INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Genetics and metabolomics analysis of a non-efficient Medicago-rhizobia symbiosis
TORRES TEJERIZO G.A.; NILSSON J.F.; LAGARES A.; NIEHAUS K.; WIBBERG D.; PISTORIO M.; PÜHLER A.; BEDNARZ H.; CASTELLANI L.G.; SCHLÜTER A.
Conferencia; 12th European Nitrogen Fixation Conference; 2016
Alfalfa (Medicago sativa) is the most widely cultivated forage legume for cattle and animal feeding, occupying about 32 million hectares over the world. Therefore, management of the N2-fixing symbiosis is important to maximize the production of this crop. Symbiosis is a very complex process and, particularly, the Medicago-rhizobia symbiosis is highly specific. Ensifer meliloti is the model of efficient rhizobia able to infect Medicago that, after several steps, form nodules where they differentiate into bacteroids. These bacteroids are responsible for a successful nitrogen-fixing stage. Nevertheless, not only Ensifer strains are able to nodulate Medicago; Oregon-like strains are also able to infect alfalfa. Oregon-like rhizobia (e.g. LPU83) are acid tolerant, very competitive for the nodulation of alfalfa in acids soils, but inefficient for biological nitrogen fixation. The nodules developed by LPU83 harbored only few bacteroids compared to those of plants infected by the reference strain E. meliloti 2011 and the senescence zone develops early. This large senescence zone allows a short nitrogen fixation zone (Wegener et al., 2001). Previously, we have presented a draft genome of LPU83 (Wibberg et al., 2014). In order to elucidate the deficient phenotype of LPU83, genome analyses and metabolomics were performed. Also in a previous work, we study nodulations factors and nod gene cluster (Torres Tejerizo et al., 2011). Now, we evaluated others genes also involved in the synthesis of symbiosis determinants. Comparison of exopolysaccharide synthesis gene cluster show that while in E. meliloti 2011 only one gene cluster is found, two clusters were found in LPU83, one in the chromosome and one in plasmid pLPU83a. Some of the genes were duplicated or not present in the clusters, but elsewhere in the genome. Deletion of the exo cluster of the plasmid did not modify the nodules development. Lipopolysaccharide synthesis gene cluster were also compared and the organization among E. meliloti and LPU83 was found more similar than with Rhizobium etli or Rhizobium leguminosarum. Moreover, the genes for nitrogen metabolism enzymes were present in LPU83. Metabolomics analyses of the full nodules of E. meliloti 2011 and LPU83 were performed. Striking differences in metabolite profiles were obtained, among them dicarboxylic acids and sugar compounds.Accordingly, Oregon-like rhizobia could be used as key reference strains to perform comparatives studies aiming to detect and identify genes that could be involved in an efficient or inefficient symbiosis.Torres Tejerizo, G., et al. 2011. J Bacteriol, 193, 30-39.Wegener, C., et al. 2001. Symbiosis, 30, 141-162.Wibberg, D., et al. 2014. J Biotechnol, 176, 40-1.