Transcriptional and Physiological Responses of Bradyrhizobium japonicum to Desiccation-Induced Stress
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ABSTRACT:
SUBMITTER: Cytryn E
PROVIDER: S-EPMC2168615 | biostudies-literature | 2007 Dec
REPOSITORIES: biostudies-literature
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Project description:The growth and persistence of rhizobia and bradyrhizobia in soils are negatively impacted by drought conditions. In this study, we used genome-wide transcriptional analyses to obtain a comprehensive understanding of the response of Bradyrhizobium japonicum to drought. Desiccation of cells resulted in the differential expression of 15 to 20% of the 8,453 [corrected] B. japonicum open reading frames, with considerable differentiation between early (after 4 h) and late (after 24 and 72 h) expressed genes. While 225 genes were universally up-regulated at all three incubation times in response to desiccation, an additional 43 and 403 up-regulated genes were common to the 4/24- and 24/72-h incubation times, respectively. Desiccating conditions resulted in the significant induction (>2.0-fold) of the trehalose-6-phosphate synthetase (otsA), trehalose-6-phosphate phosphatase (otsB), and trehalose synthase (treS) genes, which encode two of the three trehalose synthesis pathways found in B. japonicum. Gene induction was correlated with an elevated intracellular concentration of trehalose and increased activity of trehalose-6-phosphate synthetase, collectively supporting the hypothesis that this disaccharide plays a prominent and important role in promoting desiccation tolerance in B. japonicum. Microarray data also indicated that sigma(54)- and sigma(24)-associated transcriptional regulators and genes encoding isocitrate lyase, oxidative stress responses, the synthesis and transport of exopolysaccharides, heat shock response proteins, enzymes for the modification and repair of nucleic acids, and the synthesis of pili and flagella are also involved in the response of B. japonicum to desiccation. Polyethylene glycol-generated osmotic stress induced significantly fewer genes than those transcriptionally activated by desiccation. However, 67 genes were commonly induced under both conditions. Taken together, these results suggest that B. japonicum directly responds to desiccation by adapting to changes imparted by reduced water activity, such as the synthesis of trehalose and polysaccharides and, secondarily, by the induction of a wide variety of proteins involved in protection of the cell membrane, repair of DNA damage, stability and integrity of proteins, and oxidative stress responses.
| S-EPMC2045231 | biostudies-literature
Project description:The growth and persistence of rhizobia and bradyrhizobia in soils are negatively impacted by drought conditions. In this study, we used genome-wide transcriptional analyses to obtain a comprehensive understanding of the response of Bradyrhizobium japonicum to drought. Desiccation of cells resulted in the differential expression of 15 to 20% of the 8,480 B. japonicum open reading frames, with considerable differentiation between early (after 4 h) and late (after 24 and 72 h) expressed genes. While 225 genes were universally up-regulated at all three incubation times in response to desiccation, an additional 43 and 403 up-regulated genes were common to the 4/24- and 24/72-h incubation times, respectively. Desiccating conditions resulted in the significant induction (>2.0-fold) of the trehalose-6-phosphate synthetase (otsA), trehalose-6-phosphate phosphatase (otsB), and trehalose synthase (treS) genes, which encode two of the three trehalose synthesis pathways found in B. japonicum. Gene induction was correlated with an elevated intracellular concentration of trehalose and increased activity of trehalose-6-phosphate synthetase, collectively supporting the hypothesis that this disaccharide plays a prominent and important role in promoting desiccation tolerance in B. japonicum. Microarray data also indicated that sigma(54)- and sigma(24)-associated transcriptional regulators and genes encoding isocitrate lyase, oxidative stress responses, the synthesis and transport of exopolysaccharides, heat shock response proteins, enzymes for the modification and repair of nucleic acids, and the synthesis of pili and flagella are also involved in the response of B. japonicum to desiccation. Polyethylene glycol-generated osmotic stress induced significantly fewer genes than those transcriptionally activated by desiccation. However, 67 genes were commonly induced under both conditions. Taken together, these results suggest that B. japonicum directly responds to desiccation by adapting to changes imparted by reduced water activity, such as the synthesis of trehalose and polysaccharides and, secondarily, by the induction of a wide variety of proteins involved in protection of the cell membrane, repair of DNA damage, stability and integrity of proteins, and oxidative stress responses. Keywords: stress response; time course
2007-09-25 | GSE9125 | GEO
Project description:The rhizobial bacterium Bradyrhizobium japonicum functions as a nitrogen-fixing symbiont of the soybean plant (Glycine max). Plants are capable of producing an oxidative burst, a rapid proliferation of reactive oxygen species (ROS), as a defense mechanism against pathogenic and symbiotic bacteria. Therefore, B. japonicum must be able to resist such a defense mechanism to initiate nodulation. In this study, paraquat, a known superoxide radical-inducing agent, was used to investigate this response. Genome-wide transcriptional profiles were created for both prolonged exposure (PE) and fulminant shock (FS) conditions. These profiles revealed that 190 and 86 genes were up- and downregulated for the former condition, and that 299 and 105 genes were up- and downregulated for the latter condition, respectively (>2.0-fold; P < 0.05). Many genes within putative operons for F(0)F(1)-ATP synthase, chemotaxis, transport, and ribosomal proteins were upregulated during PE. The transcriptional profile for the FS condition strangely resembled that of a bacteroid condition, including the FixK(2) transcription factor and most of its response elements. However, genes encoding canonical ROS scavenging enzymes, such as superoxide dismutase and catalase, were not detected, suggesting constitutive expression of those genes by endogenous ROS. Various physiological tests, including exopolysaccharide (EPS), cellular protein, and motility characterization, were performed to corroborate the gene expression data. The results suggest that B. japonicum responds to tolerable oxidative stress during PE through enhanced motility, increased translational activity, and EPS production, in addition to the expression of genes involved in global stress responses, such as chaperones and sigma factors.
| S-EPMC3127611 | biostudies-other
Project description:Differential gene expression was analyzed between B. japonicum wild type (Bj110) and aceA mutant (BjΔaceA) exposed to desiccation stress to find AceA regulons under the culture condition.
2015-07-21 | GSE69999 | GEO
Project description:Trehalose, a disaccharide accumulated by many microorganisms, acts as a protectant during periods of physiological stress, such as salinity and desiccation. Previous studies reported that the trehalose biosynthetic genes (otsA, treS, and treY) in Bradyrhizobium japonicum were induced by salinity and desiccation stresses. Functional mutational analyses indicated that disruption of otsA decreased trehalose accumulation in cells and that an otsA treY double mutant accumulated an extremely low level of trehalose. In contrast, trehalose accumulated to a greater extent in a treS mutant, and maltose levels decreased relative to that seen with the wild-type strain. Mutant strains lacking the OtsA pathway, including the single, double, and triple DeltaotsA, DeltaotsA DeltatreS and DeltaotsA DeltatreY, and DeltaotsA DeltatreS DeltatreY mutants, were inhibited for growth on 60 mM NaCl. While mutants lacking functional OtsAB and TreYZ pathways failed to grow on complex medium containing 60 mM NaCl, there was no difference in the viability of the double mutant strain when cells were grown under conditions of desiccation stress. In contrast, mutants lacking a functional TreS pathway were less tolerant of desiccation stress than the wild-type strain. Soybean plants inoculated with mutants lacking the OtsAB and TreYZ pathways produced fewer mature nodules and a greater number of immature nodules relative to those produced by the wild-type strain. Taken together, results of these studies indicate that stress-induced trehalose biosynthesis in B. japonicum is due mainly to the OtsAB pathway and that the TreS pathway is likely involved in the degradation of trehalose to maltose. Trehalose accumulation in B. japonicum enhances survival under conditions of salinity stress and plays a role in the development of symbiotic nitrogen-fixing root nodules on soybean plants.
| S-EPMC2820964 | biostudies-literature
Project description:Bradyrhizobium japonicum is a nitrogen-fixing symbiont of soybean. In previous studies, transcriptomic profiling of B. japonicum USDA110, grown under various environmental conditions, revealed the highly induced gene aceA, encoding isocitrate lyase (ICL). The ICL catalyzes the conversion of isocitrate to succinate and glyoxylate in the glyoxylate bypass of the TCA cycle. Here, we evaluated the functional role of B. japonicum ICL under desiccation-induced stress conditions. We purified AceA (molecular mass = 65 kDa) from B. japonicum USDA110, using a His-tag and Ni-NTA column approach, and confirmed its ICL enzyme activity. The aceA mutant showed higher sensitivity to desiccation stress (27% relative humidity (RH)), compared to the wild type. ICL activity of the wild type strain increased approximately 2.5-fold upon exposure to 27% RH for 24 h. The aceA mutant also showed an increased susceptibility to salt stress. Gene expression analysis of aceA using qRT-PCR revealed a 148-fold induction by desiccation, while other genes involved in the glyoxylate pathway were not differentially expressed in this condition. Transcriptome analyses revealed that stress-related genes, such as chaperones, were upregulated in the wild-type under desiccating conditions, even though fold induction was not dramatic (ca. 1.5-2.5-fold).
| S-EPMC4519974 | biostudies-literature
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizoplane and rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizoplane and rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizoplane of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that elevated atmospheric CO2 concentration indirectly influenced the expression of a large number of genes in Bradyrhizobium attached to soybean roots. In addition, relative to plants and bacteria grown under ambient CO2 growth conditions, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere. The expression profile of genes involved in lipochitooligosaccharide 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, the results of these studies indicate that the growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizoplane, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency.
| S-EPMC4070659 | biostudies-literature
Project description:A genome-wide transcriptional profile of Bradyrhizobium japonicum, the nitrogen-fixing endosymbiont of the soybean plant, revealed differential expression of approximately 15% of the genome after a 1 mM treatment with the phytohormone indole-3-acetic acid (IAA). A total of 1,323 genes were differentially expressed (619 up-regulated and 704 down-regulated) at a two-fold cut off with q value ≤ 0.05. General stress response genes were induced, such as those involved in response to heat, cold, oxidative, osmotic, and desiccation stresses and in exopolysaccharide (EPS) biosynthesis. This suggests that IAA is effective in activating a generalized stress response in B. japonicum. The transcriptional data were corroborated by the finding that stress tolerance of B. japonicum in cell viability assays was enhanced when pre-treated with 1 mM IAA compared to controls. The IAA treatment also stimulated biofilm formation and EPS production by B. japonicum, especially acidic sugar components in the total EPS. The IAA pre-treatment did not influence the nodulation ability of B. japonicum. The data provide a comprehensive overview of the potential transcriptional responses of the symbiotic bacterium when exposed to the ubiquitous hormone of its plant host.
| S-EPMC3788728 | biostudies-literature
Project description:Bradyrhizobium japonicum is a facultative chemoautotroph capable of utilizing hydrogen gas as an electron donor in a respiratory chain terminated by oxygen to provide energy for cellular processes and carbon dioxide assimilation via a reductive pentose phosphate pathway. A transcriptomic analysis of B. japonicum cultured chemoautotrophically identified 1,485 transcripts, representing 17.5% of the genome, as differentially expressed when compared to heterotrophic cultures. Genetic determinants required for hydrogen utilization and carbon fixation, including the uptake hydrogenase system and components of the Calvin-Benson-Bassham cycle, were strongly induced in chemoautotrophically cultured cells. A putative isocitrate lyase (aceA; blr2455) was among the most strongly upregulated genes, suggesting a role for the glyoxylate cycle during chemoautotrophic growth. Addition of arabinose to chemoautotrophic cultures of B. japonicum did not significantly alter transcript profiles. Furthermore, a subset of nitrogen fixation genes was moderately induced during chemoautotrophic growth. In order to specifically address the role of isocitrate lyase and nitrogenase in chemoautotrophic growth, we cultured aceA, nifD, and nifH mutants under chemoautotrophic conditions. Growth of each mutant was similar to that of the wild type, indicating that the glyoxylate bypass and nitrogenase activity are not essential components of chemoautotrophy in B. japonicum.
| S-EPMC2566215 | biostudies-literature
Project description:Expression data from B. japonicum stress response; aerobic treatment of B. japoncium culture under different stress conditons; pH stress (8 and 4; 4 h); salt stress (80 mM NaCl; 4 h); heat shock (43 °C; 15 min) and temperature stress (35.2 °C; 48 h); as reference wildtype without treatment (AG media; pH 6.9; without NaCl; 28 °C) was used heat shock data were verified by using rpoH-mutant strains B. japonicum 5009; B. japonicum 5032 and B. japonicum 09-32 as described in Narberhaus et al. 1997
2019-12-23 | GSE22388 | GEO