Project description:Expression data from B. japonicum soybean root nodules including a nodulation time-course experiment with soybean nodules harvested at 10, 13, 21 and 31 dpi and transcriptome of bacteroids formed by a mutant defective in the RNA polymerase transcription factor sigma 54. Two reference data sets were established using B. japonicum cells grown in PSY medium under either aerobic or micro-aerobic conditions. Keywords: genetic modification, time course, growth conditions
Project description:part of GSE8478: Genome-wide transcript analysis of Bradyrhizobium japonicum bacteroids in soybean root nodules This SuperSeries is composed of the SubSeries listed below.
Project description:Legumes perform symbiotic nitrogen fixation through rhizobial bacteroids housed in specialised root nodules. The biochemical process is energy‐intensive and consumes a huge carbon source to generate sufficient reducing power. To maintain the symbiosis, malate is supplied by legume nodules to bacteroids as their major carbon and energy source in return for ammonium ions and nitrogenous compounds. To sustain the carbon supply to bacteroids, nodule cells undergo drastic reorganisation of carbon metabolism. Here, a comprehensive quantitative comparison of the mitochondrial proteomes between root nodules and uninoculated roots was performed using data‐independent acquisition proteomics, revealing the modulations in nodule mitochondrial proteins and pathways in response to carbon reallocation. Corroborated our findings with that from the literature, we believe nodules preferably allocate cytosolic phosphoenolpyruvates towards malate synthesis in lieu of pyruvate synthesis, and nodule mitochondria prefer malate over pyruvate as the primary source of NADH for ATP production. Moreover, the differential regulation of respiratory chain‐associated proteins suggests that nodule mitochondria could enhance the efficiencies of complexes I and IV for ATP synthesis. This study highlighted a quantitative proteomic view of the mitochondrial adaptation in soybean nodules.
Project description:Certain alpha- and beta-proteobacteria, the rhizobia, are able to infect legume roots, elicit root nodules, and live therein as endosymbiotic, nitrogen-fixing bacteroids. Host recognition and specificity are the results of consecutive programming events in bacteria and host plants in which important signaling molecules, e.g. plant flavonoids and rhizobial lipooligosaccharides, play key roles. Here, we introduce a new aspect of this symbiosis: the adaptive response to hosts. In contrast to host specificity, which determines early steps in bacteria-plant interaction, the adaptation to hosts refers to late events in mature bacteroids where specific genes are transcribed and translated that help the endosymbionts to meet the disparate environmental requirements imposed by the hosts in which they live. This concept was elaborated with Bradyrhizobium japonicum and three different legumes (soybean, cowpea, siratro). We systematically analyzed and compared the transcriptomes as well as the proteomes in bacteroids from root nodules of the three hosts. Transcripts and proteins were thus identified which are induced in only one of the three hosts. We then focused on those determinants that were congruent in the two data sets of host-specific transcripts and proteins, and arrived at 20 for soybean, 7 for siratro, and 4 for cowpea. One conspicuous gene cluster for a predicted ABC-type transporter, differentially expressed in siratro, was deleted. The corresponding mutant had a symbiotic defect on siratro rather than on soybean or cowpea. This result demonstrates the value of the applied approach and corroborates the host-specific adaptation concept. B. japonicum transcriptome was determined for the three different host plants
Project description:Metabolomics and transcriptomics of Bradyrhizobium diazoefficiens-induced root nodules 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 transcriptomics data that was generated for the two mutant strains and were helpful to separate for some examples the respective bacterial and plant contributions to the metabolic profile. 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.
Project description:Background: During the symbiosis with legumes, Bradyrhizobium japonicum cells infect roots where they induce the formation of root nodules and differentiate into intracellular nitrogen-fixing bacteroids. We used differential RNA-seq (dRNA-seq) for the genome-wide detection of transcriptional start sites (TSSs) in B. japonicum USDA 110 cells grown free-living or as bacteroids in soybean root nodules. Results: A newly developed TSS recognition procedure based on machine learning allowed us to map 15,923 TSSs: 14,360 in free-living bacteria, 4,329 in bacteroids and 2,766 in both living conditions. Using a proteogenomics approach, we provide evidence for the translation of 107 new transcripts including 14 with TSSs in annotated genes. In addition, we provide evidence for 178 shorter or longer proteins, 109 of them with TSS support. Based on our TSS map and a new de novo promoter prediction algorithm, we identified promoter motifs mainly used in nodules (similar to RpoN-dependent promoters) or under both conditions (similar to RpoD-dependent promoters). The data is made available in a generic feature format (GFF) file along with an updated and extended genome annotation comprising promoters, TSSs and terminators. The value of such a TSS and promoter map beyond the identification of novel transcripts and ORFs is illustrated by the experimental analysis of an antisense RNA, which is a by-product of transcriptional interference in a gene encoding a cytochrome P450 highly expressed in nodules. Conclusions: The genome-wide TSS and promoter map along with the extended genome annotation represents a very useful resource for detailed analyses of gene regulation and further systems biology studies on B. japonicum in symbiosis with soybean.
Project description:Certain alpha- and beta-proteobacteria, the rhizobia, are able to infect legume roots, elicit root nodules, and live therein as endosymbiotic, nitrogen-fixing bacteroids. Host recognition and specificity are the results of consecutive programming events in bacteria and host plants in which important signaling molecules, e.g. plant flavonoids and rhizobial lipooligosaccharides, play key roles. Here, we introduce a new aspect of this symbiosis: the adaptive response to hosts. In contrast to host specificity, which determines early steps in bacteria-plant interaction, the adaptation to hosts refers to late events in mature bacteroids where specific genes are transcribed and translated that help the endosymbionts to meet the disparate environmental requirements imposed by the hosts in which they live. This concept was elaborated with Bradyrhizobium japonicum and three different legumes (soybean, cowpea, siratro). We systematically analyzed and compared the transcriptomes as well as the proteomes in bacteroids from root nodules of the three hosts. Transcripts and proteins were thus identified which are induced in only one of the three hosts. We then focused on those determinants that were congruent in the two data sets of host-specific transcripts and proteins, and arrived at 20 for soybean, 7 for siratro, and 4 for cowpea. One conspicuous gene cluster for a predicted ABC-type transporter, differentially expressed in siratro, was deleted. The corresponding mutant had a symbiotic defect on siratro rather than on soybean or cowpea. This result demonstrates the value of the applied approach and corroborates the host-specific adaptation concept.
Project description:Legume plants can form root organs called nodules where they house intracellular symbiotic rhizobium bacteria. Within nodule cells, rhizobia differentiate into bacteroids, which fix nitrogen for the benefit of the plant. Depending on the combination of host plants and rhizobial strains, the output of rhizobium-legume interactions is varying from non-fixing associations to symbioses that are highly beneficial for the plant. Bradyrhizobium diazoefficiens USDA110 was isolated as a soybean symbiont but it can also establish a functional symbiotic interaction with Aeschynomene afraspera. In contrast to soybean, A. afraspera triggers terminal bacteroid differentiation, a process involving bacterial cell elongation, polyploidy and membrane permeability leading to loss of bacterial viability while plants increase their symbiotic benefit. A combination of plant metabolomics, bacterial proteomics and transcriptomics along with cytological analyses was used to study the physiology of USDA110 bacteroids in these two host plants. We show that USDA110 establish a poorly efficient symbiosis with A. afraspera, despite the full activation of the bacterial symbiotic program. We found molecular signatures of high level of stress in A. afraspera bacteroids whereas those of terminal bacteroid differentiation were only partially activated. Finally, we show that in A. afraspera, USDA110 bacteroids undergo an atypical terminal differentiation hallmarked by the disconnection of the canonical features of this process. This study pinpoints how a rhizobium strain can adapt its physiology to a new host and cope with terminal differentiation when it did not co-evolve with such a host.
Project description:Rhizobia are soil bacteria that can enter into complex symbiotic relationships with legumes, where rhizobia induce the formation of nodules on the plant root. Inside nodules, rhizobia differentiate into nitrogen-fixing bacteroids that reduce atmospheric nitrogen into ammonia, secreting it to the plant host in exchange for carbon. During the transition from free-living bacteria to bacteroids, rhizobial metabolism undergoes major changes. To investigate the metabolism of bacteroids and contrast it with the free-living state, we quantified the proteome of unlabelled bacteroids relative to 15N-labelled free-living rhizobia. The data were used to build a core metabolic model of pea bacteroids for the strain Rhizobium leguminosarum bv. viciae 3841.