Whole-Genome Transcriptional analysis of Sulfate and Sulfonate assimilation by Bradyrhizobium japonicum USDA 110
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ABSTRACT: The ability of Bradyrhizobium japonicum and B. elkanii strains to utilize alkane and aromatic sulfonates as sole sources of sulfur for growth was investigated. All of the strains tested were able to utilize alkane sulfonates, but not aromatic sulfonates for growth. Whole-genome transcriptional profiling was used to assess B. japonicum USDA 110 genes involved in growth on alkane sulfonates, as compared to growth on sulfate and cysteine. Two sets of genes, bll7007 to bll7011 and bll6449 to 6456 were highly expressed during growth with sulfate and sulfonates. These genes were predicted to encode alkanesulfonate monooxygenases and ABC transporter components. Reverse transcription-PCR (RT-PCR) analyses showed that these genes were organized in two operon-like structures and expressed as polycistronic messages. The sulfonate monooxygenase encoded by bll7010 (ssuD) complemented an E. coli mutant defective in utilization of sulfonates. The expression of many genes that were induced during growth on cysteine and taurine were under the control of the FixLJ-FixK2-FixK1 symbiotic nitrogen fixation cascade, indicating there is a novel linkage between sulfur metabolism and nitrogen fixation. Taken together, results of this study indicate that Bradyrhizobium sp. strains are metabolically diverse and likely use organosulfur compounds for growth and survival, and for legume nodulation and nitrogen fixation in soil systems. Three independent biological materials were prepared for sulfate or sulfonate supplemented cells. Total 12 arrays including dye swap were analyzed.
Project description:The ability of Bradyrhizobium japonicum and B. elkanii strains to utilize alkane and aromatic sulfonates as sole sources of sulfur for growth was investigated. All of the strains tested were able to utilize alkane sulfonates, but not aromatic sulfonates for growth. Whole-genome transcriptional profiling was used to assess B. japonicum USDA 110 genes involved in growth on alkane sulfonates, as compared to growth on sulfate and cysteine. Two sets of genes, bll7007 to bll7011 and bll6449 to 6456 were highly expressed during growth with sulfate and sulfonates. These genes were predicted to encode alkanesulfonate monooxygenases and ABC transporter components. Reverse transcription-PCR (RT-PCR) analyses showed that these genes were organized in two operon-like structures and expressed as polycistronic messages. The sulfonate monooxygenase encoded by bll7010 (ssuD) complemented an E. coli mutant defective in utilization of sulfonates. The expression of many genes that were induced during growth on cysteine and taurine were under the control of the FixLJ-FixK2-FixK1 symbiotic nitrogen fixation cascade, indicating there is a novel linkage between sulfur metabolism and nitrogen fixation. Taken together, results of this study indicate that Bradyrhizobium sp. strains are metabolically diverse and likely use organosulfur compounds for growth and survival, and for legume nodulation and nitrogen fixation in soil systems.
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:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. Transciptomic expression profiles indicated that genes involved in carbon/nitrogen metabolism, and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency. Bradyrhizobium japonicum strains were grown in the soybean rhizosphere under two different CO2 concentrations. Transcriptional profiling of B. japonicum was compared between cells grown under elevated CO2 and ambient conditions. Four biological replicates of each treatment were prepared, and four microarray slides were used for each strain.
Project description:To dissect differences in gene expression profile of soybean roots inoculated with wild-type and type III secretion mutant rhizobia, we have employed microarray analysis. Seeds of soybeans (Glycine max L. cv. Enrei and its non-nodulating line En1282) were surface-sterilized and germinated at 25 M-BM-0C for 2 days and were transferred to a plant box (CUL-JAR300; Iwaki, Tokyo, Japan) containing sterile vermiculite watered with B&D nitrogen-free medium (Broughton and Dilworth 1971). One day after transplant, each seedling was inoculated with Bradyrhizobium elkanii USDA61, its type III secretion mutant BerhcJ or sterilized water (mock treatment). Plants were cultivated in a growth chamber at 25M-BM-0C and 70% humidity with a daytime of 16 h followed by a nighttime of 8 h. To determine the gene expression, RNA was extracted from the roots 8 days after inoculation. Gene expression in soybean roots inoculated with Bradyrhizobium elkanii USDA61, its type III secretion mutant BerhcJ or sterilized water (mock treatment) was measured 8 days after inoculation. Three independent experiments were performed at each inoculation.
Project description:Arabidopsis thaliana transcriptome analysis in response to plant growth promoting rhizobacteria (PGPR)<br> Experiment 1 : Changes in gene expression profile triggered during root architecture response to Phyllobacterium.<br> Biological question : Which genes are up- or down-regulated in Arabidopsis thaliana cultivated in vitro with increased lateral root development in response to Phyllobacterium STM196 inoculation.<br> Experiment description: Seeds of wild-type Arabidopsis thaliana (ecotype Columbia) were surface-sterilized and sown on agar mineral medium (see below). 4 days after storage in the dark at 4C, seedling were cultivated 6 days in a growth chamber (16 h daily, 20-22C) and then transferred on a fresh agar mineral medium inoculated or not with Phyllobacterium STM196 (2.108 cfu/ml). 6 days later, root and leaves were collected, froze on liquid nitrogen and stored at -80C.<br> <br> Experiment 2 : Changes in gene expression profile triggered during induced systemic resistance (ISR)<br> Biological question : Which genes are up- or down-regulated during the ISR triggered by a rhizobacteria, in comparison with those affected by a pathogenic interaction. <br> Experiment description: Seeds were sown on 0.8% (W/V) agar mineral medium (see below). 4 days after storage in the dark at 4C, seedling were cultivated 6 days in a growth chamber (16 h daily, 20-22C) and then transferred on soil inoculated or not with 107 cfu.g-1 of Bradyrhizobium strain ORS278. Three weeks later, 3 leaves per plant were infiltrated with a suspension of Pseudomonas syringae pv. tomato (2.105 cfu.ml-1) or with MgSO4 10 mM alone for control plants. Infiltrated leaves were collected 24h later.<br> <br> Experiment 3 : Comparison of the effects of 3 rhizobacteria on Arabidopsis thaliana transcriptome<br> Biological question : which genes are specifically induced or repressed in Arabidopsis thaliana by inoculation of the soil with a PGPR vs a bacteria that has the ability to trigger nodule formation in a Legume. <br> Experiment description: Seeds of wild-type Arabidopsis thaliana (ecotype Columbia) were surface-sterilized and sown on agar mineral medium. Four days after storage in the dark at 4C, seedlings were cultivated 6 days in a growth chamber (16 h daily, 20-22C) and then transferred on soil inoculated or not with 108 cfu.g-1 of Mesorhizobium loti, or 108 cfu.g-1 of Phyllobacterium STM196, or 107 cfu.g-1 of Bradyrhizobium ORS278.
Project description:In this study, we combined metabolic reconstruction, growth assays, metabolome and transcriptome analyses to obtain a global view of the sulfur metabolic network and of the response to sulfur availability in Brevibacterium aurantiacum. In agreement with the growth of B. aurantiacum in the presence of sulfate and cystine, the metabolic reconstruction showed the presence of a sulfate assimilation pathway and of thiolation pathways that produce cysteine (cysE and cysK) or homocysteine (metX and metY) from sulfide, of at least one gene of the transsulfuration pathway (aecD) and of genes encoding three MetE-type methionine synthases. We also compared the expression profiles of B. aurantiacum ATCC9175 during sulfur starvation and in the presence of sulfate, cystine or methionine plus cystine. In sulfur starvation, 690 genes including 21 genes involved in sulfur metabolism and 29 genes encoding amino acids and peptide transporters were differentially expressed. We also investigated changes in pools of sulfur-containing metabolites and in expression profiles after growth in the presence of sulfate, cystine or methionine plus cystine. The expression of genes involved in sulfate assimilation and cysteine synthesis was repressed in presence of cysteine, while the expression of metX, metY, metE1, metE2 and BL613 encoding a probable cystathionine-γ-synthase decreased in the presence of methionine. We identified three ABC transporters: two stronger transcribed during cysteine limitation and one during methionine depletion. Finally, the expression of genes encoding a methionine γ-lyase, BL929, and a methionine transporter (metPS) was induced in the presence of methionine, in conjunction with a significant increase of volatile sulfur compounds production. Refer to individual Series. This SuperSeries is composed of the following subset Series: GSE25418: BA-Methionine plus Cystine vs Cystine GSE25419: BA-Sulfate vs Cystine GSE25420: BA-Methionine plus Cystine vs Sulfate GSE25421: BA-Sulfate vs Sulfate starvation
Project description:To dissect differences in gene expression profile of soybean roots inoculated with wild-type and type III secretion mutant rhizobia, we have employed microarray analysis. Seeds of soybean (Glycine max L. cv. BARC-2 (Rj4/Rj4)) were surface-sterilized and germinated at 25 °C for 2 days and were transferred to the seed pack (Seed Pack; Daiki rika Kogyo Co., Ltd., Shiga, Japan) watered with B&D nitrogen-free medium (Broughton and Dilworth 1971). One day after transplant, each seedling was inoculated with Bradyrhizobium elkanii USDA61 or its type III secretion mutant BErhcJ. Plants were cultivated in a growth chamber at 25°C and 70% humidity with a daytime of 16 h followed by a nighttime of 8 h. To determine the gene expression, RNA was extracted from the roots 2 and 4 days after inoculation. Gene expression in soybean roots inoculated with Bradyrhizobium elkanii USDA61, its type III secretion mutant BErhcJ was measured 2 and 4 days after inoculation. Three independent experiments were performed at each inoculation.
Project description:Bradyrhizobia are common members of soil microbiomes and known as N2-fixing symbionts of economically important legumes. Many are also denitrifiers, which can act as sinks or sources for N2O. Inoculation with compatible rhizobia is often needed for optimal N2-fixation, but the choice of inoculant may have consequences for N2O emission. Here, we determined the phylogeny and denitrification capacity of Bradyrhizobium strains, most of them isolated from peanut-nodules. Analyses of genomes and denitrification end-points showed that all were denitrifiers, but only ~1/3 could reduce N2O. The N2O-reducing isolates had strong preference for N2O- over NO3--reduction. Such preference was also observed in a study of other bradyrhizobia and tentatively ascribed to competition between the electron pathways to Nap (periplasmic NO3- reductase) and Nos (N2O reductase). Another possible explanation is lower abundance of Nap than Nos. Here, proteomics revealed that Nap was instead more abundant than Nos, supporting the hypothesis that the electron pathway to Nos outcompetes that to Nap. In contrast, Paracoccus denitrificans, which has membrane-bond NO3- reductase (Nar), reduced N2O and NO3- simultaneously. We propose that the control at the metabolic level, favoring N2O reduction over NO3- reduction, applies also to other denitrifiers carrying Nos and Nap but lacking Nar.
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>