, respectively. Gel retardation assays indicate that transcription in acid conditions may involve protein binding to an upstream regulatory region.
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Affiliation(s)
- Cecilia I Muglia
- Instituto de Bioquímica y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900, La Plata, Argentina
| | - Daniel H Grasso
- Instituto de Bioquímica y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900, La Plata, Argentina
| | - O Mario Aguilar
- Instituto de Bioquímica y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900, La Plata, Argentina
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Fauvart M, Braeken K, Daniels R, Vos K, Ndayizeye M, Noben JP, Robben J, Vanderleyden J, Michiels J. Identification of a novel glyoxylate reductase supports phylogeny-based enzymatic substrate specificity prediction. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:1092-8. [PMID: 17693143 DOI: 10.1016/j.bbapap.2007.06.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Revised: 06/12/2007] [Accepted: 06/25/2007] [Indexed: 11/26/2022]
Abstract
Phylogenetic analysis of the superfamily of D-2-hydroxyacid dehydrogenases identified the previously unrecognized cluster of glyoxylate/hydroxypyruvate reductases (GHPR). Based on the genome sequence of Rhizobium etli, the nodulating endosymbiont of the common bean plant, we predicted a putative 3-phosphoglycerate dehydrogenase to exhibit GHPR activity instead. The protein was overexpressed and purified. The enzyme is homodimeric under native conditions and is indeed capable of reducing both glyoxylate and hydroxypyruvate. Other substrates are phenylpyruvate and ketobutyrate. The highest activity was observed with glyoxylate and phenylpyruvate, both having approximately the same kcat/Km ratio. This kind of substrate specificity has not been reported previously for a GHPR. The optimal pH for the reduction of phenylpyruvate to phenyllactate is pH 7. These data lend support to the idea of predicting enzymatic substrate specificity based on phylogenetic clustering.
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Affiliation(s)
- Maarten Fauvart
- Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium
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Piñero S, Rivera J, Romero D, Cevallos MA, Martínez A, Bolívar F, Gosset G. Tyrosinase from Rhizobium etli Is Involved in Nodulation Efficiency and Symbiosis-Associated Stress Resistance. J Mol Microbiol Biotechnol 2007; 13:35-44. [PMID: 17693711 DOI: 10.1159/000103595] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Tyrosinase (EC 1.14.18.1) is a monophenol oxidase responsible for the synthesis of the black pigment known as melanin. The tyrosinase gene (melA) is plasmid-encoded in many rhizobial species. In Rhizobium etli CFN42, the genetic location of melA in the symbiotic plasmid (p42d) and its RpoN-NifA regulation suggest an involvement in symbiosis. In this work, we analyzed the symbiotic phenotype of a streptomycin-resistant derivative of CFN42 (CE3), a melA mutant (SP2) and a complemented strain (SP66), demonstrating that melA inactivation reduced nodule formation rate and diminished total nodule number by 27% when compared to the CE3 strain. The nitrogen fixation capacity of the mutant strain was not affected. Also, in vitro assays were performed where the resistance of CE3, SP2 and SP66 strains to H(2)O(2) was evaluated; the melA mutant strain was consistently less resistant to peroxide. In another series of experiments, Escherichia coli W3110 strain expressing R. etli melA displayed enhanced resistance to p-hydroxybenzoic, vanillinic and syringic acids, which are phenolic compounds frequently found in the soil. Our results are the first to demonstrate a specific role for tyrosinase in R. etli: this enzyme is required during early symbiosis, apparently providing resistance against reactive oxygen species and phenolic compounds generated as part of the plant protective responses.
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Affiliation(s)
- Silvia Piñero
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología/UNAM, Cuernavaca, Mexico
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Cytryn EJ, Sangurdekar DP, Streeter JG, Franck WL, Chang WS, Stacey G, Emerich DW, Joshi T, Xu D, Sadowsky MJ. Transcriptional and physiological responses of Bradyrhizobium japonicum to desiccation-induced stress. J Bacteriol 2007; 189:6751-62. [PMID: 17660288 PMCID: PMC2045231 DOI: 10.1128/jb.00533-07] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The growth and persistence of rhizobia and bradyrhizobia in soils are negatively impacted by drought conditions. In this study, we used genome-wide transcriptional analyses to obtain a comprehensive understanding of the response of Bradyrhizobium japonicum to drought. Desiccation of cells resulted in the differential expression of 15 to 20% of the 8,453 [corrected] B. japonicum open reading frames, with considerable differentiation between early (after 4 h) and late (after 24 and 72 h) expressed genes. While 225 genes were universally up-regulated at all three incubation times in response to desiccation, an additional 43 and 403 up-regulated genes were common to the 4/24- and 24/72-h incubation times, respectively. Desiccating conditions resulted in the significant induction (>2.0-fold) of the trehalose-6-phosphate synthetase (otsA), trehalose-6-phosphate phosphatase (otsB), and trehalose synthase (treS) genes, which encode two of the three trehalose synthesis pathways found in B. japonicum. Gene induction was correlated with an elevated intracellular concentration of trehalose and increased activity of trehalose-6-phosphate synthetase, collectively supporting the hypothesis that this disaccharide plays a prominent and important role in promoting desiccation tolerance in B. japonicum. Microarray data also indicated that sigma(54)- and sigma(24)-associated transcriptional regulators and genes encoding isocitrate lyase, oxidative stress responses, the synthesis and transport of exopolysaccharides, heat shock response proteins, enzymes for the modification and repair of nucleic acids, and the synthesis of pili and flagella are also involved in the response of B. japonicum to desiccation. Polyethylene glycol-generated osmotic stress induced significantly fewer genes than those transcriptionally activated by desiccation. However, 67 genes were commonly induced under both conditions. Taken together, these results suggest that B. japonicum directly responds to desiccation by adapting to changes imparted by reduced water activity, such as the synthesis of trehalose and polysaccharides and, secondarily, by the induction of a wide variety of proteins involved in protection of the cell membrane, repair of DNA damage, stability and integrity of proteins, and oxidative stress responses.
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Affiliation(s)
- Eddie J Cytryn
- Department of Soil, Water, and Climate, BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA [corrected]
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Benhassine T, Fauvart M, Vanderleyden J, Michiels J. Interaction of an IHF-like protein with the Rhizobium etli nifA promoter. FEMS Microbiol Lett 2007; 271:20-6. [PMID: 17403047 DOI: 10.1111/j.1574-6968.2007.00699.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The nifA gene fulfills an essential role in the regulation of nitrogen fixation genes in Rhizobium etli. Transcription analysis of the nifA gene, assessed using promoter deletions, indicated an oxygen-independent expression, threefold higher during symbiosis as compared with free-living conditions. Electrophoretic mobility shift assays using those nifA promoter deletion fragments, which were actively transcribed, demonstrated the specific interaction with R. etli cellular protein(s) resulting in the formation of two DNA-protein complexes. An interacting protein was purified by liquid chromatography on Heparin Sepharose and Mono S columns. The purified 12 kDa R. etli protein cross-reacted with antibodies directed against Escherichia coli integration host factor (IHF). Furthermore, purified E. coli IHF was able to specifically bind to the R. etli nifA promoter region. These results point to an as yet undisclosed function of IHF in the regulation of R. etli nifA expression.
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Affiliation(s)
- Traki Benhassine
- Laboratoire de Biologie Cellulaire et Moléculaire, Faculté des Sciences Biologiques, USTHB, Alger, Algérie
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Ekman M, Tollbäck P, Klint J, Bergman B. Protein expression profiles in an endosymbiotic cyanobacterium revealed by a proteomic approach. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:1251-61. [PMID: 17073307 DOI: 10.1094/mpmi-19-1251] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Molecular mechanisms behind adaptations in the cyanobacterium (Nostoc sp.) to a life in endosymbiosis with plants are still not clarified, nor are the interactions between the partners. To get further insights, the proteome of a Nostoc strain, freshly isolated from the symbiotic gland tissue of the angiosperm Gunnera manicata Linden, was analyzed and compared with the proteome of the same strain when free-living. Extracted proteins were separated by two-dimensional gel electrophoresis and were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry combined with tandem mass spectrometry. Even when the higher percentage of differentiated cells (heterocysts) in symbiosis was compensated for, the majority of the proteins detected in the symbiotic cyanobacteria were present in the free-living counterpart, indicating that most cellular processes were common for both stages. However, differential expression profiling revealed a significant number of proteins to be down-regulated or missing in the symbiotic stage, while others were more abundant or only expressed in symbiosis. The differential protein expression was primarily connected to i) cell envelope-associated processes, including proteins involved in exopolysaccharide synthesis and surface and membrane associated proteins, ii) to changes in growth and metabolic activities (C and N), including upregulation of nitrogenase and proteins involved in the oxidative pentose phosphate pathway and downregulation of Calvin cycle enzymes, and iii) to the dark, microaerobic conditions offered inside the Gunnera gland cells, including changes in relative phycobiliprotein concentrations. This is the first comprehensive analysis of proteins in the symbiotic state.
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Affiliation(s)
- Martin Ekman
- Department of Botany, Stockholm University, SE-106 91 Stockholm, Sweden.
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Chuchue T, Tanboon W, Prapagdee B, Dubbs JM, Vattanaviboon P, Mongkolsuk S. ohrR and ohr are the primary sensor/regulator and protective genes against organic hydroperoxide stress in Agrobacterium tumefaciens. J Bacteriol 2006; 188:842-51. [PMID: 16428387 PMCID: PMC1347339 DOI: 10.1128/jb.188.3.842-851.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genes involved in organic hydroperoxide protection in Agrobacterium tumefaciens were functionally evaluated. Gene inactivation studies and functional analyses have identified ohr, encoding a thiol peroxidase, as the gene primarily responsible for organic hydroperoxide protection in A. tumefaciens. An ohr mutant was sensitive to organic hydroperoxide killing and had a reduced capacity to metabolize organic hydroperoxides. ohr is located next to, and is divergently transcribed from, ohrR, encoding a sensor and transcription regulator of organic hydroperoxide stress. Transcription of both ohr and ohrR was induced by exposure to organic hydroperoxides but not by exposure to other oxidants. This induction required functional ohrR. The results of gel mobility shift and DNase I footprinting assays with purified OhrR, combined with in vivo promoter deletion analyses, confirmed that OhrR regulated both ohrR and ohr by binding to a single OhrR binding box that overlapped the ohrR and ohr promoters. ohrR and ohr are both required for the establishment of a novel cumene hydroperoxide-induced adaptive response. Inactivation or overexpression of other Prx family genes (prx1, prx2, prx3, bcp1, and bcp2) did not affect either the resistance to, or the ability to degrade, organic hydroperoxide. Taken together, the results of biochemical, gene regulation and physiological studies support the role of ohrR and ohr as the primary system in sensing and protecting A. tumefaciens from organic hydroperoxide stress.
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Affiliation(s)
- Tatsanee Chuchue
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Weerachai Tanboon
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Benjaphorn Prapagdee
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - James M. Dubbs
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Paiboon Vattanaviboon
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
- Corresponding author. Mailing address: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand. Phone: 662-574-0622, x1402. Fax: 662-574-2027. E-mail for S. Mongkolsuk: . E-mail for P. Vattanaviboon:
| | - Skorn Mongkolsuk
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand, Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
- Corresponding author. Mailing address: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand. Phone: 662-574-0622, x1402. Fax: 662-574-2027. E-mail for S. Mongkolsuk: . E-mail for P. Vattanaviboon:
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Yuan ZC, Zaheer R, Finan TM. Phosphate limitation induces catalase expression in Sinorhizobium meliloti, Pseudomonas aeruginosa and Agrobacterium tumefaciens. Mol Microbiol 2006; 58:877-94. [PMID: 16238634 DOI: 10.1111/j.1365-2958.2005.04874.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Growth of Sinorhizobium meliloti under Pi-limiting conditions induced expression of the major H2O2-inducible catalase (HPII) gene (katA) in this organism. This transcription required the PhoB transcriptional regulator and initiated from a promoter that was distinct from the OxyR-dependent promoter which activates katA transcription in response to addition of H2O2. In N2-fixing root nodules, katA was transcribed from the OxyR- and not the PhoB-dependent promoter. This is consistent with the accumulation of reactive oxygen species (ROS) in nodules and also indicates that bacteroids within nodules are not Pi-limited. Pi-limited growth also induced expression of catalase genes in Agrobacterium tumefaciens (HPI) and Pseudomonas aeruginosa (PA4236-HPI) suggesting that this may be a widespread phenomenon. The response is not a general stress response as in both S. meliloti and P. aeruginosa increased transcription is mediated by the phosphate responsive transcriptional activator PhoB. The phenotypic consequences of this response were demonstrated in S. meliloti by the dramatic increase in H2O2 resistance of wild type but not phoB mutant cells upon growth in Pi-limiting media. Our data indicate that in S. meliloti, katA and other genes whose products are involved in protection from oxidative stress are induced upon Pi-limitation. These observations suggest that as part of the response to Pi-limitation, S. meliloti, P. aeruginosa and A. tumefaciens have evolved a capacity to increase their resistance to oxidative stress. Whether this capacity evolved because Pi-starved cells generate more ROS or whether the physiological changes that occur in the cells in response to Pi-starvation render them more sensitive to ROS remains to be established.
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Affiliation(s)
- Ze-Chun Yuan
- Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1
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Rediers H, Rainey PB, Vanderleyden J, De Mot R. Unraveling the secret lives of bacteria: use of in vivo expression technology and differential fluorescence induction promoter traps as tools for exploring niche-specific gene expression. Microbiol Mol Biol Rev 2005; 69:217-61. [PMID: 15944455 PMCID: PMC1197422 DOI: 10.1128/mmbr.69.2.217-261.2005] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A major challenge for microbiologists is to elucidate the strategies deployed by microorganisms to adapt to and thrive in highly complex and dynamic environments. In vitro studies, including those monitoring genomewide changes, have proven their value, but they can, at best, mimic only a subset of the ensemble of abiotic and biotic stimuli that microorganisms experience in their natural habitats. The widely used gene-to-phenotype approach involves the identification of altered niche-related phenotypes on the basis of gene inactivation. However, many traits contributing to ecological performance that, upon inactivation, result in only subtle or difficult to score phenotypic changes are likely to be overlooked by this otherwise powerful approach. Based on the premise that many, if not most, of the corresponding genes will be induced or upregulated in the environment under study, ecologically significant genes can alternatively be traced using the promoter trap techniques differential fluorescence induction and in vivo expression technology (IVET). The potential and limitations are discussed for the different IVET selection strategies and system-specific variants thereof. Based on a compendium of genes that have emerged from these promoter-trapping studies, several functional groups have been distinguished, and their physiological relevance is illustrated with follow-up studies of selected genes. In addition to confirming results from largely complementary approaches such as signature-tagged mutagenesis, some unexpected parallels as well as distinguishing features of microbial phenotypic acclimation in diverse environmental niches have surfaced. On the other hand, by the identification of a large proportion of genes with unknown function, these promoter-trapping studies underscore how little we know about the secret lives of bacteria and other microorganisms.
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Affiliation(s)
- Hans Rediers
- Centre of Microbial and Plant Genetics, Heverlee, Belgium
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