Nitrogen Metabolism In Plants Research Articles

Circadian Rhythm and Nitrogen Metabolism Participate in the Response of Boron Deficiency in the Root of Brassica napus

Boron (B) deficiency has been shown to inhibit root cell growth and division. However, the precise mechanism underlying B deficiency-mediated root tip growth inhibition remains unclear. In this study, we investigated the role of BnaA3.NIP5;1, a gene encoding a boric acid channel, in Brassica napus (B. napus). BnaA3.NIP5;1 is expressed in the lateral root cap and contributes to B acquisition in the root tip. Downregulation of BnaA3.NIP5;1 enhances B sensitivity in B. napus, resulting in reduced shoot biomass and impaired root tip development. Transcriptome analysis was conducted on root tips from wild-type B. napus (QY10) and BnaA3.NIP5;1 RNAi lines to assess the significance of B dynamics in meristematic cells during seedling growth. Differentially expressed genes (DEGs) were significantly enriched in plant circadian rhythm and nitrogen (N) metabolism pathways. Notably, the circadian-rhythm-related gene HY5 exhibited a similar B regulation pattern in Arabidopsis to that observed in B. napus. Furthermore, Arabidopsis mutants with disrupted circadian rhythm (hy5/cor27/toc1) displayed heightened sensitivity to low B compared to the wild type (Col-0). Consistent with expectations, B deficiency significantly disrupted N metabolism in B. napus roots, affecting nitrogen concentration, nitrate reductase enzyme activity, and glutamine synthesis. Interestingly, this disruption was exacerbated in BnaA3NIP5;1 RNAi lines. Overall, our findings highlight the critical role of B dynamics in root tip cells, impacting circadian rhythm and N metabolism, ultimately leading to retarded growth. This study provides novel insights into B regulation in root tip development and overall root growth in B. napus.

Vertical non-uniform distribution of soil salinity enhances nitrogen utilization efficiency and influences δ15N distribution in tomato plants

Soil salinity typically exhibits non-uniform distribution in the natural environment. However, how vertically non-uniform distribution of soil salinity in the root zone (VNDSR) regulated plant nitrogen metabolism is still largely elusive. This study aimed to investigate the impact of VNDSR on leaf Malondialdehyde (MDA) content, upper and lower root activity, leaf Na+/Ca2+ and Na+/K+, various tomato organs’ nitrogen concentration (%) and natural abundance of nitrogen isotopes (δ15N,‰), and nitrogen utilization efficiency of tomato plants. Four treatments were established, including the upper layer of the root zone having soil salinity levels of 1 ‰, 1 ‰, 2 ‰, and 3 ‰, while the corresponding lower layer of the root zone had soil salinity levels of 1 ‰, 5 ‰, 4 ‰, and 3 ‰, respectively, denoted as T1:1, T1:5, T2:4, and T3:3. The results showed that under the same average soil salinity conditions and compared to the treatment with uniform soil salinity distribution in the root zone (T3:3), the VNDSR treatment (T1:5) significantly reduced leaf MDA content (p < 0.01), Na+/Ca2+ (p < 0.01) and Na+/K+ (p < 0.01), and stem δ15N values (p < 0.05). Moreover, the VNDSR treatment (T1:5) significantly increased the ratio of upper and lower root biomass-weighted root activity (p < 0.01), tomato fruit yield (p < 0.01), and nitrogen partial factor productivity (PFP, gg−1, p < 0.01) compared to uniform salt distribution treatment (T3:3). There were significant positive correlations (p < 0.05) between leaf δ15N values and Nitrogen Absorption Ratio (NAR, %, p < 0.05) and PFP (p < 0.05), indicating that under VNDSR, δ15N values can serve as an indicator that comprehensively reflects the information of plant nitrogen utilization efficiency. In conclusion, the VNDSR could mitigate the damage of salt stress to tomatoes, enhance plant nitrogen uptake and utilization efficiency, and promote the growth and development of tomatoes. Data AvailabilityThe datasets generated or analyzed during the current study are available from the corresponding author on reasonable request.

Foliar spraying of zinc oxide nanoparticles improves water transport and nitrogen metabolism in tomato (Solanum lycopersicum L.) seedlings mitigating the negative impacts of cadmium.

The use of bio-nanotechnology in agriculture-such as the biological applications of metal oxide nanoparticles (NPs)-greatly improves crop yield and quality under different abiotic stress factors including soil metal contamination. Here, we explore the effectiveness of zinc oxide (ZnO)-NPs (0, 50 mg/L) foliar spraying to ameliorate the detrimental effects of cadmium (Cd) on the water transport and nitrogen metabolism in tomato (Solanum lycopersicum Mill. cv. Chibli F1) plants grown on a Cd-supplied (CdCl2; 0, 10, 40 μM) Hoagland nutrient solution. The results depicted that the individually studied factors (ZnO-NPs and Cd) had a significant impact on all the physiological parameters analyzed. Independently to the Cd concentration, ZnO-NPs-sprayed plants showed significantly higher dry weight (DW) in both leaves and roots compared to the non-sprayed ones, which was in consonance with higher and lower levels of Zn2+ and Cd2+ ions, respectively, in these organs. Interestingly, ZnO-NPs spraying improved water status in all Cd-treated plants as evidenced by the increase in root hydraulic conductance (L0), apoplastic water pathway percentage, and leaf and root relative water content (RWC), compared to the non-sprayed plants. This improved water balance was associated with a significant accumulation of osmoprotectant osmolytes, such as proline and soluble sugars in the plant organs, reducing electrolyte leakage (EL), and osmotic potential (ψπ). Also, ZnO-NPs spraying significantly improved NO3- and NH4+ assimilation in the leaf and root tissues of all Cd-treated plants, leading to a reduction in NH4+ toxicity. Our findings point out new insights into how ZnO-NPs affect water transport and nitrogen metabolism in Cd-stressed plants and support their use to improve crop resilience against Cd-contaminated soils.

Effects of root-applied biochar on soil nitrogen transformation and root nitrogen metabolism of cucumber seedlings in facility continuous cropping soils.

The problem of soil barrier caused by excessive accumulation of nitrogen is common in continuous cropping soil of facility agriculture. To investigate the modulating effects of biochar amendment on soil nitrogen transformation in greenhouse continuous cropping systems, we conducted a pot experiment with two treatments, no biochar addition (CK) and 5% biochar addition (mass ratio). We analyzed the effects of biochar addition on soil microbial community structure, abundances of genes functioning in nitrogen cycling, root growth and nitrogen metabolism-related genes expressions of cucumber seedlings. The results showed that biochar addition significantly increased plant height, root dry mass, total root length, root surface area, and root volume of cucumber seedlings. Rhizosphere environment was improved, which enhanced root nitrogen absorption by inducing the up-regulation of genes expressions related to plant nitrogen metabolism. Biochar addition significantly increased soil microbial biomass nitrogen, nitrate nitrogen, and nitrite nitrogen contents. The abundances of bacteria that involved in nitrogen metabolism, including Proteobacteria, Cyanobacteria, and Rhizobiales (soil nitrogen-fixing bacteria), were also significantly improved in the soil. The abundances of genes functioning in soil nitrification and nitrogen assimilation reduction, and the activities of enzymes involved in nitrogen metabolisms such as hydroxylamine dehydrogenase, nitronate monooxygenase, carbonic anhydrase were increased. In summary, biochar addition improved soil physicochemical properties and microbial community, and affected soil nitrogen cycling through promoting nitrification and nitrogen assimilation. Finally, nitrogen adsorption capacity and growth of cucumber plant was increased.

Metabolic alterations in cowpea submitted to water stress

Cowpea is a leguminous plant belonging to the fabaceae family cultivated in the North and Northeast regions of Brazil, with productive potential. Among the abiotic factors, water deficiency is one of the main environmental limitations that influence agricultural production in the world. The objective was to evaluate changes in carbon and nitrogen metabolism in cowpea plants exposed to water deficit. The experiment was conducted in a greenhouse at the Universidade Federal Rural da Amazônia (UFRA, Belém, PA), cowpea plants BR-17 Gurguéia Vigna unguiculata (L.) Walp were used. The experimental design was completely randomized (DIC) in a 2 x 2 factorial scheme, two water conditions (control and water deficit) and two times of stress (four and six days of water suspension), with 7 replications, totaling 28 experimental units. Changes in the metabolism of cowpea plants were evident, with alterations in the activity of the nitrate reductase enzyme, concentrations of total soluble proteins, soluble amino acids, free ammonium and nitrate in the leaf tissue and roots.

Chiral herbicide imazethapy influences plant-soil feedback on nitrogen metabolism by shaping rhizosphere microorganisms.

Herbicides are known to affect the soil nitrogen cycle by shaping soil microorganisms. However, it is not clear how herbicides regulate diverse transformation processes of soil nitrogen cycling by altering rhizosphere microorganisms, subsequently influencing the feedback to plant nitrogen metabolism. Here, we investigated how imazethapyr (IM) enantiomers drive plant-soil feedback on nitrogen metabolism by altering the rhizosphere microorganisms. The results indicated that (R)- and (S)-IM significantly changed the composition and structure rhizosphere microbiome with enantioselectivity and functional changes in microbial communities were associated with soil nitrogen circulation. The determination of nitrogen-cycling functional genes further supported the above findings. The results revealed that (R)- and (S)-IM could change the abundance of nitrogen-cycling functional genes by changing specific bacteria abundances, such as Bacteroidetes, Proteobacteria, and Acidobacteria, thus resulting in diverse nitrogen transformation processes. The alternation of nitrogen transformation processes indicated (R)-IM exhibited a more notable tendency to form a nitrogen cycling pattern with lower energy cost and higher nitrogen retention than (S)-IM. Sterilization experiments demonstrated changes in soil nitrogen cycling drive plant nitrogen metabolism and rhizosphere microorganisms are responsible for the above process of plant-soil feedback for nitrogen metabolism. Under IM enantiomer treatments, rhizosphere microorganisms might stimulate glutamate synthesis by promoting NH4+ uptake and glutamine-glutamate synthesis cycling in roots, thus contributing to positive feedback, with (R)-IM treatments showing more pronounced positive feedback on nitrogen metabolism than (S)-IM treatments. Our results provide theoretical support for determining the mechanism by which IM enantiomers drive plant-soil nitrogen metabolism by changing the rhizosphere microbial communities.

Impact of elevated CO2 concentration on carbon and nitrogen metabolism of irrigated rice plants

Rice is essential to feed the world’s population, being the most important staple food in several countries. Crop production has been directly impacted by climate change. Plants can mitigate an increase in atmospheric CO2 concentration through photosynthetic conversion into carbohydrates. However, the potential for this conversion and plant responses to climate change remain unclear. The study was conducted from the cultivation of plants in open-top chambers (OTCs) with two concentrations of CO2, 400 ppm (ambient – a[CO2]) and 700 ppm (enhanced – e[CO2])). We used rice plants of the cultivar IRGA 424 RI. Evaluations occurred in the vegetative (V5 and V11) and reproductive (R2 and R7) stages. As for gas exchange, plants grown under e[CO2] showed increased net CO2 assimilation rate, greater water use efficiency, and higher intercellular CO2 concentration. On the other hand, the lowest values for stomatal conductance, chlorophyll index, nitrogen balance index, percentage of nitrogen in the leaves, and thousand-grain weight were found for this treatment. In addition, there was an increase in the activity of the glutamine synthetase and nitrate reductase enzymes in leaves and roots under e[CO2], as well as a higher content of nitrate, starch, water-soluble polysaccharides and total soluble sugars in leaves in the first evaluated phenological stage. These results showed us that the reductions in chlorophyll levels added to the stimulation of the photosynthetic machinery elevated the nutritional demand. Due to these impacts, nitrogen and carbon metabolism were reduced, negatively reflecting on the yield components of rice plants.

Root microbiota: Connecting nitrogen metabolism and theanine synthesis in tea plants

Tea varieties exhibit seasonal theanine accumulation, with the high-theanine tea variety Rougui having a diverse root microbiota rich in nitrogen-related microbes. A synthetic community derived from Rougui roots enhances tea growth and theanine synthesis under nitrogen deficiency, emphasizing the microbiota's pivotal role.

Effects of climactic warming on the starch and protein content of winter wheat grain under conservation tillage in the North China Plain

Climate warming is expected to affect global food security and nutritional quality, particularly winter wheat grain protein content. No-tillage (NT) agriculture may be an effective option to mitigate the effects of climate warming; however, the associated mechanism remains unclear. Therefore, this study investigated the effects of warming under NT and conventional tillage (CT) treatments on the physiological growth processes, yield, yield components, plant nitrogen metabolism, as well as grain protein content and fractions of winter wheat in the North China Plain for four consecutive years (2021–2022). The results showed that temperature increases under the NT and CT systems significantly impacted winter wheat growth and development, prolonged the effective reproductive period, and increased the leaf area index, photosynthesis rate, and aboveground dry matter mass in the pre-flowering stage. Hence, the temperature increase and tillage treatment affected the components and yield of winter wheat. The number of fruiting spikelets decreased significantly, and the number of grains and thousand-grain weight increased under the CT and NT systems. Meanwhile, the elevated temperature significantly increased the winter wheat yield by 11.4% (CT) and 62.3% (NT) compared with the control group. Temperature increases also significantly increased winter wheat seed protein content by 10.88% and 30.91% under CT and NT, respectively. The effects of warming and tillage treatments on seed protein fractions were more complex, with warming under CT reducing the albumin, globulin, and glutenin contents, whereas warming under NT increased the contents of all four protein fractions. This study provides a scientific basis for the mechanism underlying climate warming effects on protein content and fractions of winter wheat grains.

Plant Nitrogen Metabolism: Balancing Resilience to Nutritional Stress and Abiotic Challenges

Plant Nitrogen Metabolism: Balancing Resilience to Nutritional Stress and Abiotic Challenges

The mechanism of melatonin promotion on cucumber seedling growth at different nitrogen levels

The supply level of exogenous nitrogen has a very important influence on the growth and development of cucumber. Insufficient or excessive nitrogen application will lead to metabolic disorders in the body and affect the formation of yield. Therefore, it is of great scientific and practical significance to explore the corresponding mitigation measures. Melatonin (MT) is a multi-regulatory molecule with pleiotropic effects on plant growth and development. A large number of studies have shown that the appropriate amount of melatonin supplementation is beneficial to plant growth and development by promoting root development, delaying leaf senescence, and improving fruit yield. However, the study of MT function combined with a detailed physiological analysis of nitrogen (N) absorption and metabolism in cucumber plants needs further strengthening. We performed hydroponic tests at different nitrogen levels to determine the metabolic processes associated with the enhanced tolerance to nitrogen in melatonin-treated cucumber (Cucucumis sativus L.) seedlings. Cucumber seedlings were sprayed with 100 μM melatonin or water and treated with different nitrogen in the growth chamber for 7 days. Nitrogen deficiency significantly inhibited seedling growth, and this growth inhibition was partially alleviated by melatonin. The expression analysis of related carbon and nitrogen genes showed that the genes whose expression was significantly altered by melatonin were mainly related to carbon (C) and nitrogen (N) metabolism. By enzyme activity and reactive oxygen content data analysis, melatonin-treated cucumber seedlings showed relatively stable carbon and nitrogen levels compared to untreated ones. In conclusion, MT can repair the impaired growth and development situation by regulating the nitrogen assimilation capacity and the balance between oxidation and oxidative metabolism and carbon metabolism in the cucumber under different nitrogen levels.

Regulatory effect of graphene on growth and carbon/nitrogen metabolism of maize (Zea mays L.).

Leakage of graphene into the environment has resulted from its increasing use. Although the impact of graphene on ecosystems is already in full swing, information regarding its impact on plants is lacking. In particular, the effects of graphene on plant growth and development vary, and basic information on the regulation of carbon and nitrogen metabolism is missing. In the current study, the way in which graphene (0, 25, 50, 100, and 200 g kg-1 ) affects maize seedlings was studied in terms of morphological and biochemical indicators. The purpose of this study was to understand better how graphene regulates plant carbon and nitrogen metabolism and to understand its interactions with leaf structure and plant growth. The results showed that 50 g kg-1 graphene increased plant height, stem diameter, leaf area, and dry weight; however, this was inhibited by the high level of graphene (200 g kg-1 ). Further studies indicated that different concentrations of graphene could increase leaf thickness and vascular bundle area as well as the net photosynthetic rate (Pn) of leaves; 25 and 50 g kg-1 graphene enhanced the leaves stomatal conductance (Cond), transpiration rate (Tr), intercellular carbon dioxide (Ci), and chlorophyll content. Higher concentrations decreased the above indicators. At 50 g kg-1 , graphene increased the activity of carbon/nitrogen metabolism enzymes by increasing carbon metabolites (fructose, sucrose, and soluble sugars) and soluble proteins (nitrogen metabolites). These enzymes included sucrose synthase (SS), sucrose phosphate synthase (SPS), nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT). These results indicate that graphene can regulate the activities of key enzymes involved in carbon and nitrogen metabolism effectively and supplement nitrogen metabolism through substances produced by carbon metabolism by improving photosynthetic efficiency, thus maintaining the balance between carbon and nitrogen and promoting plant growth and development. The relationship between these indexes explained the mechanism by which graphene supported the growth of maize seedlings by enhancing photosynthetic carbon metabolism and maintaining metabolic balance. For maize seedling growth, graphene treatment with 50 g kg-1 soil is recommended. © 2023 Society of Chemical Industry.

Combinatorial Effects of Glycine and Inorganic Nitrogen on Root Growth and Nitrogen Nutrition in Maize (Zea mays L.)

Organic and inorganic nitrogen play important roles in plant nitrogen nutrition. However, how the coapplication of organic and inorganic nitrogen affects root growth, plant nitrogen metabolism, and soil nitrogen content is still unclear. Plant shoot and root growth, nitrogen uptake and metabolism, and soil nitrogen content were studied in maize (Zea mays L.) through pot experiments with different nitrogen treatments, including NH4+ -N (Amm), NO3− -N (Nit), NH4+ -N + NO3− -N (Amm + Nit), NH4+ -N + NO3− -N + glutamate-N (Amm + Nit + Glu), and NH4+ -N + NO3− -N + glycine-N (Amm + Nit + Gly). The results show that the shoot nitrogen uptake of maize treated with Amm + Nit + Gly was the highest among all the nitrogen treatments. In addition, the coapplication of glycine and inorganic nitrogen increased glutamine synthetase (GS) activity in the maize leaves, promoted nitrogen metabolism levels, and was conducive to the accumulation of amino acids and soluble protein in leaves. Compared with inorganic nitrogen, glycine combined with inorganic nitrogen increased the total root length and root surface area. A correlation analysis showed that total root length and root surface area had a significant positive effect on nitrogen uptake. When ammonium, nitrate, and glycine were applied together, the content of inorganic nitrogen and total nitrogen in soil was higher than that for other inorganic nitrogen treatments. Therefore, we conclude that glycine combined with inorganic nitrogen can increase soil nitrogen content, promote maize root growth, and thus facilitate nitrogen uptake and metabolism.

Asparagine and nitric oxide jointly enhance antioxidant capacity and nitrogen metabolism to improve drought resistance in cotton: Evidence from long‐term field trials

AbstractAsparagine (Asn) and nitric oxide (NO) can enhance plant tolerance to abiotic stress, but their interaction is not well understood. Cotton is a vital resource for the textile industry, but its yield is reduced by drought stress, which could threaten its global supply in a warming and stressful world. Improving cotton's drought tolerance is crucial for supporting the textile industry. Two simultaneous field experiments were conducted to study the effect of Asn and sodium nitroprusside (SNP), a NO donor, on cotton's drought tolerance. Two irrigation treatments were applied: control (C: 100% A pan) and drought stress (50% A pan). The plants were also sprayed with two plant stimulants before imposing drought stress: Mock control, 20 mM Asn, and 0.2 mM SNP, either alone or together. Drought stress impaired plant growth, photosynthesis, yield, nitrogen metabolism, and antioxidant defense, while increasing oxidative stress and free amino acid levels. However, Asn and SNP treatments alleviated these negative effects and improved antioxidant enzyme activity, plant growth, yield, and nitrogen content. The Asn + SNP treatment also increased irrigation water productivity under water‐limited conditions, suggesting its potential for enhancing water use efficiency in cotton production. The combined treatment was more effective than the single treatments, indicating a synergistic effect of Asn and SNP in enhancing drought tolerance in cotton. These results imply that Asn and SNP could be useful tools for sustaining cotton production under drought conditions by boosting nitrogen metabolism and antioxidant defense, thereby contributing to the global supply of cotton and supporting the textile industry.

Uranium affects nitrogen metabolism and endoplasmic reticulum protein homeostasis in plants

The toxicity of uranium (U) to plants makes the phytoremediation effect of U contaminated soil unsatisfactory, and the understanding of the mechanism of U toxicity to plants is limited. In the present study, the effects of U on nitrogen (N) metabolism and endoplasmic reticulum (ER) protein homeostasis in radish (Raphanus sativus) and broad bean (Vicia faba) were analyzed. The results showed that the content of amine N was significantly increased in R. sativus root after U treatment, but significantly decreased in both root and leaf of V. faba, indicating that U had an adverse effect on the N nutrition in V. faba. After U treatment, the nitrate reductase (NR) activity in R. sativus roots and leaves was increased to 2.9 and 4.8 times of that in control group, but decreased by 26.9% and 74.3% in V. faba, respectively. The transcriptome sequencing results showed that 3 NR genes were up-regulated in R. sativus root, while 1 was down-regulated in V. faba after U treatment. In addition, U interfered with ER protein homeostasis and induced ER stress. The bZIP17/28 and bZIP60-mediated unfolded protein response (UPR) pathways were activated in R. sativus root. This promoted downstream ER associated degradation (ERAD) pathway, facilitating the degradation of unfolded (or misfolded) proteins, thereby alleviating ER stress. While in V. faba, U triggered severe programmed cell death through the induction of ER stress, which was significantly alleviated by exogenous addition of the chemical chaperone 4-phenylbutyric acid. Overall, more efficient N assimilation activity and ER protein homeostasis maintenance mechanism (especially ERAD) may be one of the key mechanisms for R. sativus tolerance to U stress. This study for the first time revealed the toxicological mechanism of U in plants in terms of N metabolism and ER protein homeostasis.

Structural and functional studies of Arabidopsis thaliana glutamate dehydrogenase isoform 2 demonstrate enzyme dynamics and identify its calcium binding site

Glutamate dehydrogenase (GDH) is an enzyme at the crossroad of plant nitrogen and carbon metabolism. GDH catalyzes the conversion of 2-oxoglutarate into glutamate (2OG → Glu), utilizing ammonia as cosubstrate and NADH as coenzyme. The GDH reaction is reversible, meaning that the NAD+-dependent reaction (Glu → 2OG) releases ammonia. In Arabidopsis thaliana, three GDH isoforms exist, AtGDH1, AtGDH2, and AtGDH3. The subject of this work is AtGDH2. Previous reports have suggested that enzymes homologous to AtGDH2 contain a calcium-binding EF-hand motif located in the coenzyme binding domain. Here, we show that while AtGDH2 indeed does bind calcium, the binding occurs elsewhere and the region predicted to be the EF-hand motif has a completely different structure. As the true calcium binding site is > 20 Å away from the active site, it seems to play a structural, rather than catalytic role. We also performed comparative kinetic characterization of AtGDH1 and AtGDH2 using spectroscopic methods and isothermal titration calorimetry, to note that the isoenzymes generally exhibit similar behavior, with calcium having only a minor effect. However, the spatial and temporal changes in the gene expression profiles of the three AtGDH genes point to AtGDH2 as the most prevalent isoform.

RNA-Seq analysis of mung bean (Vigna radiata L.) roots shows differential gene expression and predicts regulatory pathways responding to taxonomically different rhizobia

Symbiotic interaction among legume and rhizobia is a complex phenomenon which results in the formation of nitrogen-fixing nodules. Mung bean is promiscuous host however expression profile of this important legume plant in response to rhizobial infection was particularly lacking and urgently needed. We have demonstrated the pattern of gene expression of mung bean roots inoculated with two symbionts Bradyrhizobium yuanmingense Vr50 and Sinorhizobium (Ensifer) aridi Vr33 and non-inoculated control (CK). The RNA-Seq data analyzed at two growth stages i.e., 1–3 h and 10–16 days post inoculation revealed significantly higher number of differentially expressed genes (DEGs) at nodulation stage. The DEGs encoding receptor kinases identified at early stage might be involved in perception of Nod factors produced by different rhizobia. At nodulation stage important genes involved in plant hormone signal transduction, nitrogen and sulfur metabolism were identified. KEGG pathway enrichment analysis showed that metabolic pathways were most prominent in both groups (Group 1: Vr33 vs CK; Group 2: Vr50 vs CK), followed by biosynthesis of secondary metabolites, plant hormone signal transduction and biosynthesis of amino acids. Furthermore, DEGs involved in cell communication and plant hormone signal transduction were found to be different among two symbiotic systems while DEGs involved in carbon, nitrogen and sulfur metabolism were similar but their expression varied in response to two rhizobial strains. This study provides the first insight into the mechanisms underlying interactions of mung bean host with two taxonomically different symbionts (Bradyrhizobium and Sinorhizobium) and the candidate genes for better understanding the mechanisms of symbiotic host-specificity.

Response mechanisms of 3 typical plants nitrogen and phosphorus nutrient cycling to nitrogen deposition in temperate meadow grasslands.

The increase of nitrogen (N) deposition and the diversity of its components lead to significant changes in the structure and function of temperate meadow steppe, which could affect plant nutrient uptake, nutrient resorption and litter decomposition, thus affecting the biogeochemical cycle process. The distribution and metabolism of nitrogen and phosphorus in plants determine the growth process and productivity of plants. Plant nutrient uptake, nutrient resorption and litter decomposition play an important role in the nutrient cycling process of ecosystem. This study closely combined these three processes to carry out experiments with different nitrogen dosages and types, and systematically explored the response of nitrogen and phosphorus nutrient cycling to nitrogen deposition. The results showed that nitrogen deposition can greatly affect ecosystem nutrient cycle of nitrogen and phosphorus. Firstly, Nitrogen deposition has significant effect on plant nutrient uptake. Nitrogen uptake of stems and leaves increased with the increase of nitrogen addition dosage, while phosphorus uptake of stems and leaves showed a downward trend or no significant effect. Besides, nitrogen addition type had a significant effect on nitrogen and phosphorus content of stems. Secondly, Nitrogen addition dosage had a significant effect on plant nutrient resorption, while nitrogen addition type had no significant effect on it. Thirdly, nitrogen deposition has significant effect on litter decomposition. With the increase of nitrogen addition dosage, the initial nitrogen content of litters increased and the decomposition rate of litters accelerated. Nitrogen application type had significant effect on stem litter decomposition. These results indicated that nitrogen deposition significantly affects plant nutrient cycling, and thus affects the structure and function of grassland ecosystem.

Physiological and transcriptional responses of carbohydrate and nitrogen metabolism and ion balance in blueberry plants under nitrogen deficiency

Physiological and transcriptional responses of carbohydrate and nitrogen metabolism and ion balance in blueberry plants under nitrogen deficiency

Reversible Parahydrogen Induced Hyperpolarization of 15 N in Unmodified Amino Acids Unraveled at High Magnetic Field.

Amino acids (AAs) and ammonia are metabolic markers essential for nitrogen metabolism and cell regulation in both plants and humans. NMR provides interesting opportunities to investigate these metabolic pathways, yet lacks sensitivity, especially in case of 15 N. In this study, spin order embedded in p-H2 is used to produce on-demand reversible hyperpolarization in 15 N of pristine alanine and ammonia under ambient protic conditions directly in the NMR spectrometer. This is made possible by designing a mixed-ligand Ir-catalyst, selectively ligating the amino group of AA by exploiting ammonia as a strongly competitive co-ligand and preventing deactivation of Ir by bidentate ligation of AA. The stereoisomerism of the catalyst complexes is determined by hydride fingerprinting using 1 H/D scrambling of the associated N-functional groups on the catalyst (i.e., isotopological fingerprinting), and unravelled by2D-ZQ-NMR. Monitoring the transfer of spin order from p-H2 to 15 N nuclei of ligated and free alanine and ammonia targets using SABRE-INEPT with variable exchange delays pinpoints the monodentate elucidated catalyst complexes to be most SABRE active. Also RF-spin locking (SABRE-SLIC) enables transfer of hyperpolarization to 15 N. The presented high-field approach can be a valuable alternative to SABRE-SHEATH techniques since the obtained catalytic insights (stereochemistry and kinetics) will remain valid at ultra-low magnetic fields.