title: Metabolomic Profiling of Bradyrhizobium diazoefficiens-Induced Root Nodules Reveals Both Host Plant-Specific and Developmental Signatures.
abstract: Bradyrhizobium diazoefficiens is a nitrogen-fixing endosymbiont, which can grow inside root-nodule cells of the agriculturally important soybean and other host plants. Our previous studies described B. diazoefficiens host-specific global expression changes occurring during legume infection at the transcript and protein level. In order to further characterize nodule metabolism, we here determine by flow injection-time-of-flight mass spectrometry analysis the metabolome of (i) nodules and roots from four different B. diazoefficiens host plants; (ii) soybean nodules harvested at different time points during nodule development; and (iii) soybean nodules infected by two strains mutated in key genes for nitrogen fixation, respectively. Ribose (soybean), tartaric acid (mungbean), hydroxybutanoyloxybutanoate (siratro) and catechol (cowpea) were among the metabolites found to be specifically elevated in one of the respective host plants. While the level of C4-dicarboxylic acids decreased during soybean nodule development, we observed an accumulation of trehalose-phosphate at 21 days post infection (dpi). Moreover, nodules from non-nitrogen-fixing bacteroids (nifA and nifH mutants) showed specific metabolic alterations; these were also supported by independent transcriptomics data. The alterations included signs of nitrogen limitation in both mutants, and an increased level of a phytoalexin in nodules induced by the nifA mutant, suggesting that the tissue of these nodules exhibits defense and stress reactions.
authors.affiliation: Department of Plant and Microbial Biology, University of Z&#252;rich, CH-8057 Z&#252;rich, Switzerland. marti.lardi@access.uzh.ch.
authors.forename: Martina
authors.initials: M
authors.lastname: Lardi
authors.affiliation: Institute of Microbiology, Eidgen&#246;ssische Technische Hochschule (ETH) Z&#252;rich, CH-8093 Z&#252;rich, Switzerland. vmurset@hotmail.com.
authors.forename: Valérie
authors.initials: V
authors.lastname: Murset
authors.affiliation: Institute of Microbiology, Eidgen&#246;ssische Technische Hochschule (ETH) Z&#252;rich, CH-8093 Z&#252;rich, Switzerland. fischeha@ethz.ch.
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Fischer
authors.affiliation: Department of Soil Microbiology and Symbiotic Systems, Estaci&#243;n Experimental del Zaid&#237;n, Consejo Superior de Investigaciones Cient&#237;ficas (CSIC), E-18080 Granada, Spain. socorro.mesa@eez.csic.es.
authors.forename: Socorro
authors.initials: S
authors.lastname: Mesa
authors.affiliation: Agroscope, Institute for Plant Production Sciences, Research Group Molecular Diagnostics, Genomics and Bioinformatics &amp; Swiss Institute of Bioinformatics (SIB), CH-8820 W&#228;denswil, Switzerland. christian.ahrens@agroscope.admin.ch.
authors.forename: Christian H
authors.initials: CH
authors.lastname: Ahrens
authors.affiliation: Institute of Molecular Systems Biology, ETH Z&#252;rich, CH-8093 Z&#252;rich, Switzerland. zamboni@imsb.biol.ethz.ch.
authors.forename: Nicola
authors.initials: N
authors.lastname: Zamboni
authors.affiliation: Department of Plant and Microbial Biology, University of Z&#252;rich, CH-8057 Z&#252;rich, Switzerland. gabriella.pessi@uzh.ch.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Pessi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D020369:Bradyrhizobium / Q000235:genetics* / Q000472:pathogenicity; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D013058:Mass Spectrometry; D055432:Metabolomics / Q000379:methods*; D009154:Mutation; D009586:Nitrogen Fixation; D025341:Principal Component Analysis; D053204:Root Nodules, Plant / Q000737:chemistry / Q000254:growth & development* / Q000382:microbiology; D013025:Glycine max / Q000737:chemistry / Q000254:growth & development / Q000382:microbiology*; D013559:Symbiosis; D000070658:Vigna / Q000737:chemistry / Q000254:growth & development / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins
keywords: host-specific nodule metabolism; metabolomics; nifA; nifH transcriptomics; nodule development; rhizobia; symbiosis