Fixation In Soybean Research Articles

Non-CG DNA hypomethylation promotes photosynthesis and nitrogen fixation in soybean

Non-CG DNA methylation, a plant-specific epigenetic mark mainly regulated by chromomethylase (CMT), is known to play important roles in Arabidopsis thaliana. However, whether and to what extent non-CG DNA methylation modulates agronomic traits in crops remain to be explored. Here, we describe the consequences of non-CG DNA hypomethylation on development, seed composition, and yield in soybean (Glycine max). We created a Gmcmt mutant line lacking function of all four CMT genes. This line exhibited substantial hypomethylation of non-CG (CHG and CHH) sites. Non-CG hypomethylation enhanced chromatin accessibility and promoted or repressed the expression of hundreds of functionally relevant genes, including upregulation of GOLDEN-LIKE 10 (GmGLK10), which led to enhanced photosynthesis and, unexpectedly, improved nitrogen fixation efficiency. The Gmcmt line produced larger seeds with increased protein content. This study provides insights into the mechanisms of non-CG methylation-based epigenetic regulation of soybean development and suggests viable epigenetic strategies for improving soybean yield and nutritional value.

Nitrate Inhibits Nodule Nitrogen Fixation by Accumulating Ureide in Soybean Plants.

The mechanism by which nitrate inhibits nitrogen fixation in soybean (Glycine max L.) is not fully understood. Accumulation of ureide in soybean plant tissues may regulate the nitrogen fixation capacity through a feedback pathway. In this study, unilaterally nodulated dual-root soybeans prepared by grafting were grown in sand culture. They were subjected to the removal of the nodulated side roots, and were given either nitrate supply or no supply to the non-nodulated side roots for 3 days (experiment I). Additionally, they received nitrate supply to the non-nodulated side roots for 1-14 days (experiment II). The results showed that nitrate supply increased the levels of asparagine and ureide in soybean shoots (Experiment I). In Experiment II, nodule dry weight, nodule number, nodule nitrogenase activity, and nodule urate oxidase activity decreased significantly after 3, 7, and 14 days of nitrate supply. Ureide content in the shoots and nodules increased after 1, 3, and 7 days of nitrate supply, but decreased after 14 days of nitrate supply. There was a significant positive correlation between urate oxidase activity and nitrogenase activity. Hence, we deduced that nitrate supply increased the asparagine content in soybean shoots, likely inhibiting ureide degradation, which induced the accumulation of ureide in soybean shoots and nodules, and, in turn, feedback inhibited the nodule nitrogen fixation. In addition, urate oxidase activity can be used to assess the nitrogen fixation capacity of nodules.

Identification of loci associated with water use efficiency and symbiotic nitrogen fixation in soybean.

Soybean (Glycine max) production is greatly affected by persistent and/or intermittent droughts in rainfed soybean-growing regions worldwide. Symbiotic N2 fixation (SNF) in soybean can also be significantly hampered even under moderate drought stress. The objective of this study was to identify genomic regions associated with shoot carbon isotope ratio (δ13C) as a surrogate measure for water use efficiency (WUE), nitrogen isotope ratio (δ15N) to assess relative SNF, N concentration ([N]), and carbon/nitrogen ratio (C/N). Genome-wide association mapping was performed with 105 genotypes and approximately 4 million single-nucleotide polymorphism markers derived from whole-genome resequencing information. A total of 11, 21, 22, and 22 genomic loci associated with δ13C, δ15N, [N], and C/N, respectively, were identified in two environments. Nine of these 76 loci were stable across environments, as they were detected in both environments. In addition to the 62 novel loci identified, 14 loci aligned with previously reported quantitative trait loci for different C and N traits related to drought, WUE, and N2 fixation in soybean. A total of 58 Glyma gene models encoding for different genes related to the four traits were identified in the vicinity of the genomic loci.

Biological nitrogen fixation in soybean with different levels of drought tolerance

Biological nitrogen fixation in soybean with different levels of drought tolerance

Phosphorus and Potassium Cycling, Biological Nitrogen Fixation in Soybean, and Soil Microbial Activity in an Oxisol Fertilized with Wastewater from Heparin Production

Phosphorus and Potassium Cycling, Biological Nitrogen Fixation in Soybean, and Soil Microbial Activity in an Oxisol Fertilized with Wastewater from Heparin Production

A Review on Mitigation of Greenhouse Gases by Agronomic Practices towards Sustainable Agriculture

Agriculture is one among the sources of greenhouse gas emission in the World. Agriculture, being a prominent source of economic sectors in developing countries its impact on environmental climate changes both directly and indirectly through emission of greenhouse gases. To achieve reduced GHGs emissions in agriculture sector, there is a need to adopt climate smart activities and improved food and nutritional security to ensure a climate-smart sustainable agriculture. This short article explores the key ways to mitigate green house gases emissions in agriculture and critically highlights the potential for bacterial nitrogen fixation in soybean which is a recent approach. Symbiotic nitrogen fixation shows a great potential for GHGs mitigation while supporting the agriculture simultaneously. Other agronomic practices include tillage, residue management, rice field management, climate smart agriculture, organic farming and bio energy etc. This will help the farmers and other stakeholders to bring an environmentally friendly agriculture towards more ecological farming approach for future sustainability.

Biochar application increases biological nitrogen fixation in soybean with improved soil properties in an Ultisol

Biochar application increases biological nitrogen fixation in soybean with improved soil properties in an Ultisol

Soybean Seed Enrichment with Cobalt and Molybdenum as an Alternative to Conventional Seed Treatment

Biological nitrogen fixation in soybean is enhanced when seed is treated with cobalt (Co) and molybdenum (Mo) prior to planting. In this study, our objective was to verify if Co and Mo application during the reproductive phase of the crop increases seed Co and Mo concentration without adverse effects on seed quality. Two experiments were conducted. First, we investigated foliar and soil Co and Mo application under greenhouse conditions. Next, we validated the results obtained in the first study. The treatments for both experiments consisted of Co doses combined with Mo, and a control without Co and Mo application. The foliar application was more efficient in producing enriched Co and Mo seed; meanwhile, as Co doses increased so did Co and Mo concentrations in the seed. There were no adverse effects on nutrition, development, quality, and yield of parent plants and seed when these micronutrients were applied. The seed showed higher germination, vigor, and uniformity for the development of soybean seedlings. We concluded that the application of 20 g ha-1 Co and 800 g ha-1 Mo via foliar application at the reproductive stage of soybean increased germination rate and achieved the best growth and vigor index of enriched seed.

The effect of drought stress on nodulation, plant growth, and nitrogen fixation in soybean during early plant growth

AbstractSoybean [Glycine max (L.) Merr.] is one of the most important grain legume crops in the world. Soybean forms a symbiotic relationship with the nitrogen‐fixing rhizobia bacteria that reside in root nodules and fix atmospheric nitrogen. Most of the soybean's nitrogen demand is derived from symbiotic nitrogen fixation (SNF). Drought is becoming a major threat to crop production in the world. Legumes are sensitive to drought stress, and drought can negatively affect SNF, grain yield, and seed protein production. The effect of drought stress on soybean growth, morphological traits, nodulation, water use efficiency, and SNF, particularly during early plant growth, remains poorly characterized. We hypothesized that early‐onset drought stress can negatively affect nodulation, plant growth, and SNF in soybean during the vegetative growth stages. To test this hypothesis, a controlled‐environment study was conducted using soybean plants grown in pots, where plants were subjected to moderate drought stress (40% field capacity) and well‐watered (80% field capacity) from seeding until the flowering stage. Drought stress significantly reduced the nodule number and nodule dry weight, root and shoot biomass, shoot total nitrogen content, shoot carbon to nitrogen ratio, and shoot total fixed nitrogen compared to the well‐watered control. Conversely, root‐to‐shoot ratio and shoot nitrogen concentration were higher under drought stress compared to well‐watered conditions. These findings enhance our understanding of adverse impacts of drought in the early growth stage of soybean while suggesting that reduced total nitrogen assimilation during the vegetative phase can lead to less nitrogen reserves available for translocating at the seed filling stages for seed protein production. This information should aid in generating drought‐tolerant soybean cultivars.

A Nodule-Localized Small Heat Shock Protein GmHSP17.1 Confers Nodule Development and Nitrogen Fixation in Soybean

Small heat shock proteins (sHSPs) are ubiquitous proteins present in all organisms. The sHSPs are not only upregulated under heat shock as well as other stresses but also are expressed in unstressed cells, indicating quite diverse functions of sHSPs. However, there is little known about the role of sHSPs in nodulation and nitrogen fixation in soybean. In this study, we cloned a candidate protein of sHSP, GmHSP17.1, from proteome of nodule and analyzed its function in soybean nodulation. We found that GmHSP17.1 was a cytosolic protein and preferentially expressed during nodule development. An overexpression of GmHSP17.1 in composite transgenic plants showed increases in nodule number, fresh weight, nodule size, area of infection cells, and nitrogenase activity, and subsequently promoted the content of nitrogen and growth of soybean plants. While GmHSP17.1 RNA interference (RNAi) lines showed significantly impaired nodule development and nitrogen fixation efficiency. Through liquid chromatography-tandem mass spectrometry (LC-MS/MS), GmRIP1 was identified as the first potential target of GmHSP17.1, and was shown to be specifically expressed in soybean nodules. The interaction between GmHSP17.1 and GmRIP1 was further confirmed by yeast-two hybrid (Y2H), bimolecular fluorescence complementation (BiFC) in vivo and pull-down assay in vitro. Furthermore, peroxidase activity was markedly increased in GmHSP17.1 overexpressed nodules and decreased in RNAi lines. As a result, the reactive oxygen species (ROS) content greatly decreased in GmHSP17.1 overexpression lines and increased in suppression lines. Taken together, we conclude that GmHSP17.1 plays an important role in soybean nodulation through interacting with GmRIP1. Our results provide foundation for studying the mechanism of nitrogen fixation and for the genetics improvement of legume plants.

Increased nodular P level induced by intercropping stimulated nodulation in soybean under phosphorus deficiency

Low P availability is a vital constraint for nodulation and efficient N2 fixation of legume, including soybean. To elucidate the mechanisms involved in nodule adaption to low P availability under legume/cereal intercropping systems, two experiments consisting of three cropping patterns (monocropped soybean, monocropped maize, soybean/maize intercropping) were studied under both sufficient- and deficient-P levels. Our results demonstrated that intercropped soybean with maize showed a higher nodulation and N2 fixation efficiency under low P availability than monocropped soybean as evidenced by improvement in the number, dry weight and nitrogenase activity of nodules. These differences might be attributed to increase in P level in intercropping-induced nodules under low P supply, which was caused by the elevated activities of phytase and acid phosphatases in intercropping-induced nodules. Additionally, the enhanced expression of phytase gene in nodules supplied with deficient P level coincided with an increase in phytase and acid phosphatase activities. Our results revealed a mechanism for how intercropped maize stimulated nodulation and N2 fixation of soybean under P deficient environments, where enhanced synthesis of phytase and acid phosphatases in intercropping-induced nodules, and stimulated nodulation and N2 fixation.

SHORT-ROOT paralogs mediate feedforward regulation of D-type cyclin to promote nodule formation in soybean

Nitrogen fixation in soybean takes place in root nodules that arise from de novo cell divisions in the root cortex. Although several early nodulin genes have been identified, the mechanism behind the stimulation of cortical cell division during nodulation has not been fully resolved. Here we provide evidence that two paralogs of soybean SHORT-ROOT (GmSHR) play vital roles in soybean nodulation. Expression of GmSHR4 and GmSHR5 (GmSHR4/5) is induced in cortical cells at the beginning of nodulation, when the first cell divisions occur. The expression level of GmSHR4/5 is positively associated with cortical cell division and nodulation. Knockdown of GmSHR5 inhibits cell division in outer cortical layers during nodulation. Knockdown of both paralogs disrupts the cell division throughout the cortex, resulting in poorly organized nodule primordia with delayed vascular tissue formation. GmSHR4/5 function by enhancing cytokinin signaling and activating early nodulin genes. Interestingly, D-type cyclins act downstream of GmSHR4/5, and GmSHR4/5 form a feedforward loop regulating D-type cyclins. Overexpression of D-type cyclins in soybean roots also enhanced nodulation. Collectively, we conclude that the GmSHR4/5-mediated pathway represents a vital module that triggers cytokinin signaling and activates D-type cyclins during nodulation in soybean.

Biochar-Induced Soil Available Mo Enhancement to Increase Biological Nitrogen Fixation in Soybean in an Ultisol

Biochar-Induced Soil Available Mo Enhancement to Increase Biological Nitrogen Fixation in Soybean in an Ultisol

Regulation of Phosphorus Supply on Nodulation and Nitrogen Fixation in Soybean Plants with Dual-Root Systems

Phosphorus (P) is an important nutrient affecting nodulation and nitrogen fixation in soybeans. To further investigate the relationship of phosphorus with soybean nodulation and nitrogen fixation, the seedling grafting technique was applied in this study to prepare dual-root soybean systems for a sand culture experiment. From the unfolded cotyledon stage to the initial flowering stage, one side of each dual-root soybean system was irrigated with nutrient solution containing 1 mg/L, 31 mg/L, or 61 mg/L of phosphorus (phosphorus-application side), and the other side was irrigated with a phosphorus-free nutrient solution (phosphorus-free side), to study the effect of local phosphorus supply on nodulation and nitrogen fixation in soybean. The results are described as follows: (1) Increasing the phosphorus supply increased the nodules weight, nitrogenase activity, ureide content, number of bacteroids, number of infected cells, and relative expression levels of nodule nitrogen fixation key genes (GmEXPB2, GmSPX5, nifH, nifD, nifK, GmALN1, GmACP1, GmUR5, GmPUR5, and GmHIUH5) in root nodules on the phosphorus-application side. Although the phosphorus-application and phosphorus-free sides demonstrated similar changing trends, the phosphorus-induced increases were more prominent on the phosphorus-application side, which indicated that phosphorus supply systematically regulates nodulation and nitrogen fixation in soybean. (2) When the level of phosphorus supply was increased from 1 mg/L to 31 mg/L, the increase on the P– side root was significant, and nodule phosphorus content increased by 57.14–85.71% and 68.75–75.00%, respectively; ARA and SNA were 218.64–383.33% and 11.41–16.11%, respectively, while ureide content was 118.18–156.44%. When the level of phosphorus supply was increased from 31mg/L to 61mg/L, the increase in the regulation ability of root and nodule phosphorus content, ARA, SNA, and ureide content were low for roots, and the value for nodules was lower than when the phosphorus level increased from 1 mg/L to 31 mg/L. (3) A high-concentration phosphorus supply on one side of a dual-root soybean plant significantly increased the phosphorus content in the aboveground tissues, as well as the roots and nodules on both sides. In the roots on the phosphorus-free side, the nodules were prioritized for receiving the phosphorus transported from the aboveground tissues to maintain their phosphorus content and functionality.

Effects of maize and soybean intercropping on nodule growth, nitrogen fixation of soybean under low phosphorus condition

Effects of maize and soybean intercropping on nodule growth, nitrogen fixation of soybean under low phosphorus condition

A small heat shock protein, GmHSP17.9, from nodule confers symbiotic nitrogen fixation and seed yield in soybean

SummaryLegume–rhizobia symbiosis enables biological nitrogen fixation to improve crop production for sustainable agriculture. Small heat shock proteins (sHSPs) are involved in multiple environmental stresses and plant development processes. However, the role of sHSPs in nodule development in soybean remains largely unknown. In the present study, we identified a nodule‐localized sHSP, called GmHSP17.9, in soybean, which was markedly up‐regulated during nodule development. GmHSP17.9 was specifically expressed in the infected regions of the nodules. GmHSP17.9 overexpression and RNAi in transgenic composite plants and loss of function in CRISPR‐Cas9 gene‐editing mutant plants in soybean resulted in remarkable alterations in nodule number, nodule fresh weight, nitrogenase activity, contents of poly β‐hydroxybutyrate bodies (PHBs), ureide and total nitrogen content, which caused significant changes in plant growth and seed yield. GmHSP17.9 was also found to act as a chaperone for its interacting partner, GmNOD100, a sucrose synthase in soybean nodules which was also preferentially expressed in the infected zone of nodules, similar to GmHSP17.9. Functional analysis of GmNOD100 in composite transgenic plants revealed that GmNOD100 played an essential role in soybean nodulation. The hsp17.9 lines showed markedly more reduced sucrose synthase activity, lower contents of UDP‐glucose and acetyl coenzyme A (acetyl‐CoA), and decreased activity of succinic dehydrogenase (SDH) in the tricarboxylic acid (TCA) cycle in nodules due to the missing interaction with GmNOD100. Our findings reveal an important role and an unprecedented molecular mechanism of sHSPs in nodule development and nitrogen fixation in soybean.

An Overview of the Morphological, Genetic and Metabolic Mechanisms Regulating Phosphorus Efficiency Via Root Traits in Soybean

Phosphorus (P) is an essential macronutrient for optimum productivity of several crops including soybean, but it is largely limited in most arable lands. The persistent depletion of phosphate rocks is a major constraint for plant growth and development. Improved P efficiency (PE, uptake and use efficiency) drives an enhanced biological nitrogen fixation in soybean, which could consequently lead to an increased grain and biomass production. Thus, to mitigate P limitation in soybean production, a wide range of genetic approaches have been deployed. These approaches have unravelled the morphological, genetic, phytohormonal and metabolic mechanisms involved in soybean adaptations to P-deficient conditions. Most of the approaches are targeted at root modifications due to the importance of roots in the mediation of early responses to P-deficient conditions. PE among soybean genotypes in P-deficient conditions is mostly dependent on the root plasticity, development of shallow root architecture, symbiosis with arbuscular mycorrhizal fungi and exudation of phosphatases and organic acid anions. Genetic manipulation of soybean has revealed a number of important genes (GmPAPs, GmPTs, GmPLDZ2, GmIPS1 and GmExPB2), transcription factors (C2H2 zinc finger protein, WRKY and MYB) and quantitative trait loci (q14-2 and q19-2) modulating P mobilisation, uptake and utilization under P limiting conditions. Through the modification of root traits, the hormonal (biosynthesis, transport and secretion of ethylene, auxin and jasmonic acid) and metabolic (phenylpropanoid biosynthesis and phenylalanine metabolisms) pathways also modulate PE in soybean. Recent advances in genetic manipulations of root traits offer promising ways for enhancing soybean production, particularly in a P limiting environment.

Inoculation of arbuscular mycorrhizal fungi improve soil chemical properties, growth and symbiotic N2 -fixation in soybean (Glycine max L.) cultivars under field condition with low phosphorus availability

Inoculation of arbuscular mycorrhizal fungi improve soil chemical properties, growth and symbiotic N2 -fixation in soybean (Glycine max L.) cultivars under field condition with low phosphorus availability

Differential RNA Editing and Intron Splicing in Soybean Mitochondria during Nodulation.

Nitrogen fixation in soybean consumes a tremendous amount of energy, leading to substantial differences in energy metabolism and mitochondrial activities between nodules and uninoculated roots. While C-to-U RNA editing and intron splicing of mitochondrial transcripts are common in plant species, their roles in relation to nodule functions are still elusive. In this study, we performed RNA-seq to compare transcript profiles and RNA editing of mitochondrial genes in soybean nodules and roots. A total of 631 RNA editing sites were identified on mitochondrial transcripts, with 12% or 74 sites differentially edited among the transcripts isolated from nodules, stripped roots, and uninoculated roots. Eight out of these 74 differentially edited sites are located on the matR transcript, of which the degrees of RNA editing were the highest in the nodule sample. The degree of mitochondrial intron splicing was also examined. The splicing efficiencies of several introns in nodules and stripped roots were higher than in uninoculated roots. These include nad1 introns 2/3/4, nad4 intron 3, nad5 introns 2/3, cox2 intron 1, and ccmFc intron 1. A greater splicing efficiency of nad4 intron 1, a higher NAD4 protein abundance, and a reduction in supercomplex I + III2 were also observed in nodules, although the causal relationship between these observations requires further investigation.

Nodulation and biological nitrogen fixation in soybean (Glycine max L.) as influenced by phosphorus fertilization and arbuscular mycorrhizal inoculation

Abstract Arbuscular mycorrhizal fungi (AMF) can be used to promote the productivity of legumes on phosphorus- (P) deficient soils. The present study investigates the inoculation effects of three AMF species (Funneliformis mosseae, Rhizophagus intraradices, and Claroideoglomus etunicatum) and the control (uninoculated) on nitrogen fixation efficiency and growth performance of tropical soybean cultivar (TGx1448-2E) under varying P fertilizer rates (0, 20, and 40 kg P2O5 ha−1) in a derived savannah of Nigeria. The results showed that shoot and root dry matter, number of nodules, relative ureide abundance (RUA), nitrogen derived from atmosphere (Ndfa), total N fixed, shoot P uptake, grain, and biomass yield significantly increased with AMF inoculation, with better performance observed in plants inoculated with Rhizophagus intraradices and Funneliformis mosseae compared to Claroideoglomus etunicatum. Similarly, the soybean growth variables, P uptake, and nitrogen fixation activities increased with increasing P application rates. Conversely, AMF root colonization significantly reduced with increasing P rate. Interaction of AMF inoculation and P rates significantly influenced soybean growth and nitrogen fixation. R. intraradices inoculation with 20 kg P2O5 ha−1 resulted in the highest amount of RUA, Ndfa, N fixed, and grain yield. It could be concluded from this study that R. intraradices with moderate P rate could be used to enhance nodulation, nitrogen fixation, and soybean yield in P-deficient soils.