Project description:The transition metal tungsten (W) finds increasing application in military, aviation and household appliance industry, opening new paths for the heavy metal into the environment. Since tungsten shares certain chemical properties with the essential plant micro nutrient molybdenum, it is proposed to inhibit enzymatic activity of molybdoenzymes by replacing the Mo-ion bound to the co-factor. However, recent studies suggest the inhibition of enzymatic activity might not be the only effect W has on plants and that, much like other heavy metals, tungsten exerts toxicity on its own. Still, our understanding of the mechanisms behind the apparent phytotoxicity remains limited.This study investigates the effects of W on growth, nutrient levels (ionome, ICP-MS), starch levels and nitrogen nutrition (IRMS, enzyme activity assays) as well as root and nodule proteome (LC-MS/MS) of Glycine max cv. Primus. Plants were inoculated with Bradyrhizobium japonicum and grown in a semi hydroponic set up using three different tungsten concentrations (zero, 0.1 mM and 0.5 mM). To identify possible benefits of a functional bacterial symbiosis on W induced stress response, two different environmental growth conditions, one with suppressed N-fixation, supplied with Nitrate (10 mM KNO3) and one solely relying on symbiotic N-fixation (zero KNO3), were applied. Glycine max was able to take up considerable amounts of W (703 ± 136 mg kg-1). However, high W resulted in a strong reduction of shoot biomass of both N regimes and of root biomass (N fed only). Irrespective of N regime, NR activity and total N decreased with increasing W concentrations. Similarly, nitrogenase precursor levels as well as N2-fixation, nodule fixation activity (mg N g-1 nodule dry weight) and nodulation were reduced, indicating that nitrogenase synthesis and activity were negatively affected by W stress. However, along a N fix nodule specific induction of the secondary and phytohormone metabolism, it appears that N2 fixation of remaining nodules was not as severely affected by increasing levels of tungsten than nitrate reduction. Besides N metabolism, plants exhibited an imbalance in nutrient and a failure of carbon metabolic pathways accompanied by an accumulation of starch at high tungsten concentrations, independent of N-regime. Proteomic data demonstrated that the response to high W concentrations is independent of nodule functionality and dominated by several peroxidases and other general stress related proteins. Based on an evaluation of several W responsive proteotypic peptides, we identified a set of protein markers of W stress and possible targets for improved stress tolerance.
Project description:Legumes interact with nodulating bacteria that convert atmospheric nitrogen into ammonia for plant use. This nitrogen fixation takes place within root nodules that form after infection of root hairs by compatible rhizobia. Using cDNA microarrays, we monitored gene expression in soybean (Glycine max) inoculated with the nodulating bacterium Bradyrhizobium japonicum 4, 8, and 16 days after inoculation (dai), time points that coincided with nodule development and the onset of nitrogen fixation. This experiment identified several thousand genes that were differentially expressed in response to B. japonicum inoculation. Expression of 27 genes was analyzed by qRT-PCR and their expression patterns mimicked the microarray results confirming integrity of analyses. The microarray results suggest that B. japonicum reduces plant defense responses during nodule development. In addition, the data revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational, post-translational) that is likely essential for development of the symbiosis and adjustment to an altered nutritional status. Keywords = symbiosis Keywords = nodulation Keywords = rhizobium Keywords = defense Keywords = ANOVA Keywords = plant loop design, 7 samples, 7 comparison, 2 technical repeats including dye swaps, 4 biological repeats
Project description:Analysis of a mutant in the Bradyrhizobium japonicum response regulator RegR. RegR is known to control expression of the gene encoding the key regulator of nitrogen fixation NifA. This study provides insights into the RegR regulon under free-living conditions and during symbiosis. Cells of the regR mutant and the wild type were grown to mid-exponential phase in full medium (PSY) under different oxygen conditions (aerobic and microaerobic) in culture. Nodules from soybean plant infected with the regR mutant or the wild type were collected 13 and 21 days post inoculation To determine genes under control of RegR during symbiosis. This study includes also the samples GSM210238 to GSM210286. Keywords: genetic modification, time course, growth conditions
Project description:pc_arcole - arcole / pgpr - What are the genes implicated in the efficiency of nitrogenous nutrition when A.thaliana is inoculated with a PGPR (Plant Growth Promoting Rhizobacteria)? - A.thaliana seeds germinated and grew during ten days until they were transfered in 6 different media: 0,5 mM nitrate with PGPR (Plant Growth Promoting Rhizobacteria), 0,5mM nitrate without PGPR, 2mM nitrate with PGPR, 2mM nitrate without PGPR, 20 mM nitrate with PGPR, 20 mM nitrate without PGPR. Young plantlets grew 7 days in these new mediums. Shoots are collected in eppendorf. 6 dye-swap - dose response,organ comparison,treated vs untreated comparison
Project description:Although N2 fixation can occur in free-living cyanobacteria, the unicellular endosymbiotic cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) is considered to be a dominant N2-fixing species in marine ecosystems. Four UCYN-A sublineages are known from partial nitrogenase (nifH) gene sequences. However, few studies have investigated their habitat preferences and regulation by their respective hosts in open-ocean versus coastal environments. Here, we compared UCYN-A transcriptomes from oligotrophic open-ocean versus nutrient-rich coastal waters. UCYN-A1 metabolism was more impacted by habitat changes than UCYN-A2. However, across habitats and sublineages genes for nitrogen fixation and energy production were highly transcribed. Curiously these genes, critical to the symbiosis for the exchange of fixed nitrogen for fixed carbon, maintained the same schedule of diel expression across habitats and UCYN-A sublineages, including UCYN-A3 in the open-ocean transcriptomes. Our results undersore the importance of nitrogen fixation in UCYN-A symbioses across habitats, with consequences for community interaction and global biogeochemical cycles.
Project description:pc_arcole - arcole / pgpr - What are the genes implicated in the efficiency of nitrogenous nutrition when A.thaliana is inoculated with a PGPR (Plant Growth Promoting Rhizobacteria)? - A.thaliana seeds germinated and grew during ten days until they were transfered in 6 different media: 0,5 mM nitrate with PGPR (Plant Growth Promoting Rhizobacteria), 0,5mM nitrate without PGPR, 2mM nitrate with PGPR, 2mM nitrate without PGPR, 20 mM nitrate with PGPR, 20 mM nitrate without PGPR. Young plantlets grew 7 days in these new mediums. Shoots are collected in eppendorf.
Project description:Legumes interact with nodulating bacteria that convert atmospheric nitrogen into ammonia for plant use. This nitrogen fixation takes place within root nodules that form after infection of root hairs by compatible rhizobia. Using cDNA microarrays, we monitored gene expression in soybean (Glycine max) inoculated with the nodulating bacterium Bradyrhizobium japonicum 4, 8, and 16 days after inoculation (dai), time points that coincided with nodule development and the onset of nitrogen fixation. This experiment identified several thousand genes that were differentially expressed in response to B. japonicum inoculation. Expression of 27 genes was analyzed by qRT-PCR and their expression patterns mimicked the microarray results confirming integrity of analyses. The microarray results suggest that B. japonicum reduces plant defense responses during nodule development. In addition, the data revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational, post-translational) that is likely essential for development of the symbiosis and adjustment to an altered nutritional status. Keywords = symbiosis Keywords = nodulation Keywords = rhizobium Keywords = defense Keywords = ANOVA Keywords = plant Keywords: nodulating vs not nodulating
Project description:<p>Biological nitrogen fixation by free-living bacteria and rhizobial symbiosis with legumes plays a key role in sustainable crop production. Here, we study how different crop combinations influence the interaction between peanut plants and their rhizosphere microbiota via metabolite deposition and functional responses of free-living and symbiotic nitrogen-fixing bacteria. Based on a long-term (8 year) diversified cropping field experiment, we find that peanut co-cultured with maize and oilseed rape lead to specific changes in peanut rhizosphere metabolite profiles and bacterial functions and nodulation. Flavonoids and coumarins accumulate due to the activation of phenylpropanoid biosynthesis pathways in peanuts. These changes enhance the growth and nitrogen fixation activity of free-living bacterial isolates, and root nodulation by symbiotic Bradyrhizobium isolates. Peanut plant root metabolites interact with Bradyrhizobium isolates contributing to initiate nodulation. Our findings demonstrate that tailored intercropping could be used to improve soil nitrogen availability through changes in the rhizosphere microbiome and its functions.</p>
Project description:Plant growth-promoting rhizobacteria (PGPR) are soil beneficial microorganisms that colonize plant roots for nutritional purposes and accordingly benefit plants by increasing plant growth or reducing disease. But it still remains unclear which mechanisms or pathways are involved in the interactions between PGPR and plants. To understand the complex plant-PGPR interactions, the changes in the transcriptome of typical PGPR standard Bacillus subtilis in responding to rice seedlings were analyzed.