Project description:Background: The soil environment is responsible for sustaining most terrestrial plant life on earth, yet we know surprisingly little about the important functions carried out by diverse microbial communities in soil. Soil microbes that inhabit the channels of decaying root systems, the detritusphere, are likely to be essential for plant growth and health, as these channels are the preferred locations of new root growth. Understanding the microbial metagenome of the detritusphere and how it responds to agricultural management such as crop rotations and soil tillage will be vital for improving global food production. Methods: The rhizosphere soils of wheat and chickpea growing under + and - decaying root were collected for metagenomics sequencing. A gene catalogue was established by de novo assembling metagenomic sequencing. Genes abundance was compared between bulk soil and rhizosphere soils under different treatments. Conclusions: The study describes the diversity and functional capacity of a high-quality soil microbial metagenome. The results demonstrate the contribution of the microbiome from decaying root in determining the metagenome of developing root systems, which is fundamental to plant growth, since roots preferentially inhabit previous root channels. Modifications in root microbial function through soil management, can ultimately govern plant health, productivity and food security.
Project description:Increased root H+ secretion is known as a strategy of plant adaption to low phosphorus (P) stress by enhancing mobilization of sparingly soluble P-sources. However, it remains fragmentarywhether enhanced H+ exudation could reconstruct the plant rhizosphere microbial community under low P stress. The present study found that P deficiency led to enhanced H+ exudation from soybean (Glycine max) roots. Three out of all eleven soybean H+-pyrophosphatases (GmVP) geneswere up-regulated by Pi starvation in soybean roots. Among them, GmVP2 showed the highest expression level under low P conditions. Transient expression of a GmVP2-green fluorescent protein chimera in tobacco (Nicotiana tabacum) leaves, and functional characterization of GmVP2 in transgenic soybean hairy roots demonstrated that GmVP2 encoded a plasma membrane transporter that mediated H+ exudation. Meanwhile, GmVP2-overexpression in Arabidopsis thaliana resulted in enhanced root H+ exudation, promoted plant growth, and improved sparingly soluble Ca-P utilization. Overexpression of GmVP2 also changed the rhizospheric microbial community structures, as reflected by a preferential accumulation of acidobacteria in the rhizosphere soils. These results suggested that GmVP2 mediated Pi-starvation responsive H+ exudation,which is not only involved in plant growth and mobilization of sparingly soluble P-sources, but also affects microbial community structures in soils.
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: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:To dissect differences in gene expression profile of soybean roots and root nodules, we have employed microarray analysis. Seeds of soybean (Glycine max L. cv. Nourin No. 2) were inoculated with rhizobia (Bradyrhizobium diazoefficiens USDA110) and were hydroponically cultivated under controlled conditions with nitrogen free culture solution (Saito et al. 2014). At 19 days after planting, each plant were treated with or without 5 mM nitrate for 24 hours. Roots and nodules from three plants were pooled with three biological replications, and total RNA was extracted.
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: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.
Project description:Symbiotic legume nodules and lateral roots arise away from the root meristem via dedifferentiation events. While these organs share some morphological and developmental similarities, whether legume nodules are modified lateral roots is an open question. We dissected emerging nodules (EN), mature nodules (MN), emerging lateral roots (ELR) and young lateral roots (YLR), and constructed strand-specific RNAseq libraries using polyA-enriched RNA preparations. Root sections above and below these organs devoid of any lateral organs were used to construct respective control tissue libraries (ABEN, ABMN, ABELR, ABYLR respectively). High sequence quality, predominant mapping to coding sequences, and consistency between replicates indicated that the RNAseq libraries were of very high quality. We identified genes enriched in emerging nodules, mature nodules, emerging lateral roots and young lateral roots in soybean by comparing global gene expression profiles between each of these organs and adjacent root segments. Potential uses for this high quality transcriptome data set include generation of global gene regulatory networks to identify key regulators; metabolic pathway analyses and comparative analysis of key gene families to discover organ-specific biological processes; and identification of organ-specific alternate spliced transcripts. When combined with other similar datasets especially from leguminous plants these analyses can help answer questions on the evolutionary origins of root nodules and relationships between the development of different plant lateral organs.
Project description:Nuclei were isolated from soybean root nodules and proteins were purified. Trypsin digests from two preparations were analyzed by LC-MS/MS. GmFWL3, a member of the soybean GmFWL/CNR family, was identified. It encodes a microdomain-associated protein localized in both the nuclear and plasma membranes that regulates nodulation.