1
|
Syska C, Kiers A, Rancurel C, Bailly-Bechet M, Lipuma J, Alloing G, Garcia I, Dupont L. VapC10 toxin of the legume symbiont Sinorhizobium meliloti targets tRNASer and controls intracellular lifestyle. THE ISME JOURNAL 2024; 18:wrae015. [PMID: 38365913 PMCID: PMC10945364 DOI: 10.1093/ismejo/wrae015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/05/2024] [Accepted: 01/25/2024] [Indexed: 02/18/2024]
Abstract
The soil bacterium Sinorhizobium meliloti can establish a nitrogen-fixing symbiosis with the model legume Medicago truncatula. The rhizobia induce the formation of a specialized root organ called nodule, where they differentiate into bacteroids and reduce atmospheric nitrogen into ammonia. Little is known on the mechanisms involved in nodule senescence onset and in bacteroid survival inside the infected plant cells. Although toxin-antitoxin (TA) systems have been shown to promote intracellular survival within host cells in human pathogenic bacteria, their role in symbiotic bacteria was rarely investigated. S. meliloti encodes several TA systems, mainly of the VapBC family. Here we present the functional characterization, through a multidisciplinary approach, of the VapBC10 TA system of S. meliloti. Following a mapping by overexpression of an RNase in Escherichia coli (MORE) RNA-seq analysis, we demonstrated that the VapC10 toxin is an RNase that cleaves the anticodon loop of two tRNASer. Thereafter, a bioinformatics approach was used to predict VapC10 targets in bacteroids. This analysis suggests that toxin activation triggers a specific proteome reprogramming that could limit nitrogen fixation capability and viability of bacteroids. Accordingly, a vapC10 mutant induces a delayed senescence in nodules, associated to an enhanced bacteroid survival. VapBC10 TA system could contribute to S. meliloti adaptation to symbiotic lifestyle, in response to plant nitrogen status.
Collapse
Affiliation(s)
- Camille Syska
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | - Aurélie Kiers
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | - Corinne Rancurel
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | - Marc Bailly-Bechet
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | | | - Geneviève Alloing
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | - Isabelle Garcia
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| | - Laurence Dupont
- Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech (ISA), Sophia Antipolis 06903, France
| |
Collapse
|
2
|
Ide AA, Hernández VM, Medina-Aparicio L, Carcamo-Noriega E, Girard L, Hernández-Lucas I, Dunn MF. Genetic regulation, biochemical properties and physiological importance of arginase from Sinorhizobium meliloti. Microbiology (Reading) 2020; 166:484-497. [DOI: 10.1099/mic.0.000909] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In bacteria,l-arginine is a precursor of various metabolites and can serve as a source of carbon and/or nitrogen. Arginine catabolism by arginase, which hydrolyzes arginine tol-ornithine and urea, is common in nature but has not been studied in symbiotic nitrogen-fixing rhizobia. The genome of the alfalfa microsymbiontSinorhizobium meliloti1021 has two genes annotated as arginases,argI1(smc03091) andargI2(sma1711). Biochemical assays with purified ArgI1 and ArgI2 (as 6His-Sumo-tagged proteins) showed that only ArgI1 had detectable arginase activity. A 1021argI1null mutant lacked arginase activity and grew at a drastically reduced rate with arginine as sole nitrogen source. Wild-type growth and arginase activity were restored in theargI1mutant genetically complemented with a genomically integratedargI1gene. In the wild-type, arginase activity andargI1transcription were induced several fold by exogenous arginine. ArgI1 purified as a 6His-Sumo-tagged protein had its highestin vitroenzymatic activity at pH 7.5 with Ni2+as cofactor. The enzyme was also active with Mn2+and Co2+, both of which gave the enzyme the highest activities at a more alkaline pH. The 6His-Sumo-ArgI1 comprised three identical subunits based on the migration of the urea-dissociated protein in a native polyacrylamide gel. A Lrp-like regulator (smc03092) divergently transcribed fromargI1was required for arginase induction by arginine or ornithine. This regulator was designated ArgIR. Electrophoretic mobility shift assays showed that purified ArgIR bound to theargI1promoter in a region preceding the predictedargI1transcriptional start. Our results indicate that ArgI1 is the sole arginase inS. meliloti, that it contributes substantially to arginine catabolismin vivoand thatargI1induction by arginine is dependent on ArgIR.
Collapse
Affiliation(s)
- Alejandra Arteaga Ide
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Victor M. Hernández
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Liliana Medina-Aparicio
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Edson Carcamo-Noriega
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Lourdes Girard
- Programa de Biología de Sistemas y Biología Sintética, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Ismael Hernández-Lucas
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Michael F. Dunn
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| |
Collapse
|
3
|
Abstract
Rhizobia are α- and β-proteobacteria that form a symbiotic partnership with legumes, fixing atmospheric dinitrogen to ammonia and providing it to the plant. Oxygen regulation is key in this symbiosis. Fixation is performed by an oxygen-intolerant nitrogenase enzyme but requires respiration to meet its high energy demands. To satisfy these opposing constraints the symbiotic partners cooperate intimately, employing a variety of mechanisms to regulate and respond to oxygen concentration. During symbiosis rhizobia undergo significant changes in gene expression to differentiate into nitrogen-fixing bacteroids. Legumes host these bacteroids in specialized root organs called nodules. These generate a near-anoxic environment using an oxygen diffusion barrier, oxygen-binding leghemoglobin and control of mitochondria localization. Rhizobia sense oxygen using multiple interconnected systems which enable a finely-tuned response to the wide range of oxygen concentrations they experience when transitioning from soil to nodules. The oxygen-sensing FixL-FixJ and hybrid FixL-FxkR two-component systems activate at relatively high oxygen concentration and regulate fixK transcription. FixK activates the fixNOQP and fixGHIS operons producing a high-affinity terminal oxidase required for bacterial respiration in the microaerobic nodule. Additionally or alternatively, some rhizobia regulate expression of these operons by FnrN, an FNR-like oxygen-sensing protein. The final stage of symbiotic establishment is activated by the NifA protein, regulated by oxygen at both the transcriptional and protein level. A cross-species comparison of these systems highlights differences in their roles and interconnections but reveals common regulatory patterns and themes. Future work is needed to establish the complete regulon of these systems and identify other regulatory signals.
Collapse
Affiliation(s)
- Paul J Rutten
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Philip S Poole
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
4
|
Becerra-Rivera VA, Dunn MF. Polyamine biosynthesis and biological roles in rhizobia. FEMS Microbiol Lett 2019; 366:5476500. [DOI: 10.1093/femsle/fnz084] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 04/22/2019] [Indexed: 12/31/2022] Open
Abstract
ABSTRACTPolyamines are ubiquitous molecules containing two or more amino groups that fulfill varied and often essential physiological and regulatory roles in all organisms. In the symbiotic nitrogen-fixing bacteria known as rhizobia, putrescine and homospermidine are invariably produced while spermidine and norspermidine synthesis appears to be restricted to the alfalfa microsymbiont Sinorhizobium meliloti. Studies with rhizobial mutants deficient in the synthesis of one or more polyamines have shown that these compounds are important for growth, stress resistance, motility, exopolysaccharide production and biofilm formation. In this review, we describe these studies and examine how polyamines are synthesized and regulated in rhizobia.
Collapse
Affiliation(s)
- Victor A Becerra-Rivera
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas-Universidad Nacional Autónoma de México, Cuernavaca, Morelos, C.P. 62210, Mexico
| | - Michael F Dunn
- Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas-Universidad Nacional Autónoma de México, Cuernavaca, Morelos, C.P. 62210, Mexico
| |
Collapse
|
5
|
da-Silva JR, Alexandre A, Brígido C, Oliveira S. Can stress response genes be used to improve the symbiotic performance of rhizobia? AIMS Microbiol 2017; 3:365-382. [PMID: 31294167 PMCID: PMC6604987 DOI: 10.3934/microbiol.2017.3.365] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 05/16/2017] [Indexed: 12/31/2022] Open
Abstract
Rhizobia are soil bacteria able to form symbioses with legumes and fix atmospheric nitrogen, converting it into a form that can be assimilated by the plant. The biological nitrogen fixation is a possible strategy to reduce the environmental pollution caused by the use of chemical N-fertilizers in agricultural fields. Successful colonization of the host root by free-living rhizobia requires that these bacteria are able to deal with adverse conditions in the soil, in addition to stresses that may occur in their endosymbiotic life inside the root nodules. Stress response genes, such as otsAB, groEL, clpB, rpoH play an important role in tolerance of free-living rhizobia to different environmental conditions and some of these genes have been shown to be involved in the symbiosis. This review will focus on stress response genes that have been reported to improve the symbiotic performance of rhizobia with their host plants. For example, chickpea plants inoculated with a Mesorhizobium strain modified with extra copies of the groEL gene showed a symbiotic effectiveness approximately 1.5 fold higher than plants inoculated with the wild-type strain. Despite these promising results, more studies are required to obtain highly efficient and tolerant rhizobia strains, suitable for different edaphoclimatic conditions, to be used as field inoculants.
Collapse
Affiliation(s)
- José Rodrigo da-Silva
- Laboratório de Microbiologia do Solo, Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal
| | - Ana Alexandre
- Laboratório de Microbiologia do Solo, Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal
| | - Clarisse Brígido
- Laboratório de Microbiologia do Solo, Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal
| | - Solange Oliveira
- Laboratório de Microbiologia do Solo, Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal
| |
Collapse
|
6
|
Paço A, Brígido C, Alexandre A, Mateos PF, Oliveira S. The Symbiotic Performance of Chickpea Rhizobia Can Be Improved by Additional Copies of the clpB Chaperone Gene. PLoS One 2016; 11:e0148221. [PMID: 26845770 PMCID: PMC4741418 DOI: 10.1371/journal.pone.0148221] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 01/14/2016] [Indexed: 12/03/2022] Open
Abstract
The ClpB chaperone is known to be involved in bacterial stress response. Moreover, recent studies suggest that this protein has also a role in the chickpea-rhizobia symbiosis. In order to improve both stress tolerance and symbiotic performance of a chickpea microsymbiont, the Mesorhizobium mediterraneum UPM-Ca36T strain was genetically transformed with pPHU231 containing an extra-copy of the clpB gene. To investigate if the clpB-transformed strain displays an improved stress tolerance, bacterial growth was evaluated under heat and acid stress conditions. In addition, the effect of the extra-copies of the clpB gene in the symbiotic performance was evaluated using plant growth assays (hydroponic and pot trials). The clpB-transformed strain is more tolerant to heat shock than the strain transformed with pPHU231, supporting the involvement of ClpB in rhizobia heat shock tolerance. Both plant growth assays showed that ClpB has an important role in chickpea-rhizobia symbiosis. The nodulation kinetics analysis showed a higher rate of nodule appearance with the clpB-transformed strain. This strain also induced a greater number of nodules and, more notably, its symbiotic effectiveness increased ~60% at pH5 and 83% at pH7, compared to the wild-type strain. Furthermore, a higher frequency of root hair curling was also observed in plants inoculated with the clpB-transformed strain, compared to the wild-type strain. The superior root hair curling induction, nodulation ability and symbiotic effectiveness of the clpB-transformed strain may be explained by an increased expression of symbiosis genes. Indeed, higher transcript levels of the nodulation genes nodA and nodC (~3 folds) were detected in the clpB-transformed strain. The improvement of rhizobia by addition of extra-copies of the clpB gene may be a promising strategy to obtain strains with enhanced stress tolerance and symbiotic effectiveness, thus contributing to their success as crop inoculants, particularly under environmental stresses. This is the first report on the successful improvement of a rhizobium with a chaperone gene.
Collapse
Affiliation(s)
- Ana Paço
- ICAAM–Instituto de Ciências Agrárias e Ambientais Mediterrânicas (Laboratório de Microbiologia do Solo), Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002–554, Évora, Portugal
| | - Clarisse Brígido
- ICAAM–Instituto de Ciências Agrárias e Ambientais Mediterrânicas (Laboratório de Microbiologia do Solo), Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002–554, Évora, Portugal
- IIFA–Instituto de Investigação e Formação Avançada, Universidade de Évora, Ap. 94, 7002–554, Évora, Portugal
| | - Ana Alexandre
- ICAAM–Instituto de Ciências Agrárias e Ambientais Mediterrânicas (Laboratório de Microbiologia do Solo), Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002–554, Évora, Portugal
- IIFA–Instituto de Investigação e Formação Avançada, Universidade de Évora, Ap. 94, 7002–554, Évora, Portugal
| | - Pedro F. Mateos
- Departamento de Microbiología y Genética, Centro Hispano Luso de Investigaciones Agrarias, Universidad de Salamanca, 37007, Salamanca, Spain
| | - Solange Oliveira
- ICAAM–Instituto de Ciências Agrárias e Ambientais Mediterrânicas (Laboratório de Microbiologia do Solo), Universidade de Évora, Núcleo da Mitra, Ap. 94, 7002–554, Évora, Portugal
- * E-mail:
| |
Collapse
|
7
|
Lipuma J, Cinege G, Bodogai M, Oláh B, Kiers A, Endre G, Dupont L, Dusha I. AvapBC-type toxin-antitoxin module ofSinorhizobium melilotiinfluences symbiotic efficiency and nodule senescence ofMedicago sativa. Environ Microbiol 2015; 16:3714-29. [DOI: 10.1111/1462-2920.12608] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 08/18/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Justine Lipuma
- Institut Sophia Agrobiotech (ISA); INRA UMR 1355; CNRS UMR 7254; Université de Nice Sophia Antipolis; 400 Route des Chappes - BP167 Sophia Antipolis Cedex F-06903 France
| | - Gyöngyi Cinege
- Institute of Genetics; Biological Research Center; Hungarian Academy of Sciences; P.O. Box 521 Szeged H-6701 Hungary
| | - Monica Bodogai
- Institute of Genetics; Biological Research Center; Hungarian Academy of Sciences; P.O. Box 521 Szeged H-6701 Hungary
| | - Boglárka Oláh
- Institute of Genetics; Biological Research Center; Hungarian Academy of Sciences; P.O. Box 521 Szeged H-6701 Hungary
| | - Aurélie Kiers
- Institut Sophia Agrobiotech (ISA); INRA UMR 1355; CNRS UMR 7254; Université de Nice Sophia Antipolis; 400 Route des Chappes - BP167 Sophia Antipolis Cedex F-06903 France
| | - Gabriella Endre
- Institute of Genetics; Biological Research Center; Hungarian Academy of Sciences; P.O. Box 521 Szeged H-6701 Hungary
| | - Laurence Dupont
- Institut Sophia Agrobiotech (ISA); INRA UMR 1355; CNRS UMR 7254; Université de Nice Sophia Antipolis; 400 Route des Chappes - BP167 Sophia Antipolis Cedex F-06903 France
| | - Ilona Dusha
- Institute of Genetics; Biological Research Center; Hungarian Academy of Sciences; P.O. Box 521 Szeged H-6701 Hungary
| |
Collapse
|
8
|
Abstract
Rhizobia are bacteria in the α-proteobacterial genera Rhizobium, Sinorhizobium, Mesorhizobium, Azorhizobium and Bradyrhizobium that reduce (fix) atmospheric nitrogen in symbiotic association with a compatible host plant. In free-living and/or symbiotically associated rhizobia, amino acids may, in addition to their incorporation into proteins, serve as carbon, nitrogen or sulfur sources, signals of cellular nitrogen status and precursors of important metabolites. Depending on the rhizobia-host plant combination, microsymbiont amino acid metabolism (biosynthesis, transport and/or degradation) is often crucial to the establishment and maintenance of an effective nitrogen-fixing symbiosis and is intimately interconnected with the metabolism of the plant. This review summarizes past findings and current research directions in rhizobial amino acid metabolism and evaluates the genetic, biochemical and genome expression studies from which these are derived. Specific sections deal with the regulation of rhizobial amino acid metabolism, amino acid transport, and finally the symbiotic roles of individual amino acids in different plant-rhizobia combinations.
Collapse
|
9
|
Cell growth inhibition upon deletion of four toxin-antitoxin loci from the megaplasmids of Sinorhizobium meliloti. J Bacteriol 2013; 196:811-24. [PMID: 24317400 DOI: 10.1128/jb.01104-13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Toxin and antitoxin (TA) gene pairs are addiction systems that are present in many microbial genomes. Sinorhizobium meliloti is an N2-fixing bacterial symbiont of alfalfa and other leguminous plants, and its genome consists of three large replicons, a circular chromosome (3.7 Mb) and the megaplasmids pSymA (1.4 Mb) and pSymB (1.7 Mb). S. meliloti carries 211 predicted type II TA genes, each encoding a toxin or an antitoxin. We constructed defined deletion strains that collectively removed the entire pSymA and pSymB megaplasmids except for their oriV regions. Of approximately 100 TA genes on pSymA and pSymB, we identified four whose loss was associated with cell death or stasis unless copies of the genes were supplied in trans. Orthologs of three of these loci have been characterized in other organisms (relB/E [sma0471/sma0473], Fic [DOC] [sma2105], and VapC [PIN] [orf2230/sma2231]), and this report contains the first experimental proof that RES/Xre (smb21127/smb21128) loci can function as a TA system. Transcriptome sequencing (RNA-seq) analysis did not reveal transcriptional differences between the TA systems to account for why deletion of the four "active" systems resulted in cell toxicity. These data suggest that severe cell growth phenotypes result from the loss of a few TA systems and that loss of most TA systems may result in more subtle phenotypes. These four TA systems do not appear to play a direct role in the S. meliloti-alfalfa symbiosis, as strains lacking these TA systems had a symbiotic N2 fixation phenotype that was indistinguishable from the wild type.
Collapse
|
10
|
Ribonucleases in bacterial toxin-antitoxin systems. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:523-31. [PMID: 23454553 DOI: 10.1016/j.bbagrm.2013.02.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 02/05/2013] [Accepted: 02/14/2013] [Indexed: 11/21/2022]
Abstract
Toxin-antitoxin (TA) systems are widespread in bacteria and archaea and play important roles in a diverse range of cellular activities. TA systems have been broadly classified into 5 types and the targets of the toxins are diverse, but the most frequently used cellular target is mRNA. Toxins that target mRNA to inhibit translation can be classified as ribosome-dependent or ribosome-independent RNA interferases. These RNA interferases are sequence-specific endoribonucleases that cleave RNA at specific sequences. Despite limited sequence similarity, ribosome-independent RNA interferases belong to a limited number of structural classes. The MazF structural family includes MazF, Kid, ParE and CcdB toxins. MazF members cleave mRNA at 3-, 5- or 7-base recognition sequences in different bacteria and have been implicated in controlling cell death (programmed) and cell growth, and cellular responses to nutrient starvation, antibiotics, heat and oxidative stress. VapC endoribonucleases belong to the PIN-domain family and inhibit translation by either cleaving tRNA(fMet) in the anticodon stem loop, cleaving mRNA at -AUA(U/A)-hairpin-G- sequences or by sequence-specific RNA binding. VapC has been implicated in controlling bacterial growth in the intracellular environment and in microbial adaptation to nutrient limitation (nitrogen, carbon) and heat shock. ToxN shows structural homology to MazF and is also a sequence-specific endoribonuclease. ToxN confers phage resistance by causing cell death upon phage infection by cleaving cellular and phage RNAs, thereby interfering with bacterial and phage growth. Notwithstanding our recent progress in understanding ribonuclease action and function in TA systems, the environmental triggers that cause release of the toxin from its cognate antitoxin and the precise cellular function of these systems in many bacteria remain to be discovered. This article is part of a Special Issue entitled: RNA Decay mechanisms.
Collapse
|
11
|
Brígido C, Robledo M, Menéndez E, Mateos PF, Oliveira S. A ClpB chaperone knockout mutant of Mesorhizobium ciceri shows a delay in the root nodulation of chickpea plants. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:1594-1604. [PMID: 23134119 DOI: 10.1094/mpmi-05-12-0140-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Several molecular chaperones are known to be involved in bacteria stress response. To investigate the role of chaperone ClpB in rhizobia stress tolerance as well as in the rhizobia-plant symbiosis process, the clpB gene from a chickpea microsymbiont, strain Mesorhizobium ciceri LMS-1, was identified and a knockout mutant was obtained. The ClpB knockout mutant was tested to several abiotic stresses, showing that it was unable to grow after a heat shock and it was more sensitive to acid shock than the wild-type strain. A plant-growth assay performed to evaluate the symbiotic performance of the clpB mutant showed a higher proportion of ineffective root nodules obtained with the mutant than with the wild-type strain. Nodulation kinetics analysis showed a 6- to 8-day delay in nodule appearance in plants inoculated with the ΔclpB mutant. Analysis of nodC gene expression showed lower levels of transcript in the ΔclpB mutant strain. Analysis of histological sections of nodules formed by the clpB mutant showed that most of the nodules presented a low number of bacteroids. No differences in the root infection abilities of green fluorescent protein-tagged clpB mutant and wild-type strains were detected. To our knowledge, this is the first study that presents evidence of the involvement of the chaperone ClpB from rhizobia in the symbiotic nodulation process.
Collapse
|
12
|
Arcus VL, McKenzie JL, Robson J, Cook GM. The PIN-domain ribonucleases and the prokaryotic VapBC toxin-antitoxin array. Protein Eng Des Sel 2010; 24:33-40. [PMID: 21036780 DOI: 10.1093/protein/gzq081] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The PIN-domains are small proteins of ~130 amino acids that are found in bacteria, archaea and eukaryotes and are defined by a group of three strictly conserved acidic amino acids. The conserved three-dimensional structures of the PIN-domains cluster these acidic residues in an enzymatic active site. PIN-domains cleave single-stranded RNA in a sequence-specific, Mg²+- or Mn²+-dependent manner. These ribonucleases are toxic to the cells which express them and to offset this toxicity, they are co-expressed with tight binding protein inhibitors. The genes encoding these two proteins are adjacent in the genome of all prokaryotic organisms where they are found. This sequential arrangement of inhibitor-RNAse genes conforms to that of the so-called toxin-antitoxin (TA) modules and the PIN-domain TAs have been named VapBC TAs (virulence associated proteins, VapB is the inhibitor which contains a transcription factor domain and VapC is the PIN-domain ribonuclease). The presence of large numbers of vapBC loci in disparate prokaryotes has motivated many researchers to investigate their biochemical and biological functions. For example, the devastating human pathogen Mycobacterium tuberculosis has 45 vapBC loci encoded in its genome whereas its non-pathogenic relative, Mycobacterium smegmatis has just one vapBC operon. On another branch of the prokaryotic tree, the nitrogen-fixing symbiont of legumes, Sinorhizobium meliloti has 21 vapBC loci and at least one of these loci have been implicated in the regulation of growth in the plant nodule. A range of biological functions has been suggested for these operons and this review sets out to survey the PIN-domains and summarise the current knowledge about the vapBC TA systems and their roles in diverse bacteria.
Collapse
Affiliation(s)
- Vickery L Arcus
- Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
| | | | | | | |
Collapse
|
13
|
Miclea PS, Péter M, Végh G, Cinege G, Kiss E, Váró G, Horváth I, Dusha I. Atypical transcriptional regulation and role of a new toxin-antitoxin-like module and its effect on the lipid composition of Bradyrhizobium japonicum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:638-650. [PMID: 20367472 DOI: 10.1094/mpmi-23-5-0638] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A toxin-antitoxin (TA)-like system (designated as bat/bto genes) was identified in Bradyrhizobium japonicum, based on sequence homology and similarities in organization and size to known TA systems. Deletion of the bat/bto module resulted in pleiotropic alterations in cell morphology and metabolism. The generation time of the mutant was considerably decreased in rich media. Atomic force microscopy revealed the modified shape (shorter and wider) and softness of mutant cells. The synthesis of phosphatidylcholine was completely blocked in the mutant bacteria, and vaccenic acid, the predominant fatty acid of membranes of the wild-type cell, was replaced by palmitic acid in the mutant membranes. The mutant bacteria synthesized incomplete lipopolysaccharide molecules. Remarkable changes in the membrane lipid composition may explain the observed morphological alterations and growth properties of the mutant bacteria. The overlapping promoter region of bat/bto and glpD (coding for the aerobic sn-glycerol-3-phosphate dehydrogenase) genes suggests a complex regulation and the involvement of bat/bto in the control of main metabolic pathways and an important role in the maintenance of a normal physiological state of B. japonicum. These data reveal new aspects of the role of TA systems in bacteria.
Collapse
Affiliation(s)
- Paul S Miclea
- Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Hayes CS, Low DA. Signals of growth regulation in bacteria. Curr Opin Microbiol 2009; 12:667-73. [PMID: 19854099 DOI: 10.1016/j.mib.2009.09.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 08/15/2009] [Accepted: 09/20/2009] [Indexed: 10/20/2022]
Abstract
A fundamental characteristic of cells is their ability to regulate growth in response to changing environmental conditions. This review focuses on recent progress toward understanding the mechanisms by which bacterial growth is regulated. These phenomena include the 'viable but not culturable' (VBNC) state, in which bacterial growth becomes conditional, and 'persistence', which confers antibiotic resistance to a small fraction of bacteria in a population. Notably, at least one form of persistence appears to involve the generation of nongrowing phenotypic variants after transition through stationary phase. The possible roles of toxin-antitoxin modules in growth control are explored, as well as other mechanisms including contact-dependent growth inhibition, which regulates cellular metabolism and growth through binding to an outer membrane protein receptor.
Collapse
Affiliation(s)
- Christopher S Hayes
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
| | | |
Collapse
|
15
|
Chang WS, Franck WL, Cytryn E, Jeong S, Joshi T, Emerich DW, Sadowsky MJ, Xu D, Stacey G. An oligonucleotide microarray resource for transcriptional profiling of Bradyrhizobium japonicum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:1298-307. [PMID: 17918631 DOI: 10.1094/mpmi-20-10-1298] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A DNA microarray, comprising 70-mer oligonucleotides, representing 8,453 open reading frames (ORFs), was constructed based on the Bradyrhizobium japonicum strain USDA110 genomic sequence. New annotation predicted 199 additional genes, which were added to the microarray and were shown to be transcribed. These arrays were used to profile transcription in cells under a variety of conditions, including growth in minimal versus rich medium, osmotic stress, and free-living cells versus bacteroids. Increased expression was seen for genes involved in translation, motility, and cell envelope synthesis in rich medium whereas expression increased in minimal medium for genes involved in vitamin biosynthesis and stress responses. Treatment with 50 mM NaCl activated stress-inducible genes but repressed genes involved in chemotaxis and motility. Strikingly, no known transport systems for accumulation of compatible solutes or osmoprotectants were induced in response to osmotic stress. A number of nif, fix, and hup genes, but not all, were upregulated in bacteroids. The B. japonicum type III secretion system, known to be important in early nodulation, was downregulated in bacteroids. The availability of a reliable, low-cost B. japonicum microarray provides a useful tool for functional genomic studies of one of the most agriculturally important bacteria.
Collapse
Affiliation(s)
- Woo-Suk Chang
- National Center for Soybean Biotechnology, University of Missouri, Columbia 65211, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Bobik C, Meilhoc E, Batut J. FixJ: a major regulator of the oxygen limitation response and late symbiotic functions of Sinorhizobium meliloti. J Bacteriol 2006; 188:4890-902. [PMID: 16788198 PMCID: PMC1482993 DOI: 10.1128/jb.00251-06] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sinorhizobium meliloti exists either in a free-living state in the soil or in symbiosis within legume nodules, where the bacteria differentiate into nitrogen-fixing bacteroids. Expression of genes involved in nitrogen fixation and associated respiration is governed by two intermediate regulators, NifA and FixK, respectively, which are controlled by a two-component regulatory system FixLJ in response to low-oxygen conditions. In order to identify the FixLJ regulon, gene expression profiles were determined in microaerobic free-living cells as well as during the symbiotic life of the bacterium for the wild type and a fixJ null-mutant strain. We identified 122 genes activated by FixJ in either state, including 87 novel targets. FixJ controls 74% of the genes induced in microaerobiosis (2% oxygen) and the majority of genes expressed in mature bacteroids. Ninety-seven percent of FixJ-activated genes are located on the symbiotic plasmid pSymA. Transcriptome profiles of a nifA and a fixK mutant showed that NifA activates a limited number of genes, all specific to the symbiotic state, whereas FixK controls more than 90 genes, involved in free-living and/or symbiotic life. This study also revealed that FixJ has no other direct targets besides those already known. FixJ is involved in the regulation of functions such as denitrification or amino acid/polyamine metabolism and transport. Mutations in selected novel FixJ targets did not affect the ability of the bacteria to form nitrogen-fixing nodules on Medicago sativa roots. From these results, we propose an updated model of the FixJ regulon.
Collapse
Affiliation(s)
- Christine Bobik
- Laboratoire des Interactions Plantes Microorganismes (LIPM), UMR441-2594 CNRS/INRA BP52627, Chemin de Borde Rouge, Auzeville, 31326 Castanet-Tolosan Cedex, France
| | | | | |
Collapse
|
17
|
Bodogai M, Ferenczi S, Bashtovyy D, Miclea P, Papp P, Dusha I. The ntrPR operon of Sinorhizobium meliloti is organized and functions as a toxin-antitoxin module. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:811-22. [PMID: 16838793 DOI: 10.1094/mpmi-19-0811] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The chromosomal ntrPR operon of Sinorhizobium meliloti encodes a protein pair that forms a toxin-antitoxin (TA) module, the first characterized functional TA system in Rhizobiaceae. Similarly to other bacterial TA systems, the toxin gene ntrR is preceded by and partially overlaps with the antitoxin gene ntrP. Based on protein homologies, the ntrPR operon belongs to the vapBC family of TA systems. The operon is negatively autoregulated by the NtrPNtrR complex. Promoter binding by NtrP is weak; stable complex formation also requires the presence of NtrR. The N-terminal part of NtrP is responsible for the interaction with promoter DNA, whereas the C-terminal part is required for protein-protein interactions. In the promoter region, a direct repeat sequence was identified as the binding site of the NtrPNtrR complex. NtrR expression resulted in the inhibition of cell growth and colony formation; this effect was counteracted by the presence of the antitoxin NtrP. These results and our earlier observations demonstrating a less effective downregulation of a wide range of symbiotic and metabolic functions in the ntrR mutant under microoxic conditions and an increased symbiotic efficiency with the host plant alfalfa suggest that the ntrPR module contributes to adjusting metabolic levels under symbiosis and other stressful conditions.
Collapse
Affiliation(s)
- Monica Bodogai
- Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged
| | | | | | | | | | | |
Collapse
|
18
|
Capela D, Filipe C, Bobik C, Batut J, Bruand C. Sinorhizobium meliloti differentiation during symbiosis with alfalfa: a transcriptomic dissection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:363-72. [PMID: 16610739 DOI: 10.1094/mpmi-19-0363] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Sinorhizobium meliloti is a soil bacterium able to induce the formation of nodules on the root of specific legumes, including alfalfa (Medicago sativa). Bacteria colonize nodules through infection threads, invade the plant intracellularly, and ultimately differentiate into bacteroids capable of reducing atmospheric nitrogen to ammonia, which is directly assimilated by the plant. As a first step to describe global changes in gene expression of S. meliloti during the symbiotic process, we used whole genome microarrays to establish the transcriptome profile of bacteria from nodules induced by a bacterial mutant blocked at the infection stage and from wild-type nodules harvested at various timepoints after inoculation. Comparison of these profiles to those of cultured bacteria grown either to log or stationary phase as well as examination of a number of genes with known symbiotic transcription patterns allowed us to correlate global gene-expression patterns to three known steps of symbiotic bacteria bacteroid differentiation, i.e., invading bacteria inside infection threads, young differentiating bacteroids, and fully differentiated, nitrogen-fixing bacteroids. Finally, analysis of individual gene transcription profiles revealed a number of new potential symbiotic genes.
Collapse
Affiliation(s)
- Delphine Capela
- Laboratoire des Interactions Plantes-Microorganismes, UMR INRA-CNRS 441-2594, BP52627, 31326 Castanet-Tolosan, France
| | | | | | | | | |
Collapse
|
19
|
Letoha T, Somlai C, Takács T, Szabolcs A, Rakonczay Z, Jármay K, Szalontai T, Varga I, Kaszaki J, Boros I, Duda E, Hackler L, Kurucz I, Penke B. The proteasome inhibitor MG132 protects against acute pancreatitis. Free Radic Biol Med 2005; 39:1142-51. [PMID: 16214030 DOI: 10.1016/j.freeradbiomed.2005.06.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 06/07/2005] [Accepted: 06/09/2005] [Indexed: 02/06/2023]
Abstract
The cell-permeant MG132 tripeptide (Z-Leu-Leu-Leu-aldehyde) is a peptide aldehyde proteasome inhibitor that also inhibits other proteases, including calpains and cathepsins. By blocking the proteasome, this tripeptide has been shown to induce the expression of cell-protective heat shock proteins (HSPs) in vitro. Effects of MG132 were studied in an in vivo model of acute pancreatitis. Pancreatitis was induced in male Wistar rats by injecting 2 x 100 microug/kg cholecystokinin octapeptide intraperitoneally (ip) at an interval of 1 h. Pretreating the animals with 10 mg/kg MG132 ip before the induction of pancreatitis significantly inhibited IkappaB degradation and subsequent activation of nuclear factor-kappaB (NF-kappaB). MG132 also increased HSP72 expression. Induction of HSP72 and inhibition of NF-kappaB improved parameters of acute pancreatitis. Thus MG132 significantly decreased serum amylase, pancreatic weight/body weight ratio, pancreatic myeloperoxidase activity, proinflammatory cytokine concentrations, and the expression of pancreatitis-associated protein. Parameters of oxidative stress (GSH, MDA, SOD, etc.) were improved in both the serum and the pancreas. Histopathological examinations revealed that pancreatic specimens of animals pretreated with the peptide demonstrated milder edema, cellular damage, and inflammatory activity. Our findings show that simultaneous inhibition of calpains, cathepsins, and the proteasome with MG132 prevents the onset of acute pancreatitis.
Collapse
Affiliation(s)
- Tamás Letoha
- Department of Medical Chemistry, University of Szeged, Dóm tér 8, H-6720 Szeged, Hungary.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Bobay BG, Andreeva A, Mueller GA, Cavanagh J, Murzin AG. Revised structure of the AbrB N-terminal domain unifies a diverse superfamily of putative DNA-binding proteins. FEBS Lett 2005; 579:5669-74. [PMID: 16223496 DOI: 10.1016/j.febslet.2005.09.045] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 09/14/2005] [Accepted: 09/19/2005] [Indexed: 10/25/2022]
Abstract
New relationships found in the process of updating the structural classification of proteins (SCOP) database resulted in the revision of the structure of the N-terminal, DNA-binding domain of the transition state regulator AbrB. The dimeric AbrB domain shares a common fold with the addiction antidote MazE and the subunit of uncharacterized protein MraZ implicated in cell division and cell envelope formation. It has a detectable sequence similarity to both MazE and MraZ thus providing an evolutionary link between the two proteins. The putative DNA-binding site of AbrB is found on the same face as the DNA-binding site of MazE and appears similar, both in structure and sequence, to the exposed conserved region of MraZ. This strongly suggests that MraZ also binds DNA and allows for a consensus model of DNA recognition by the members of this novel protein superfamily.
Collapse
Affiliation(s)
- Benjamin G Bobay
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, 27695, USA
| | | | | | | | | |
Collapse
|
21
|
Rodríguez-Quiñones F, Maguire M, Wallington EJ, Gould PS, Yerko V, Downie JA, Lund PA. Two of the three groEL homologues in Rhizobium leguminosarum are dispensable for normal growth. Arch Microbiol 2005; 183:253-65. [PMID: 15830189 DOI: 10.1007/s00203-005-0768-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2004] [Revised: 02/10/2005] [Accepted: 02/24/2005] [Indexed: 01/16/2023]
Abstract
Although many bacteria contain only a single groE operon encoding the essential chaperones GroES and GroEL, examples of bacteria containing more than one groE operon are common. The root-nodulating bacterium Rhizobium leguminosarum contains at least three operons encoding homologues to Escherichia coli GroEL, referred to as Cpn60.1, Cpn60.2 and Cpn60.3, respectively. We report here a detailed analysis of the requirement for and relative levels of these three proteins. Cpn60.1 is present at higher levels than Cpn60.2, and Cpn60.3 protein could not be detected under any conditions although the cpn60.3 gene is transcribed under anaerobic conditions. Insertion mutations could not be constructed in cpn60.1 unless a complementing copy was present, showing that this gene is essential for growth under the conditions used here. Both cpn60.2 and cpn60.3 could be inactivated with no loss of viability, and a double cpn60.2 cpn60.3 mutant was also constructed which was fully viable. Thus only Cpn60.1 is required for growth of this organism.
Collapse
|