Project description:Rhizobia are soil bacteria that induce nodule formation on leguminous plants. In the nodules, they reduce dinitrogen to ammonium that can be utilized by plants. Besides nitrogen fixation, rhizobia have other symbiotic functions in plants including phosphorus and iron mobilization and protection of the plants against various abiotic stresses including salinity. Worldwide, about 20% of cultivable and 33% of irrigation land is saline, and it is estimated that around 50% of the arable land will be saline by 2050. Salinity inhibits plant growth and development, results in senescence, and ultimately plant death. The purpose of this study was to investigate how rhizobia, isolated from Kenyan soils, relieve common beans from salinity stress. The yield loss of common bean plants, which were either not inoculated or inoculated with the commercial R. tropici rhizobia CIAT899 was reduced by 73% when the plants were exposed to 300 mM NaCl, while only 60% yield loss was observed after inoculation with a novel indigenous isolate from Kenyan soil, named S3. Expression profiles showed that genes involved in the transport of mineral ions (such as K+, Ca2+, Fe3+, PO43-, and NO3-) to the host plant, and for the synthesis and transport of osmotolerance molecules (soluble carbohydrates, amino acids, and nucleotides) are highly expressed in S3 bacteroids during salt stress than in the controls. Furthermore, genes for the synthesis and transport of glutathione and γ-aminobutyric acid were upregulated in salt-stressed and S3-inocculated common bean plants. We conclude that microbial osmolytes, mineral ions, and antioxidant molecules from rhizobia enhance salt tolerance in common beans.
2022-10-31 | GSE216374 | GEO
Project description:Genomes of rhizobia isolated from common bean nodules
Project description:Legume plants can establish symbiotic nitrogen fixation (SNF) with rhizobia mostly in root nodules, where rhizobia-infected cells are accompanied with uninfected cells in a mosaic pattern. Inside the mature nodules of legume, carbon and nitrogen nutrients between host plant cells and their resident bacteria are actively exchanged. To elucidate the metabolite dynamics relevant for SNF in nodules, three cell-types from nodule tissues of a model legume, Lotus japonicus, were isolated using laser microdissesction, and transcriptome analysis was done by an oligoarray with 60-mer length representing 21,495 genes. In our cell-type-specific profiling, many genes were identified as being expressed in nodules with spatial-specific manners. Among them, genes coding for metabolic enzymes were classified according to their function, and detailed data analysis figured out that secondary metabolic pathway was highly activated in nodule cortex. In particular, a number of metabolic genes for phenyl propanoid pathway were found as highly expressed genes accompanied with those encoding putative transporters of secondary metabolites. These data suggest the involvement of novel physiological function of phenylpropanoids in SNF.
Project description:Legume plants can establish symbiotic nitrogen fixation (SNF) with rhizobia mostly in root nodules, where rhizobia-infected cells are accompanied with uninfected cells in a mosaic pattern. Inside the mature nodules of legume, carbon and nitrogen nutrients between host plant cells and their resident bacteria are actively exchanged. To elucidate the metabolite dynamics relevant for SNF in nodules, three cell-types from nodule tissues of a model legume, Lotus japonicus, were isolated using laser microdissesction, and transcriptome analysis was done by an oligoarray with 60-mer length representing 21,495 genes. In our cell-type-specific profiling, many genes were identified as being expressed in nodules with spatial-specific manners. Among them, genes coding for metabolic enzymes were classified according to their function, and detailed data analysis figured out that secondary metabolic pathway was highly activated in nodule cortex. In particular, a number of metabolic genes for phenyl propanoid pathway were found as highly expressed genes accompanied with those encoding putative transporters of secondary metabolites. These data suggest the involvement of novel physiological function of phenylpropanoids in SNF. Gene expression in three different cell-types of Lotus japonicus nodule was measured. Three independent experiments were performed at each cell-types.
Project description:Legumes establish symbiosis with soil rhizobia forming root nodules that fix atmospheric nitrogen. The central role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in nodule biology has been clearly established. Recently, hydrogen sulfide (H2S) and other reactive sulfur species (RSS) have emerged as novel signaling molecules in animals and plants. A major mechanism by which ROS, RNS, and RSS fulfil their signaling role is the post-translational modification of proteins. To identify possible functions of H2S in nodule development and senescence, we used the tag-switch method to analyze quantitative changes in the persulfidation profile of common bean (Phaseolus vulgaris) nodules at different developmental stages. The proteomic analysis suggests that persulfidation plays a major regulatory role in plant and bacteroid metabolism and senescence. In addition, the effect of a H2S donor on several proteins involved in ROS and RNS homeostasis was investigated. The results obtained using nodule extracts and recombinant proteins suggest a crosstalk between H2S, ROS, and RNS, and a protective function of persulfidation on redox-sensitive enzymes from oxidative modifications that may cause enzyme inactivation. It is concluded that the general decrease of persulfidation levels observed in plant proteins of aging nodules is one of the mechanisms that cause the disruption of redox homeostasis leading to senescence.
Project description:12plex_medicago_2013-08 - r108 in symbiosis with rhizobia wt or rhizobia mutant for baca. - Two experiments to compare the transcriptomic response of medicago plants: Agar medium versus Phytagel medium (exp1) and rhizobium WT versus BacA (exp2). - Medicago truncatula ecotype R108 was inoculated with the symbiotic rhizobium Sinorhizobium meliloti strain Sm1021 and with its derivative mutant delta bacA. Nodules were collected 13 days after inoculation, and RNA were prepared for transcriptome analysis, there were three biological independant experiements.
Project description:Some legume plants can establish a nitrogen-fixing symbiosis with rhizobia. Compatibilty between rhizobia and legumes is determined at species-specific level, but there are variations on the efficiency of the process determined by the capacity of the plant to select specific strains that are better partners in terms of the biological outcome. In this work we used a model system based in the coevolution of two genetic pools of common bean (Phaseolus vulgaris) with strains of R. etli that establish a more efficient interaction to study the transcriptional changes occurring in roots at an early time of the interaction.