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Wang X, Jiang Y, Liu H, Zhang X, Yuan H, Huang D, Wang T. In vitro assembly of the trehalose bi-enzyme complex with artificial scaffold protein. Front Bioeng Biotechnol 2023; 11:1251298. [PMID: 37711449 PMCID: PMC10497880 DOI: 10.3389/fbioe.2023.1251298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 08/15/2023] [Indexed: 09/16/2023] Open
Abstract
Introduction: Trehalose is a significant rare sugar known for its stable properties and ability to protect biomolecules from environmental factors. Methods: In this study, we present a novel approach utilizing a scaffold protein-mediated assembly method for the formation of a trehalose bi-enzyme complex. This complex consists of maltooligosyltrehalose synthase (MTSase) and maltooligosyltrehalose trehalohydrolase (MTHase), which work in tandem to catalyze the substrate and enhance the overall catalytic efficiency. Utilizing the specific interaction between cohesin and dockerin, this study presents the implementation of an assembly, an analysis of its efficiency, and an exploration of strategies to enhance enzyme utilization through the construction of a bi-enzyme complex under optimal conditions in vitro. Results and Discussion: The bi-enzyme complex demonstrated a trehalose production level 1.5 times higher than that of the free enzyme mixture at 40 h, with a sustained upward trend. Compared to free enzyme mixtures, the adoption of a scaffold protein-mediated bi-enzyme complex may improve cascade reactions and catalytic effects, thus presenting promising prospects.
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Affiliation(s)
- Xiangyi Wang
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Yi Jiang
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Hongling Liu
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Xinyi Zhang
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Haibo Yuan
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Di Huang
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
| | - Tengfei Wang
- State Key Laboratory of Biobased Material and Green Papermaking (LBMP), Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
- Key Laboratory of Shandong Microbial Engineering, School of Bioengineering, Shandong Academy of Sciences, Qilu University of Technology, Jinan, Shandong, China
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Abstract
This article comments on: Tian L, Liu L, Xu S, Deng R, Wu P, Jiang H, Wu G, Chen Y. 2022. A d-pinitol transporter, LjPLT11, regulates plant growth and nodule development in Lotus japonicus. Journal of Experimental Botany 73, 351–365.
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Affiliation(s)
- Philip S Poole
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Raphael Ledermann
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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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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Albicoro FJ, Draghi WO, Martini MC, Salas ME, Torres Tejerizo GA, Lozano MJ, López JL, Vacca C, Cafiero JH, Pistorio M, Bednarz H, Meier D, Lagares A, Niehaus K, Becker A, Del Papa MF. The two-component system ActJK is involved in acid stress tolerance and symbiosis in Sinorhizobium meliloti. J Biotechnol 2021; 329:80-91. [PMID: 33539896 DOI: 10.1016/j.jbiotec.2021.01.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 12/31/2020] [Accepted: 01/08/2021] [Indexed: 01/25/2023]
Abstract
The nitrogen-fixing α-proteobacterium Sinorhizobium meliloti genome codifies at least 50 response regulator (RR) proteins mediating different and, in many cases, unknown processes. RR-mutant library screening allowed us to identify genes potentially implicated in survival to acid conditions. actJ mutation resulted in a strain with reduced growth rate under mildly acidic conditions as well as a lower capacity to tolerate a sudden shift to lethal acidic conditions compared with the parental strain. Mutation of the downstream gene actK, which encodes for a histidine kinase, showed a similar phenotype in acidic environments suggesting a functional two-component system. Interestingly, even though nodulation kinetics, quantity, and macroscopic morphology of Medicago sativa nodules were not affected in actJ and actK mutants, ActK was required to express the wild-type nitrogen fixation phenotype and ActJK was necessary for full bacteroid development and nodule occupancy. The actJK regulatory system presented here provides insights into an evolutionary process in rhizobium adaptation to acidic environments and suggests that actJK-controlled functions are crucial for optimal symbiosis development.
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Affiliation(s)
- Francisco J Albicoro
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Walter O Draghi
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - María C Martini
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - María E Salas
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - G A Torres Tejerizo
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mauricio J Lozano
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - José L López
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carolina Vacca
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Juan H Cafiero
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mariano Pistorio
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Hanna Bednarz
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany
| | - Doreen Meier
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany; LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany
| | - Antonio Lagares
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Karsten Niehaus
- CeBiTec, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany; Faculty of Biology, Philipps-Universität Marburg, Marburg, Germany
| | - M F Del Papa
- Instituto de Biotecnología y Biología Molecular -CONICET CCT La Plata Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
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Paraburkholderia phymatum STM815 σ54 Controls Utilization of Dicarboxylates, Motility, and T6SS-b Expression. NITROGEN 2020. [DOI: 10.3390/nitrogen1020008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rhizobia have two major life styles, one as free-living bacteria in the soil, and the other as bacteroids within the root/stem nodules of host legumes where they convert atmospheric nitrogen into ammonia. In the soil, rhizobia have to cope with changing and sometimes stressful environmental conditions, such as nitrogen limitation. In the beta-rhizobial strain Paraburkholderia phymatum STM815, the alternative sigma factor σ54 (or RpoN) has recently been shown to control nitrogenase activity during symbiosis with Phaseolus vulgaris. In this study, we determined P. phymatum’s σ54 regulon under nitrogen-limited free-living conditions. Among the genes significantly downregulated in the absence of σ54, we found a C4-dicarboxylate carrier protein (Bphy_0225), a flagellar biosynthesis cluster (Bphy_2926-64), and one of the two type VI secretion systems (T6SS-b) present in the P. phymatum STM815 genome (Bphy_5978-97). A defined σ54 mutant was unable to grow on C4 dicarboxylates as sole carbon source and was less motile compared to the wild-type strain. Both defects could be complemented by introducing rpoNin trans. Using promoter reporter gene fusions, we also confirmed that the expression of the T6SS-b cluster is regulated by σ54. Accordingly, we show that σ54 affects in vitro competitiveness of P. phymatum STM815 against Paraburkholderia diazotrophica.
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Greffe VRG, Michiels J. Desiccation-induced cell damage in bacteria and the relevance for inoculant production. Appl Microbiol Biotechnol 2020; 104:3757-3770. [PMID: 32170388 DOI: 10.1007/s00253-020-10501-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 02/18/2020] [Accepted: 02/26/2020] [Indexed: 12/21/2022]
Abstract
Plant growth-promoting bacteria show great potential for use in agriculture although efficient application remains challenging to achieve. Cells often lose viability during inoculant production and application, jeopardizing the efficacy of the inoculant. Since desiccation has been documented to be the primary stress factor affecting the decrease in survival, obtaining xerotolerance in plant growth-promoting bacteria is appealing. The molecular damage that occurs by drying bacteria has been broadly investigated, although a complete view is still lacking due to the complex nature of the process. Mechanic, structural, and metabolic changes that occur as a result of water depletion may potentially afflict lethal damage to membranes, DNA, and proteins. Bacteria respond to these harsh conditions by increasing production of exopolysaccharides, changing composition of the membrane, improving the stability of proteins, reducing oxidative stress, and repairing DNA damage. This review provides insight into the complex nature of desiccation stress in bacteria in order to facilitate strategic choices to improve survival and shelf life of newly developed inoculants. KEY POINTS: Desiccation-induced damage affects most major macromolecules in bacteria. Most bacteria are not xerotolerant despite multiple endogenous adaption mechanisms. Sensitivity to drying severely hampers inoculant quality.
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Affiliation(s)
- Vincent Robert Guy Greffe
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium.,VIB Center for Microbiology, Flanders Institute for Biotechnology, Leuven, Belgium
| | - Jan Michiels
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium. .,VIB Center for Microbiology, Flanders Institute for Biotechnology, Leuven, Belgium.
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Abstract
Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress. Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.
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Ledermann R, Bartsch I, Müller B, Wülser J, Fischer HM. A Functional General Stress Response of Bradyrhizobium diazoefficiens Is Required for Early Stages of Host Plant Infection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:537-547. [PMID: 29278144 DOI: 10.1094/mpmi-11-17-0284-r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Phylogenetically diverse bacteria respond to various stress conditions by mounting a general stress response (GSR) resulting in the induction of protection or damage repair functions. In α-proteobacteria, the GSR is induced by a regulatory cascade consisting of the extracytoplasmic function (ECF) σ factor σEcfG, its anti-σ factor NepR, and the anti-anti-σ factor PhyR. We have reported previously that σEcfG and PhyR of Bradyrhizobium diazoefficiens (formerly named Bradyrhizobium japonicum), the nitrogen-fixing root nodule symbiont of soybean and related legumes, are required for efficient symbiosis; however, the precise role of the GSR remained undefined. Here, we analyze the symbiotic defects of a B. diazoefficiens mutant lacking σEcfG by comparing distinct infection stages of enzymatically or fluorescently tagged wild-type and mutant bacteria. Although root colonization and root hair curling were indistinguishable, the mutant was not competitive, and showed delayed development of emerging nodules and only a few infection threads. Consequently, many of the mutant-induced nodules were aborted, empty, or partially colonized. Congruent with these results, we found that σEcfG was active in bacteria present in root-hair-entrapped microcolonies and infection threads but not in root-associated bacteria and nitrogen-fixing bacteroids. We conclude that GSR-controlled functions are crucial for synchronization of infection thread formation, colonization, and nodule development.
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Affiliation(s)
- Raphael Ledermann
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Ilka Bartsch
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Barbara Müller
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Janine Wülser
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Hans-Martin Fischer
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
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Luebke JL, Eaton DS, Sachleben JR, Crosson S. Allosteric control of a bacterial stress response system by an anti-σ factor. Mol Microbiol 2018; 107:164-179. [PMID: 29052909 PMCID: PMC5760481 DOI: 10.1111/mmi.13868] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2017] [Indexed: 11/28/2022]
Abstract
Bacterial signal transduction systems commonly use receiver (REC) domains, which regulate adaptive responses to the environment as a function of their phosphorylation state. REC domains control cell physiology through diverse mechanisms, many of which remain understudied. We have defined structural features that underlie activation of the multi-domain REC protein, PhyR, which functions as an anti-anti-σ factor and regulates transcription of genes required for stress adaptation and host-microbe interactions in Alphaproteobacteria. Though REC phosphorylation is necessary for PhyR function in vivo, we did not detect expected changes in inter-domain interactions upon phosphorylation by solution X-ray scattering. We sought to understand this result by defining additional molecular requirements for PhyR activation. We uncovered specific interactions between unphosphorylated PhyR and an intrinsically disordered region (IDR) of the anti-σ factor, NepR, by solution NMR spectroscopy. Our data support a model whereby nascent NepR(IDR)-PhyR interactions and REC phosphorylation coordinately impart the free energy to shift PhyR to an open, active conformation that binds and inhibits NepR. This mechanism ensures PhyR is activated only when NepR and an activating phosphoryl signal are present. Our study provides new structural understanding of the molecular regulatory logic underlying a conserved environmental response system.
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Affiliation(s)
- Justin L. Luebke
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
| | - Daniel S. Eaton
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
| | - Joseph R. Sachleben
- Biomolecular NMR Core Facility, Biological Sciences Division, The University of Chicago, Chicago, Illinois, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, USA
- Department of Microbiology, The University of Chicago, Chicago, Illinois, USA
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Robledo M, Peregrina A, Millán V, García-Tomsig NI, Torres-Quesada O, Mateos PF, Becker A, Jiménez-Zurdo JI. A conserved α-proteobacterial small RNA contributes to osmoadaptation and symbiotic efficiency of rhizobia on legume roots. Environ Microbiol 2017; 19:2661-2680. [PMID: 28401641 DOI: 10.1111/1462-2920.13757] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/05/2017] [Accepted: 04/05/2017] [Indexed: 02/02/2023]
Abstract
Small non-coding RNAs (sRNAs) are expected to have pivotal roles in the adaptive responses underlying symbiosis of nitrogen-fixing rhizobia with legumes. Here, we provide primary insights into the function and activity mechanism of the Sinorhizobium meliloti trans-sRNA NfeR1 (Nodule Formation Efficiency RNA). Northern blot probing and transcription tracking with fluorescent promoter-reporter fusions unveiled high nfeR1 expression in response to salt stress and throughout the symbiotic interaction. The strength and differential regulation of nfeR1 transcription are conferred by a motif, which is conserved in nfeR1 promoter regions in α-proteobacteria. NfeR1 loss-of-function compromised osmoadaptation of free-living bacteria, whilst causing misregulation of salt-responsive genes related to stress adaptation, osmolytes catabolism and membrane trafficking. Nodulation tests revealed that lack of NfeR1 affected competitiveness, infectivity, nodule development and symbiotic efficiency of S. meliloti on alfalfa roots. Comparative computer predictions and a genetic reporter assay evidenced a redundant role of three identical NfeR1 unpaired anti Shine-Dalgarno motifs for targeting and downregulation of translation of multiple mRNAs from transporter genes. Our data provide genetic evidence of the hyperosmotic conditions of the endosymbiotic compartments. NfeR1-mediated gene regulation in response to this cue could contribute to coordinate nutrient uptake with the metabolic reprogramming concomitant to symbiotic transitions.
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Affiliation(s)
- Marta Robledo
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Alexandra Peregrina
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Vicenta Millán
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Natalia I García-Tomsig
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Omar Torres-Quesada
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
| | - Pedro F Mateos
- Departamento de Microbiología y Genética and CIALE, Edificio Departamental, Campus Miguel de Unamuno, Universidad de Salamanca, 37007 Salamanca, Spain
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology and Faculty of Biology, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - José I Jiménez-Zurdo
- Grupo de Ecología Genética de la Rizosfera, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain
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11
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Zhang Y, Smallbone LA, diCenzo GC, Morton R, Finan TM. Loss of malic enzymes leads to metabolic imbalance and altered levels of trehalose and putrescine in the bacterium Sinorhizobium meliloti. BMC Microbiol 2016; 16:163. [PMID: 27456220 PMCID: PMC4960864 DOI: 10.1186/s12866-016-0780-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 07/15/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malic enzymes decarboxylate the tricarboxylic acid (TCA) cycle intermediate malate to the glycolytic end-product pyruvate and are well positioned to regulate metabolic flux in central carbon metabolism. Despite the wide distribution of these enzymes, their biological roles are unclear in part because the reaction catalyzed by these enzymes can be by-passed by other pathways. The N2-fixing alfalfa symbiont Sinorhizobium meliloti contains both a NAD(P)-malic enzyme (DME) and a separate NADP-malic enzyme (TME) and to help understand the role of these enzymes, we investigated growth, metabolomic, and transcriptional consequences resulting from loss of these enzymes in free-living cells. RESULTS Loss of DME, TME, or both enzymes had no effect on growth with the glycolytic substrate, glucose. In contrast, the dme mutants, but not tme, grew slowly on the gluconeogenic substrate succinate and this slow growth was further reduced upon the addition of glucose. The dme mutant strains incubated with succinate accumulated trehalose and hexose sugar phosphates, secreted malate, and relative to wild-type, these cells had moderately increased transcription of genes involved in gluconeogenesis and pathways that divert metabolites away from the TCA cycle. While tme mutant cells grew at the same rate as wild-type on succinate, they accumulated the compatible solute putrescine. CONCLUSIONS NAD(P)-malic enzyme (DME) of S. meliloti is required for efficient metabolism of succinate via the TCA cycle. In dme mutants utilizing succinate, malate accumulates and is excreted and these cells appear to increase metabolite flow via gluconeogenesis with a resulting increase in the levels of hexose-6-phosphates and trehalose. For cells utilizing succinate, TME activity alone appeared to be insufficient to produce the levels of pyruvate required for efficient TCA cycle metabolism. Putrescine was found to accumulate in tme cells growing with succinate, and whether this is related to altered levels of NADPH requires further investigation.
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Affiliation(s)
- Ye Zhang
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada.,College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Laura Anne Smallbone
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada
| | - George C diCenzo
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada
| | - Richard Morton
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada
| | - Turlough M Finan
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada.
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12
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Reyes-Pérez A, Vargas MDC, Hernández M, Aguirre-von-Wobeser E, Pérez-Rueda E, Encarnacion S. Transcriptomic analysis of the process of biofilm formation in Rhizobium etli CFN42. Arch Microbiol 2016; 198:847-60. [PMID: 27226009 DOI: 10.1007/s00203-016-1241-5] [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] [Received: 12/09/2015] [Revised: 03/17/2016] [Accepted: 05/06/2016] [Indexed: 12/19/2022]
Abstract
Organisms belonging to the genus Rhizobium colonize leguminous plant roots and establish a mutually beneficial symbiosis. Biofilms are structured ecosystems in which microbes are embedded in a matrix of extracellular polymeric substances, and their development is a multistep process. The biofilm formation processes of R. etli CFN42 were analyzed at an early (24-h incubation) and mature stage (72 h), comparing cells in the biofilm with cells remaining in the planktonic stage. A genome-wide microarray analysis identified 498 differentially regulated genes, implying that expression of ~8.3 % of the total R. etli gene content was altered during biofilm formation. In biofilms-attached cells, genes encoding proteins with diverse functions were overexpressed including genes involved in membrane synthesis, transport and chemotaxis, repression of flagellin synthesis, as well as surface components (particularly exopolysaccharides and lipopolysaccharides), in combination with the presence of activators or stimulators of N-acyl-homoserine lactone synthesis This suggests that R. etli is able to sense surrounding environmental conditions and accordingly regulate the transition from planktonic and biofilm growth. In contrast, planktonic cells differentially expressed genes associated with transport, motility (flagellar and twitching) and inhibition of exopolysaccharide synthesis. To our knowledge, this is the first report of nodulation and nitrogen assimilation-related genes being involved in biofilm formation in R. etli. These results contribute to the understanding of the physiological changes involved in biofilm formation by bacteria.
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Affiliation(s)
- Agustín Reyes-Pérez
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos, Mexico.,Facultad de Ciencias, Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Apartado Postal 70-153, C.P. 0415, Cuernavaca, D.F., Mexico.,Centro de Investigación en Dinámica Celular, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, 62209, Mexico
| | - María Del Carmen Vargas
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos, Mexico
| | - Magdalena Hernández
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos, Mexico
| | - Eneas Aguirre-von-Wobeser
- Red de Estudios Moleculares Avanzados, Instituto de Ecología, A. C. Coatepec 351, El Haya, Xalapa, Veracruz, Mexico
| | - Ernesto Pérez-Rueda
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, UNAM, Av. Universidad s/n, Col. Chamilpa, Cuernavaca, Morelos, Mexico
| | - Sergio Encarnacion
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos, Mexico.
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13
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Abstract
The Alphaproteobacteria uniquely integrate features of two-component signal transduction and alternative σ factor regulation to control transcription of genes that ensure growth and survival across a range of stress conditions. Research over the past decade has led to the discovery of the key molecular players of this general stress response (GSR) system, including the sigma factor σ(EcfG), its anti-σ factor NepR, and the anti-anti-σ factor PhyR. The central molecular event of GSR activation entails aspartyl phosphorylation of PhyR, which promotes its binding to NepR and thereby releases σ(EcfG) to associate with RNAP and direct transcription. Recent studies are providing a new understanding of complex, multilayered sensory networks that activate and repress this central protein partner switch. This review synthesizes our structural and functional understanding of the core GSR regulatory proteins and highlights emerging data that are defining the systems that regulate GSR transcription in a variety of species.
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Affiliation(s)
- Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Julien Herrou
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Jonathan Willett
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
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14
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Unraveling the universe of small RNA regulators in the legume symbiont Sinorhizobium meliloti. Symbiosis 2015. [DOI: 10.1007/s13199-015-0345-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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15
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The general stress response in Alphaproteobacteria. Trends Microbiol 2015; 23:164-71. [DOI: 10.1016/j.tim.2014.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 11/18/2022]
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16
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A putative bifunctional histidine kinase/phosphatase of the HWE family exerts positive and negative control on the Sinorhizobium meliloti general stress response. J Bacteriol 2014; 196:2526-35. [PMID: 24794560 DOI: 10.1128/jb.01623-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The EcfG-type sigma factor RpoE2 is the regulator of the general stress response in Sinorhizobium meliloti. RpoE2 activity is negatively regulated by two NepR-type anti-sigma factors (RsiA1/A2), themselves under the control of two anti-anti-sigma factors (RsiB1/B2) belonging to the PhyR family of response regulators. The current model of RpoE2 activation suggests that in response to stress, RsiB1/B2 are activated by phosphorylation of an aspartate residue in their receiver domain. Once activated, RsiB1/B2 become able to interact with the anti-sigma factors and release RpoE2, which can then associate with the RNA polymerase to transcribe its target genes. The purpose of this work was to identify and characterize proteins involved in controlling the phosphorylation status of RsiB1/B2. Using in vivo approaches, we show that the putative histidine kinase encoded by the rsiC gene (SMc01507), located downstream from rpoE2, is able to both positively and negatively regulate the general stress response. In addition, our data suggest that the negative action of RsiC results from inhibition of RsiB1/B2 phosphorylation. From these observations, we propose that RsiC is a bifunctional histidine kinase/phosphatase responsible for RsiB1/B2 phosphorylation or dephosphorylation in the presence or absence of stress, respectively. Two proteins were previously proposed to control PhyR phosphorylation in Caulobacter crescentus and Sphingomonas sp. strain FR1. However, these proteins contain a Pfam:HisKA_2 domain of dimerization and histidine phosphotransfer, whereas S. meliloti RsiC harbors a Pfam:HWE_HK domain instead. Therefore, this is the first report of an HWE_HK-containing protein controlling the general stress response in Alphaproteobacteria.
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Torres-Quesada O, Reinkensmeier J, Schlüter JP, Robledo M, Peregrina A, Giegerich R, Toro N, Becker A, Jiménez-Zurdo JI. Genome-wide profiling of Hfq-binding RNAs uncovers extensive post-transcriptional rewiring of major stress response and symbiotic regulons in Sinorhizobium meliloti. RNA Biol 2014; 11:563-79. [PMID: 24786641 DOI: 10.4161/rna.28239] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The RNA chaperone Hfq is a global post-transcriptional regulator in bacteria. Here, we used RNAseq to analyze RNA populations from the legume symbiont Sinorhizobium meliloti that were co-immunoprecipitated (CoIP-RNA) with a FLAG-tagged Hfq in five growth/stress conditions. Hfq-bound transcripts (1315) were largely identified in stressed bacteria and derived from small RNAs (sRNAs), both trans-encoded (6.4%) and antisense (asRNAs; 6.3%), and mRNAs (86%). Pull-down with Hfq recovered a small proportion of annotated S. meliloti sRNAs (14% of trans-sRNAs and 2% of asRNAs) suggesting a discrete impact of this protein in sRNA pathways. Nonetheless, Hfq selectively stabilized CoIP-enriched sRNAs, anticipating that these interactions are functionally significant. Transcription of 26 Hfq-bound sRNAs was predicted to occur from promoters recognized by the major stress σ factors σ(E2) or σ(H1/2). Recovery rates of sRNAs in each of the CoIP-RNA libraries suggest a large impact of Hfq-assisted riboregulation in S. meliloti osmoadaptation. Hfq directly targeted 18% of the predicted S. meliloti mRNAs, which encode functionally diverse proteins involved in transport and metabolism, σ(E2)-dependent stress responses, quorum sensing, flagella biosynthesis, ribosome, and membrane assembly or symbiotic nitrogen fixation. Canonical targeting of the 5' regions of two of the ABC transporter mRNAs by the homologous Hfq-binding AbcR1 and AbcR2 sRNAs leading to inhibition of protein synthesis was confirmed in vivo. We therefore provide a comprehensive resource for the systems-level deciphering of hitherto unexplored S. meliloti stress and symbiotic post-transcriptional regulons and the identification of Hfq-dependent sRNA-mRNA regulatory pairs.
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Affiliation(s)
- Omar Torres-Quesada
- Grupo de Ecología Genética de la Rizosfera; Estación Experimental del Zaidín; Consejo Superior de Investigaciones Científicas; CSIC, Granada, Spain
| | - Jan Reinkensmeier
- Center for Biotechnology (CeBiTec); Bielefeld University; Bielefeld, Germany
| | - Jan-Philip Schlüter
- LOEWE Center for Synthetic Microbiology (SYNMIKRO) and Department of Biology; Philipps-Universität Marburg; Marburg, Germany
| | - Marta Robledo
- LOEWE Center for Synthetic Microbiology (SYNMIKRO) and Department of Biology; Philipps-Universität Marburg; Marburg, Germany
| | - Alexandra Peregrina
- Grupo de Ecología Genética de la Rizosfera; Estación Experimental del Zaidín; Consejo Superior de Investigaciones Científicas; CSIC, Granada, Spain
| | - Robert Giegerich
- Center for Biotechnology (CeBiTec); Bielefeld University; Bielefeld, Germany
| | - Nicolás Toro
- Grupo de Ecología Genética de la Rizosfera; Estación Experimental del Zaidín; Consejo Superior de Investigaciones Científicas; CSIC, Granada, Spain
| | - Anke Becker
- LOEWE Center for Synthetic Microbiology (SYNMIKRO) and Department of Biology; Philipps-Universität Marburg; Marburg, Germany
| | - Jose I Jiménez-Zurdo
- Grupo de Ecología Genética de la Rizosfera; Estación Experimental del Zaidín; Consejo Superior de Investigaciones Científicas; CSIC, Granada, Spain
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Sallet E, Roux B, Sauviac L, Jardinaud MF, Carrère S, Faraut T, de Carvalho-Niebel F, Gouzy J, Gamas P, Capela D, Bruand C, Schiex T. Next-generation annotation of prokaryotic genomes with EuGene-P: application to Sinorhizobium meliloti 2011. DNA Res 2013; 20:339-54. [PMID: 23599422 PMCID: PMC3738161 DOI: 10.1093/dnares/dst014] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The availability of next-generation sequences of transcripts from prokaryotic organisms offers the opportunity to design a new generation of automated genome annotation tools not yet available for prokaryotes. In this work, we designed EuGene-P, the first integrative prokaryotic gene finder tool which combines a variety of high-throughput data, including oriented RNA-Seq data, directly into the prediction process. This enables the automated prediction of coding sequences (CDSs), untranslated regions, transcription start sites (TSSs) and non-coding RNA (ncRNA, sense and antisense) genes. EuGene-P was used to comprehensively and accurately annotate the genome of the nitrogen-fixing bacterium Sinorhizobium meliloti strain 2011, leading to the prediction of 6308 CDSs as well as 1876 ncRNAs. Among them, 1280 appeared as antisense to a CDS, which supports recent findings that antisense transcription activity is widespread in bacteria. Moreover, 4077 TSSs upstream of protein-coding or non-coding genes were precisely mapped providing valuable data for the study of promoter regions. By looking for RpoE2-binding sites upstream of annotated TSSs, we were able to extend the S. meliloti RpoE2 regulon by ∼3-fold. Altogether, these observations demonstrate the power of EuGene-P to produce a reliable and high-resolution automatic annotation of prokaryotic genomes.
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Affiliation(s)
- Erika Sallet
- INRA, Laboratoire des Interactions Plantes-Microorganismes-LIPM, UMR 441, Castanet-Tolosan F-31326, France
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19
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Schlüter JP, Reinkensmeier J, Barnett MJ, Lang C, Krol E, Giegerich R, Long SR, Becker A. Global mapping of transcription start sites and promoter motifs in the symbiotic α-proteobacterium Sinorhizobium meliloti 1021. BMC Genomics 2013; 14:156. [PMID: 23497287 PMCID: PMC3616915 DOI: 10.1186/1471-2164-14-156] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 02/12/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sinorhizobium meliloti is a soil-dwelling α-proteobacterium that possesses a large, tripartite genome and engages in a nitrogen fixing symbiosis with its plant hosts. Although much is known about this important model organism, global characterization of genetic regulatory circuits has been hampered by a lack of information about transcription and promoters. RESULTS Using an RNAseq approach and RNA populations representing 16 different growth and stress conditions, we comprehensively mapped S. meliloti transcription start sites (TSS). Our work identified 17,001 TSS that we grouped into six categories based on the genomic context of their transcripts: mRNA (4,430 TSS assigned to 2,657 protein-coding genes), leaderless mRNAs (171), putative mRNAs (425), internal sense transcripts (7,650), antisense RNA (3,720), and trans-encoded sRNAs (605). We used this TSS information to identify transcription factor binding sites and putative promoter sequences recognized by seven of the 15 known S. meliloti σ factors σ70, σ54, σH1, σH2, σE1, σE2, and σE9). Altogether, we predicted 2,770 new promoter sequences, including 1,302 located upstream of protein coding genes and 722 located upstream of antisense RNA or trans-encoded sRNA genes. To validate promoter predictions for targets of the general stress response σ factor, RpoE2 (σE2), we identified rpoE2-dependent genes using microarrays and confirmed TSS for a subset of these by 5' RACE mapping. CONCLUSIONS By identifying TSS and promoters on a global scale, our work provides a firm foundation for the continued study of S. meliloti gene expression with relation to gene organization, σ factors and other transcription factors, and regulatory RNAs.
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Affiliation(s)
- Jan-Philip Schlüter
- Institute of Biology III, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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20
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Bastiat B, Sauviac L, Picheraux C, Rossignol M, Bruand C. Sinorhizobium meliloti sigma factors RpoE1 and RpoE4 are activated in stationary phase in response to sulfite. PLoS One 2012; 7:e50768. [PMID: 23226379 PMCID: PMC3511301 DOI: 10.1371/journal.pone.0050768] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/24/2012] [Indexed: 12/02/2022] Open
Abstract
Rhizobia are soil bacteria able to establish a nitrogen-fixing symbiosis with legume plants. Both in soil and in planta, rhizobia spend non-growing periods resembling the stationary phase of in vitro-cultured bacteria. The primary objective of this work was to better characterize gene regulation in this biologically relevant growth stage in Sinorhizobium meliloti. By a tap-tag/mass spectrometry approach, we identified five sigma factors co-purifying with the RNA polymerase in stationary phase: the general stress response regulator RpoE2, the heat shock sigma factor RpoH2, and three extra-cytoplasmic function sigma factors (RpoE1, RpoE3 and RpoE4) belonging to the poorly characterized ECF26 subgroup. We then showed that RpoE1 and RpoE4 i) are activated upon metabolism of sulfite-generating compounds (thiosulfate and taurine), ii) display overlapping regulatory activities, iii) govern a dedicated sulfite response by controlling expression of the sulfite dehydrogenase SorT, iv) are activated in stationary phase, likely as a result of endogenous sulfite generation during bacterial growth. We showed that SorT is required for optimal growth of S. meliloti in the presence of sulfite, suggesting that the response governed by RpoE1 and RpoE4 may be advantageous for bacteria in stationary phase either by providing a sulfite detoxification function or by contributing to energy production through sulfite respiration. This paper therefore reports the first characterization of ECF26 sigma factors, the first description of sigma factors involved in control of sulphur metabolism, and the first indication that endogenous sulfite may act as a signal for regulation of gene expression upon entry of bacteria in stationary phase.
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Affiliation(s)
- Bénédicte Bastiat
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
| | - Laurent Sauviac
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
| | - Carole Picheraux
- Fédération de Recherche 3450, Agrobiosciences, Interactions et Biodiversités, Plateforme Protéomique Génopole Toulouse Midi-Pyrénées, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, Toulouse, France
- Université Paul Sabatier, Université de Toulouse, Toulouse, France
| | - Michel Rossignol
- Fédération de Recherche 3450, Agrobiosciences, Interactions et Biodiversités, Plateforme Protéomique Génopole Toulouse Midi-Pyrénées, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, Toulouse, France
- Université Paul Sabatier, Université de Toulouse, Toulouse, France
| | - Claude Bruand
- INRA, Laboratoire des Interactions Plantes-Microorganismes, UMR441, Castanet-Tolosan, France
- Centre National de la Recherche Scientifique, Laboratoire des Interactions Plantes-Microorganismes, UMR2594, Castanet-Tolosan, France
- * E-mail:
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21
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Dual RpoH sigma factors and transcriptional plasticity in a symbiotic bacterium. J Bacteriol 2012; 194:4983-94. [PMID: 22773790 DOI: 10.1128/jb.00449-12] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Sinorhizobium meliloti can live as a soil saprophyte and can engage in a nitrogen-fixing symbiosis with plant roots. To succeed in such diverse environments, the bacteria must continually adjust gene expression. Transcriptional plasticity in eubacteria is often mediated by alternative sigma (σ) factors interacting with core RNA polymerase. The S. meliloti genome encodes 14 of these alternative σ factors, including two putative RpoH ("heat shock") σ factors. We used custom Affymetrix symbiosis chips to characterize the global transcriptional response of S. meliloti rpoH1, rpoH2, and rpoH1 rpoH2 mutants during heat shock and stationary-phase growth. Under these conditions, expression of over 300 genes is dependent on rpoH1 and rpoH2. We mapped transcript start sites of 69 rpoH-dependent genes using 5' RACE (5' rapid amplification of cDNA ends), which allowed us to determine putative RpoH1-dependent, RpoH2-dependent, and dual-promoter (RpoH1- and RpoH2-dependent) consensus sequences that were each used to search the genome for other potential direct targets of RpoH. The inferred S. meliloti RpoH promoter consensus sequences share features of Escherichia coli RpoH promoters but lack extended -10 motifs.
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22
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Stockwell SB, Reutimann L, Guerinot ML. A role for Bradyrhizobium japonicum ECF16 sigma factor EcfS in the formation of a functional symbiosis with soybean. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:119-28. [PMID: 21879796 DOI: 10.1094/mpmi-07-11-0188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Alternative sigma (σ) factors, proteins that recruit RNA polymerase core enzyme to target promoters, are one mechanism by which bacteria transcriptionally regulate groups of genes in response to environmental stimuli. A class of σ(70) proteins, termed extracytoplasmic function (ECF) σ factors, are involved in cellular processes such as bacterial stress responses and virulence. Here, we describe an ECF16 σ factor, EcfS (Blr4928) from the gram-negative soil bacterium Bradyrhizobium japonicum USDA110, that plays a critical role in the establishment of a functional symbiosis with soybean. Nonpolar insertional mutants of ecfS form immature nodules that do not fix nitrogen, a defect that can be successfully complemented by expression of ecfS. Overexpression of the cocistronic gene, tmrS (blr4929), phenocopies the ecfS mutant in planta and, therefore, we propose that TmrS is a negative regulator of EcfS, a determination consistent with the prediction that it encodes an anti-σ factor. Microarray analysis of the ecfS mutant and tmrS overexpressor was used to identify 40 transcripts misregulated in both strains. These transcripts primarily encode proteins of unknown and transport-related functions and may provide insights into the symbiotic defect in these strains.
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MESH Headings
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Bradyrhizobium/genetics
- Bradyrhizobium/metabolism
- Bradyrhizobium/physiology
- DNA, Complementary/genetics
- Gene Expression/genetics
- Gene Expression Profiling
- Gene Expression Regulation, Bacterial/genetics
- Genes, Bacterial/genetics
- Genetic Complementation Test
- Mutagenesis, Insertional
- Nitrogen Fixation
- Oligonucleotide Array Sequence Analysis
- Phenotype
- Plant Leaves/microbiology
- RNA, Bacterial/genetics
- RNA, Messenger/genetics
- Root Nodules, Plant/microbiology
- Root Nodules, Plant/ultrastructure
- Sigma Factor/genetics
- Sigma Factor/metabolism
- Glycine max/microbiology
- Glycine max/ultrastructure
- Stress, Physiological
- Symbiosis
- Transcription, Genetic
- Transcriptome
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Affiliation(s)
- S B Stockwell
- Biological Sciences Department, Dartmouth College, Hanover, NH, USA.
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23
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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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Brique A, Devassine J, Pilard S, Cailleu D, Gosselin I. Osmoregulated trehalose-derived oligosaccharides inSinorhizobium meliloti. FEBS Lett 2010; 584:3661-6. [DOI: 10.1016/j.febslet.2010.07.047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 07/21/2010] [Accepted: 07/26/2010] [Indexed: 11/29/2022]
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25
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Fernandez-Aunión C, Hamouda TB, Iglesias-Guerra F, Argandoña M, Reina-Bueno M, Nieto JJ, Aouani ME, Vargas C. Biosynthesis of compatible solutes in rhizobial strains isolated from Phaseolus vulgaris nodules in Tunisian fields. BMC Microbiol 2010; 10:192. [PMID: 20633304 PMCID: PMC2918589 DOI: 10.1186/1471-2180-10-192] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Accepted: 07/16/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Associated with appropriate crop and soil management, inoculation of legumes with microbial biofertilizers can improve food legume yield and soil fertility and reduce pollution by inorganic fertilizers. Rhizospheric bacteria are subjected to osmotic stress imposed by drought and/or NaCl, two abiotic constraints frequently found in semi-arid lands. Osmostress response in bacteria involves the accumulation of small organic compounds called compatible solutes. Whereas most studies on rhizobial osmoadaptation have focussed on the model species Sinorhizobium meliloti, little is known on the osmoadaptive mechanisms used by native rhizobia, which are good sources of inoculants. In this work, we investigated the synthesis and accumulations of compatible solutes by four rhizobial strains isolated from root nodules of Phaseolus vulgaris in Tunisia, as well as by the reference strain Rhizobium tropici CIAT 899T. RESULTS The most NaCl-tolerant strain was A. tumefaciens 10c2, followed (in decreasing order) by R. tropici CIAT 899, R. leguminosarum bv. phaseoli 31c3, R. etli 12a3 and R. gallicum bv. phaseoli 8a3. 13C- and 1H-NMR analyses showed that all Rhizobium strains synthesized trehalose whereas A. tumefaciens 10c2 synthesized mannosucrose. Glutamate synthesis was also observed in R. tropici CIAT 899, R. leguminosarum bv. phaseoli 31c3 and A. tumefaciens 10c2. When added as a carbon source, mannitol was also accumulated by all strains. Accumulation of trehalose in R. tropici CIAT 899 and of mannosucrose in A. tumefaciens 10c2 was osmoregulated, suggesting their involvement in osmotolerance. The phylogenetic analysis of the otsA gene, encoding the trehalose-6-phosphate synthase, suggested the existence of lateral transfer events. In vivo 13C labeling experiments together with genomic analysis led us to propose the uptake and conversion pathways of different carbon sources into trehalose. Collaterally, the beta-1,2-cyclic glucan from R. tropici CIAT 899 was co-extracted with the cytoplasmic compatible solutes and its chemical structure was determined. CONCLUSIONS The soil bacteria analyzed in this work accumulated mainly disaccharides in response to NaCl stress. We could not find a direct correlation between the trehalose content of the rhizobial strains and their osmotolerance, suggesting that additional osmoadaptive mechanism should be operating in the most NaCl-tolerant strain R. tropici CIAT 899.
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