Light-sensitive short hypocotyl genes confer symbiotic nodule identity in the legume Medicago truncatula
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ABSTRACT:
ORGANISM(S): Medicago truncatula
PROVIDER: GSE211680 | GEO | 2025/02/06
REPOSITORIES: GEO
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Project description:Legumes establish endosymbiotic associations with nitrogen-fixing rhizobia, which they host inside root nodules. Here, specific physiological and morphological adaptations, such as the production of oxygen-binding leghemoglobin proteins and the formation of an oxygen diffusion barrier in the nodule periphery, are essential to protect the oxygen-labile bacterial nitrogenase enzyme. The molecular basis of the latter process remains elusive, as the identification of required genes is limited by the epistatic effect of nodule organogenesis over nodule infection and rhizobia accommodation. We overcame this by exploring the phenotypic diversity of Lotus japonicus accessions that uncouple nodule organogenesis from nodule infection when inoculated with a sub-compatible Rhizobium strain. Using comparative transcriptomics, we identified genes with functions associated with oxygen homeostasis and deposition of lipid polyesters on cell walls to be specifically upregulated in infected compared to uninfected nodules. As such hydrophobic modifications on cell walls are pivotal for creating diffusion barriers like the root endodermis, we focused on two Fatty acyl-CoA reductase genes that were specifically activated in the nodule or in the root endodermis. Mutant lines in a Fatty acyl-CoA reductase gene expressed exclusively in the nodule endodermis showed had decreased suberization of this cell layer and increased nodule permeability compared to wild type plants. Oxygen concentrations were significantly increased in the inner cortex of mutant nodules, which correlated with reduced nitrogen fixation rates, and impaired shoot growth. These results provide the first genetic evidence for the formation of the nodule oxygen diffusion barrier, a key adaptation enabling nitrogen fixation in legume nodules.
2022-11-01 | GSE216502 | GEO
Project description:During the legume-rhizobium symbiosis, free-living soil bacteria known as rhizobia trigger the formation of root nodules. The rhizobia infect these organs and adopt an intracellular lifestyle within the symbiotic nodule cells where they become nitrogen-fixing bacteroids. Several legume lineages enforce their symbionts into an extreme cellular differentiation, comprising cell enlargement and genome endoreduplication. The antimicrobial peptide transporter BclA is a major determinant of this differentiation process in Bradyrhizobium sp. ORS285, a symbiont of Aeschynomene spp.. In the absence of BclA, Bradyrhizobium sp. ORS285 proceeds until the intracellular infection of nodule cells but the bacteria cannot differentiate into enlarged polyploid bacteroids and fix nitrogen. The nodule bacteria of the bclA mutant constitute thus an intermediate stage between the free-living soil bacteria and the intracellular nitrogen-fixing bacteroids. Metabolomics on whole nodules of Aeschynomene afraspera and Aeschynomene indica infected with the ORS285 wild type or the bclA mutant revealed 47 metabolites that differentially accumulated concomitantly with bacteroid differentiation. Bacterial transcriptome analysis of these nodules discriminated nodule-induced genes that are specific to differentiated and nitrogen-fixing bacteroids and others that are activated in the host microenvironment irrespective of bacterial differentiation and nitrogen fixation. These analyses demonstrated that the intracellular settling of the rhizobia in the symbiotic nodule cells is accompanied with a first transcriptome switch involving several hundreds of upregulated and downregulated genes and a second switch accompanying the bacteroid differentiation, involving less genes but that are expressed to extremely elevated levels. The transcriptomes further highlighted the dynamics of oxygen and redox regulation of gene expression during nodule formation and we discovered that bclA represses the expression of non-ribosomal peptide synthetase gene clusters suggesting a non-symbiotic function of BclA. Together, our data uncover the metabolic and gene expression changes that accompany the transition from intracellular bacteria into differentiated nitrogen-fixing bacteroids.
2019-06-01 | GSE126971 | GEO
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.
2016-11-28 | GSE79811 | GEO
Project description:affy_med_2011_06 - affy_med_2011_06 - Legume plants establish a symbiotic interaction with soil bacteria called rhizobia. A complex molecular dialogue between the two partners is necessary for the successful infection and organogenesis processes that will ultimately result in the formation of a nitrogen fixing nodule. During a M. truncatula Tnt1 mutant screen, a new class of symbiotic mutant called noot (nodule root) was identified. This original single recessive mutant develops a root in apical position of nodules that are colonized by bacteria and functional for nitrogen fixation. This conversion suggests that the legume nodule morphogenetic pathway may be derived from a root program. We cloned the NOOT gene and showed that it corresponds to Pisum sativum COCH (Ferguson and Reid, 2005, Plant Cell Physiol 46, 1583-1589). The goal of this project is to compare the transcriptomes from wild type nodules and roots to the noot nodule one. This will allow us to unravel the similarity and differences between the wild type and mutant nodule transcriptomes but also to know which developmental pathway is under the control of the NOOT gene. --Seeds of the WT and noot mutant lines (two mutant alleles: Tnk507 and NF2717) were surface sterilized and placed at 4°C for three days on a minimal BNM medium square plate (12cm X 12cm). Seeds were germinated at room temperature and 10 seeds were placed in a row on nitrogen poor (BNM) plate. Seedlings were inoculated using Sinorhizobium meliloti Rm41 for nodule production. Some WT plants were not infected by the bacteria in order to collect roots. Nodules and roots were harvested 18 to 21 days post inoculation. Each experimental repetition (3 WT nodules, 3 WT roots and 2 mutant nodules of each allele) was harvested at a separated day. RNA preparations were done using a Quiagen Kit. 10 arrays - Medicago; gene knock out,organ comparison
2012-05-31 | E-GEOD-36558 | biostudies-arrayexpress
Project description:affy_med_2011_06 - affy_med_2011_06 - Legume plants establish a symbiotic interaction with soil bacteria called rhizobia. A complex molecular dialogue between the two partners is necessary for the successful infection and organogenesis processes that will ultimately result in the formation of a nitrogen fixing nodule. During a M. truncatula Tnt1 mutant screen, a new class of symbiotic mutant called noot (nodule root) was identified. This original single recessive mutant develops a root in apical position of nodules that are colonized by bacteria and functional for nitrogen fixation. This conversion suggests that the legume nodule morphogenetic pathway may be derived from a root program. We cloned the NOOT gene and showed that it corresponds to Pisum sativum COCH (Ferguson and Reid, 2005, Plant Cell Physiol 46, 1583-1589). The goal of this project is to compare the transcriptomes from wild type nodules and roots to the noot nodule one. This will allow us to unravel the similarity and differences between the wild type and mutant nodule transcriptomes but also to know which developmental pathway is under the control of the NOOT gene. --Seeds of the WT and noot mutant lines (two mutant alleles: Tnk507 and NF2717) were surface sterilized and placed at 4°C for three days on a minimal BNM medium square plate (12cm X 12cm). Seeds were germinated at room temperature and 10 seeds were placed in a row on nitrogen poor (BNM) plate. Seedlings were inoculated using Sinorhizobium meliloti Rm41 for nodule production. Some WT plants were not infected by the bacteria in order to collect roots. Nodules and roots were harvested 18 to 21 days post inoculation. Each experimental repetition (3 WT nodules, 3 WT roots and 2 mutant nodules of each allele) was harvested at a separated day. RNA preparations were done using a Quiagen Kit.
2012-06-01 | GSE36558 | GEO
Project description:The bacterium, Sinorhizobium meliloti, interacts symbiotically with leguminous plants such as Medicago truncatula to form nitrogen-fixing root nodules. During symbiosis, plant and bacterial cells differentiate in a coordinated manner, resulting in specialized plant cells that contain nitrogen-fixing bacteroids. Medicago nodules are organized in structurally distinct tissue zones, representing different stages of bacterial and plant differentiation. We used laser-capture microdissection (LCM) to analyze bacterial and plant gene expression in four root nodule regions. In parallel, we analyzed gene expression in nodules formed by wild type bacteria on six plant mutants with nitrogen fixation deficiencies (dnf). We found that bacteroid metabolism is drastically remodeled during bacteroid differentiation. Many processes required for bacterial growth are down-regulated in the nitrogen fixation zone. The overall transcriptional changes are similar to those occurring during nutrient limitation by the stringent response. We also observed differential expression of bacterial genes involved in nitrogen fixation, cell envelope homeostasis, cell division, stress response and polyamine biosynthesis at distinct stages of nodule development. In M. truncatula we observed the differential regulation of several host processes that may trigger bacteroid differentiation and control bacterial infection. We analyzed plant and bacterial gene expression simultaneously, which allowed us to correlate processes in both organisms.
2015-06-01 | GSE53705 | GEO
Project description:In agroecosystems, a plant-usable form of nitrogen is mainly generated by legume-based biological nitrogen fixation, a process that requires phosphorus (P) as an essential nutrient. To investigate the physiological mechanism whereby phosphorus influences soybean nodule nitrogen fixation, soybean root nodules were exposed to four phosphate levels: 1 mg/L (P stress), 11 mg/L (P stress), 31 mg/L (Normal P), 61 mg/L (High P) then proteome analysis of nodules was conducted to identify phosphorus-associated proteome changes. We found that phosphorus stress-induced ribosomal protein structural changes were associated with altered key root nodule protein synthesis profiles. Importantly, up-regulated expression of peroxidase was observed as an important phosphorus stress-induced nitrogen fixation-associated adaptation that supported two nodule-associated activities: scavenging of reactive oxygen species (ROS) and cell wall growth. In addition, phosphorus transporter (PT) and purple acid phosphatase (PAPs) were up-regulated that regulated phosphorus transport and utilisation to maintain phosphorus balance and nitrogen fixation function in phosphorus-stressed root nodules.
2022-08-11 | PXD033875 | Pride
Project description:Biological nitrogen fixation (BNF) is a primary input of nitrogen to natural and agricultural systems globally. BNF is a temperature-dependant enzymatic process and can be conducted by microbes (including Rhizobia) hosted symbiotically in root nodules of some plants. Heat shock proteins (Hsps) have been implicated in the process of acquiring thermotolerance or acclimating to elevated temperature, as they play a vital role in maintaining cell integrity and homeostasis during heat stress. Although the BNF response to temperature may crucially impact future ecosystem productivity in the face of global climate change, little is known about Hsp expression in nodules of N-fixing non-agricultural species, such as tropical N-fixing trees in the Fabaceae family. This project aimed to characterize small (15-20kDa) Hsp (sHsp) expression in nodule tissue to examine the biochemical mechanisms of heat response in these tissues. To first identify Hsps in nodule tissues, Vachellia farnesiana and Acacia confusa nodules were excised, heat shock was induced, and protein content was isolated via chemical treatment before separation of protein species and analysis with SDS-PAGE. Two polyacrylamide gels yielded bands in the 15-20 kDa region that displayed differential Coomassie staining, which were sent for further characterization by HPLC-MS analysis for protein sequencing. Ten rhizobial sHsps were detected in these samples in addition to seven Acacia sHsps when compared independently to reference rhizobial and plant proteome databases. In an attempt quantify relative expression of Hsps in nodule and root tissue, we performed western blot experiments using Anti-Hsp20 antibodies raised against human and mouse Hsp proteins, with anti-beta actin loading control. While nonuniform beta-actin expression across tissue types (A. confusa nodules versus root control) prevented quantitative analysis, the experiments validated that Hsp20s are expressed in Acacia nodules as well as in root tissue. These experiments could provide a foundation for future studies that aim to determine variation in responses to key stressors predicted to increase with global climate change and help determine the implications of warming across the tropics and beyond.
2024-10-09 | PXD055599 | Pride
Project description:Legumes interact with soil microbes, leading to the development of nitrogen-fixing root nodules and arbuscular mycorrhizal (AM) roots. While nodule initiation by diffusible lipochitooligosaccharide (LCO) Nod-factors of bacterial origin (Nod-LCOs) is well characterized, diffusible AM fungal signals were only recently identified as sulphated and non-sulphated LCOs (sMyc-LCOs and nsMyc-LCOs). Applying Myc-LCOs in parallel to Nod-LCOs, we used GeneChips to detail the global programme of gene expression in response to the external application of symbiotic LCOs.
2012-05-31 | GSE33636 | GEO
Project description:12plex_medicago_2012-03 - mtefd1 and wt roots and nodules - Identification of genes affected by a KO mutation in a transcription factor involved in root and nodule development, MtEFD1. - Comparison of wild type and efd-1 transcriptomes in non inoculated nitrogen-starved control roots and nodules at 4 dpi, 6 and 11 dpi. Comparison of wild type nodule (11 dpi) and root transcriptomes, using mixed random primed and polydT primed probes.
2019-10-16 | GSE138899 | GEO