Glutamine Synthetase Activity Research Articles

Improved physiological and morphological traits of root synergistically enhanced salinity tolerance in rice under appropriate nitrogen application rate.

Numerous papers studied the relations between nitrogen rate and rice yield in saline soils, whereas the rice root morphological and physiological characteristics mediating nitrogen rates in yield formation under varied salinity levels remain less concerns. Through a field experiment applied with five nitrogen rates (0, 210, 255, 300, 345, and 390 kg ha–1) in saline land, we found that rice yield peaked at 7.7 t ha–1 under 300 kg ha–1 nitrogen, and excessive N was not conductive for increasing yield. To further elucidate its internal physiological mechanism, a pot experiment was designed with three N rates (210 [N1], 300 [N2], 390 [N3] kg ha–1) and three salt concentrations (0 [S0], 1.5 [S1], 3.0 [S2] g kg–1 NaCl). Results showed that the average grain yield was decreased by 19.1 and 51.1% under S1 and S2, respectively, while notably increased by 18.5 and 14.5% under N2 and N3, respectively. Salinity stress significantly inhibited root biomass, root length and surface area, root oxidation capacity (ROC), K+ and K+/Na+ ratio, and nitrogen metabolism-related enzyme activities, whereas root Na+ and antioxidant enzyme activities were notably increased. The mechanism of how insufficient N supply (N1) affected rice yield formation was consistent at different salinity levels, which displayed adverse impacts on root morphological and physiological traits, thereby significantly inhibiting leaf photosynthesis and grain yield of rice. However, the mechanism thorough which excessive N (N3) affected yield formation was quite different under varied salinity levels. Under lower salinity (S0 and S1), no significant differences on root morphological traits and grain yield were observed except the significantly decline in activities of NR and GS between N3 and N2 treatments. Under higher salinity level (S2), the decreased ROC, K+/Na+ ratio due to increased Na+, antioxidant enzyme activities, and NR and GS activities were the main reason leading to undesirable root morphological traits and leaf photosynthesis, which further triggered decreased grain yield under N3 treatment, compared to that under N2 treatment. Overall, our results suggest that improved physiological and morphological traits of root synergistically enhanced salinity tolerance in rice under appropriate nitrogen application rate.

Sugarcane Genotypes with Contrasting Biological Nitrogen Fixation Efficiencies Differentially Modulate Nitrogen Metabolism, Auxin Signaling, and Microorganism Perception Pathways.

Sugarcane is an economically important crop that is used for the production of fuel ethanol. Diazotrophic bacteria have been isolated from sugarcane tissues, without causing visible plant anatomical changes or disease symptoms. These bacteria can be beneficial to the plant by promoting root growth and an increase in plant yield. Different rates of Biological Nitrogen Fixation (BNF) were observed in different genotypes. The aim of this work was to conduct a comprehensive molecular and physiological analysis of two model genotypes for contrasting BNF efficiency in order to unravel plant genes that are differentially regulated during a natural association with diazotrophic bacteria. A next-generation sequencing of RNA samples from the genotypes SP70-1143 (high-BNF) and Chunee (low-BNF) was performed. A differential transcriptome analysis showed that several pathways were differentially regulated among the two BNF-contrasting genotypes, including nitrogen metabolism, hormone regulation and bacteria recognition. Physiological analyses, such as nitrogenase and GS activity quantification, bacterial colonization, auxin response and root architecture evaluation, supported the transcriptome expression analyses. The differences observed between the genotypes may explain, at least in part, the differences in BNF contributions. Some of the identified genes might be involved in key regulatory processes for a beneficial association and could be further used as tools for obtaining more efficient BNF genotypes.

Chronic heat stress causes liver damage via endoplasmic reticulum stress-induced apoptosis in broilers

Liver is a central metabolic organ, which is sensitive to heat stress. Liver damage affects animals' health and endangers the livestock and poultry industry. This study aimed to investigate the mechanism of chronic heat stress-induced liver damage in broiler chickens. Broilers were divided into 3 treatments: normal control group (NOR, 22°C), heat stress group (HS, 32°C) and pair-feeding group (PF, 22°C) for a 7-d and 14-d trial. The results showed that 7 d heat exposure caused microvesicular steatosis and reduced glutamine synthetase activity in broiler liver (P < 0.05). After 14 d of heat exposure, heat stress caused vacuolar degeneration and apoptosis in the liver; elevated liver relative weight and liver glutaminase activity as well as plasma ammonia level (P < 0.05). Additionally, heat stress enhanced GRP78 protein expression and the mRNA expressions of endoplasmic reticulum (ER) stress responses genes and apoptosis-related genes in broiler liver after 14 d of heat exposure (P < 0.05). In conclusion, chronic heat stress triggered ER stress-induced apoptosis and caused liver damage, which may compromise ammonia detoxification in broiler liver.

Metabolic changes of the reduction of manganese intake in the hepatic encephalopathy rat: NMR- and MS-based metabolomics study.

To investigate the metabolic changes in type C hepatic encephalopathy (CHE) rats after reducing manganese (Mn) intake. A total of 80 Sprague-Dawley rats were divided into control group and CHE groups (induced by intraperitoneal injection of thioacetamide at a dose of 250mg/kg of body weight twice a week for 6 weeks). CHE rats were subdivided into 1Mn group (fed a standard diet, with 10mg Mn/kg feed), 0.5Mn group (half-Mn diet), 0.25Mn group (quarter-Mn diet) and 0Mn group (no-Mn diet) for 4 to 8weeks. Morris water maze (MWM), Y maze and narrow beam test (NBT) were used to evaluate cognitive and motor functions. Blood ammonia, brain Mn content, the number of GS-positive cells, and glutamine synthetase (GS) activity were measured. The metabolic changes of CHE rats were investigated using hydrogen-nuclear magnetic resonance and mass spectrometry. Multivariate statistical analysis was used to analyze the results. Significantly decreased numbers of entries in target area of MWM and Y maze, longer NBT latency and total time, higher blood ammonia, brain Mn content and GS activity were found in CHE rats. After reducing Mn intake, CHE rats had better behavioral performance, significantly lower blood ammonia, brain Mn content and GS activity. The main up-regulated metabolites were Ala, GABA, Glu, Gln, Lac, Tyr, Phe in 1Mn rats. After reducing Mn intake, metabolites returned to normal level at different degrees. Reducing Mn intake could reduce brain Mn content and blood ammonia, regulate GS activity and amino acid metabolism, ultimately improve behavioral performance in CHE rats.

Selection and functional identification of Dof genes expressed in response to nitrogen in Populus simonii × Populus nigra.

In plants, Dof transcription factors are involved in regulating the expression of a series of genes related to N uptake and utilization. Therefore, the present study investigated how DNA-binding with one finger (Dof) genes are expressed in response to nitrogen (N) form and concentration to clarify the role of Dof genes and their functions in promoting N assimilation and utilization in poplar. The basic characteristics and expression patterns of Dof genes in poplar were analyzed by the use of bioinformatics methods. Dof genes expressed in response to N were screened, after which the related genes were cloned and transformed into Arabidopsis thaliana; the physiological indexes and the expression of related genes were subsequently determined. The function of Dof genes was then verified in Arabidopsis thaliana plants grown in the presence of different N forms and concentrations. Forty-four Dof genes were identified, most of which were expressed in the roots and young leaves, and some of the Dof genes were expressed under ammonia- and nitrate-N treatments. Three genes related to N induction were cloned, their proteins were found to localize in the nucleus, and PnDof30 was successfully transformed into Arabidopsis thaliana for functional verification. On comparing Arabidopsis thaliana with WT Arabidopsis thaliana plants, Arabidopsis thaliana plants overexpressing the Dof gene grew better under low N levels; the contents of soluble proteins and chlorophyll significantly increased, while the soluble sugar content significantly decreased. The expressions of several AMT, NRT, and GS genes were upregulated, while the expressions of several others were downregulated, and the expression of PEPC and PK genes significantly increased. In addition, the activity of PEPC, PK, GS, and NR enzymes significantly increased. The results showed that overexpression of PnDof30 significantly increased the level of carbon and N metabolism and improved the growth of transgenic Arabidopsis thaliana plants under low-N conditions. The study revealed the biological significance of poplar Dof transcription factors in N response and regulation of related downstream gene expression and provided some meaningful clues to explain the huge difference between poplar and Arabidopsis thaliana transformed by exogenous Dof gene, which could promote the comprehensive understanding of the molecular mechanism of efficient N uptake and utilization in trees.

Regulation effects of carbonized apple branches on absorption, distribution, and utilization of 15N single-labeled ammonium nitrate (15NH4NO3 or NH415NO3) in Malus hupehensis

To improve the utilization of nitrogen fertilizer and orchard waste, the apple branches were separated and pyrolyzed into carbonized wood and carbonized bark, and then applied to root-zone soil of potted Malus hupehensis. The physiological characteristics of leaves and roots were detected, and the absorption, utilization, and distribution of 15NH4NO3 and NH415NO3 in plants were analyzed using the 15N isotope tracer technique. The results indicated that the net photosynthetic rate and water use efficiency of leaves, the root growth, and the activity of nitrate reductase and glutamine synthetase were greatest increased by 1.0% (w:w) carbonized bark and carbonized wood, and the effect of carbonized bark was more effective. The carbonized bark more effectively increased nitrogen derived from fertilizer (Ndff) value in all organs, the distribution of 15N in roots, and utilization of the 15NH4NO3 and NH415NO3 of Malus hupehensis compared with carbonized wood at the same application ratio, and 1.0% ratio performed better than other ratios in these terms. The Malus hupehensis treated with carbonized bark had the highest utilization ratio of 15NH4NO3 (10.54%) when the application ratio was 1.0%, and the corresponding parameter of NH415NO3 was 12.98%. The soil immobilization capacity of 15N was improved, and carbonized bark resulted in the greatest decrease in the loss ratios of 15NH4NO3 and NH415NO3 under 1.0% ratio, which decreased by 27.33% and 30.08%, respectively. For reducing nitrogen loss and improving nitrogen utilization, carbonized bark was more effective than carbonized wood, mainly because bark contained more cellulose and less lignin than wood.

Competitive success of the invasive species, Hydrilla verticillata, over Vallisneria neotropicalis in nature could be linked to differences in nitrogen metabolism

Invasive species are considered the second most important threat to biodiversity, only behind habitat loss across all ecosystems. Although much of the work characterizing the competitive success of invasive species has identified life-history traits such as vigorous vegetative growth, long flowering times, and substantial seed yields, that are common to invaders, research has not clearly elucidated mechanisms driving invasion in all plant species. Hence, the objective of this work was to examine invasive and native submerged aquatic plants at the molecular, biochemical, and physiological levels to identify metabolic processes that mechanistically promote the competitive success of invasive species. This was done by studying nitrate uptake and assimilation in two submerged aquatic plant species, Hydrilla verticillata (L.F.) and Vallisneria neotropicalis (Marie-Vict.). Examination of nitrate uptake, nitrate reductase activity, glutamine synthetase activity, and expression of nitrate uptake and assimilation-related genes indicate that H. verticillata has a higher capacity to take up and assimilate nitrate than does V. neotropicalis throughout the growing season. From this work, it can be concluded that the invasive species, H. verticillata, has a superior competitive strategy through the majority of the growing season that relies on rapid uptake and assimilation of nitrate.

Environmental nitrogen and phosphorus nutrient variability triggers intracellular resource reallocation in Gracilariopsis lemaneiformis (Rhodophyta)

The variability in anthropogenic input of nutrients to coastal water has profound impacts on the ecology of Gracilariopsis lemaneiformis, a rhodophyte that is protein-rich and economically valuable for food and industry. However, little is known about how this alga responds to the dynamics of nitrogen and phosphorus (NP) nutrients. In this study, G. lemaneiformis was grown in batch cultures under three nutrient regimes (low-, medium- and high-NP abundances, with a constant N:P ratio of 10) to investigate the physiological, biochemical and transcriptional responses to the variation in N and P nutrient abundances. Under high-NP treatment conditions, G. lemaneiformis exhibited a high growth rate and contents of phycoerythrin, Chl a and soluble protein, but lower contents of soluble sugar and activities of nitrate reductase and glutamine synthetase. Besides, we found a negative correlation between the soluble sugar and soluble protein (R2 = 0.86), suggesting reallocation of intracellular resources modulated by extracellular NP nutrients. Furthermore, the carbon content decreased under high-NP conditions, indicating G. lemaneiformis biomass accumulation at the expense of per unit weight carbon content. In addition, we found that arginine was the main storage form of N in G. lemaneiformis, and its content increased 1017 times in a two-week period under N- and P- enriched conditions. Moreover, the phycoerythrin was the main biologically active N-compound used by G. lemaneiformis for growth, compared to soluble protein and Chl a, under N- and P-deficient conditions. These findings demonstrate that even under constant stoichiometry, the environmental variability of nutrient abundance shapes biochemical landscapes in the algal cell and provides baseline information to help design G. lemaneiformis cultivation to obtain higher protein or higher soluble sugar with respect to NP nutrition.

Nitrogen and Chemical Control Management Improve Yield and Quality in High-Density Planting of Maize by Promoting Root-Bleeding Sap and Nutrient Absorption.

High-density planting aggravates competition among plants and has a negative impact on plant growth and productivity. Nitrogen application and chemical control can improve plant growth and increase grain yield in high-density planting. Our experiment explored the effects of nitrogen fertilizer and plant growth regulators on maize root-bleeding sap, phosphorus (P) and potassium (K) accumulation and translocation, and grain yield and quality in high-density planting. We established a field study during the 2017 and 2018 growing seasons, with three nitrogen levels of N100 (100 kg ha−1), N200 (200 kg ha−1), and N300 (300 kg ha−1) at high-density planting (90,000 plants ha−1), and applied Yuhuangjin (a plant growth regulator mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf. Our results showed that N200 application combined with chemical control could regulate amino acid and mineral nutrient concentration delivery rates in root-bleeding sap and improve its sap rate. Also, the treated plant exhibited higher P and K uptake and translocation ability. Furthermore, chemical control and N200 treatment maintained a high level of ribulose-1,5-bisphosphate carboxylase (RuBPCase), phosphoenolpyruvate carboxylase (PEPCase), nitrate reductase (NR), and glutamine synthetase (GS) enzymatic activities in leaves. In addition, plant growth regulator and nitrogen application improved the enzymatic activities of GS, glutamate dehydrogenase (GDH), and glutamic pyruvic transaminase (GPT) and the contents of crude protein, lysine, sucrose, and soluble sugar in grain and ultimately increased maize yield. This study suggests that N200 application in combination with chemical control promotes root vitality and nutrient accumulation and could improve grain yield and quality in high-density planting.

Administration of Phosphonate Inhibitors of Dehydrogenases of 2-Oxoglutarate and 2-Oxoadipate to Rats Elicits Target-Specific Metabolic and Physiological Responses.

In vitro and in cell cultures, succinyl phosphonate (SP) and adipoyl phosphonate (AP) selectively target dehydrogenases of 2-oxoglutarate (OGDH, encoded by OGDH/OGDHL) and 2-oxoadipate (OADH, encoded by DHTKD1), respectively. To assess the selectivity in animals, the effects of SP, AP, and their membrane-penetrating triethyl esters (TESP and TEAP) on the rat brain metabolism and animal physiology are compared. Opposite effects of the OGDH and OADH inhibitors on activities of OGDH, malate dehydrogenase, glutamine synthetase, and levels of glutamate, lysine, citrulline, and carnosine are shown to result in distinct physiological responses. ECG is changed by AP/TEAP, whereas anxiety is increased by SP/TESP. The potential role of the ester moiety in the uncharged precursors of the 2-oxo acid dehydrogenase inhibitors is estimated. TMAP is shown to be less efficient than TEAP, in agreement with lower lipophilicity of TMAP vs. TEAP. Non-monotonous metabolic and physiological impacts of increasing OADH inhibition are revealed. Compared to the non-treated animals, strong inhibition of OADH decreases levels of tryptophan and beta-aminoisobutyrate and activities of malate dehydrogenase and pyruvate dehydrogenase, increasing the R–R interval of ECG. Thus, both metabolic and physiological actions of the OADH-directed inhibitors AP/TEAP are different from those of the OGDH-directed inhibitors SP/TESP, with the ethyl ester being more efficient than methyl ester.

Magnetic Treatment Improves the Seedling Growth, Nitrogen Metabolism, and Mineral Nutrient Contents in Populus × euramericana ‘Neva’ under Cadmium Stress

This pot experiment was carried out to investigate the mechanism underlying nutrient metabolism and seedling growth responses to magnetic treatment following exposure to cadmium (Cd) stress. A magnetic device of 300 Gs was applied during Cd(NO3)2 solution treatment at 0 and 100 mM·L−1. One-year-old seedlings of Populus × euramericana ‘Neva’ were treated with different Cd(NO3)2 solutions in the presence or absence of magnetic treatment for 30 days. Seedling growth and physiological–biochemical indexes were measured under Cd stress. The contents of ammonium (NH4+–N), nitrate (NO3––N), and total nitrogen (TN) in leaves, as well as NH4+–N and TN in roots, were increased by magnetic treatment combined with Cd stress, although the NO3––N content was decreased. The activities of nitrate reductase (NR), nitrite reductase (NiR), glutathione reductase (GR), and glutamate synthase (GOGAT) in leaves and the activities of NR, glutamine synthetase (GS), and GOGAT in roots were stimulated by magnetic treatment; conversely, the NiR activity in roots was inhibited by magnetic effects. Magnetic treatment improved the synthesis of cysteine (Cys) and glutamine (Gln) in leaves and reduced the contents of glutamic acid (Glu) and glycine (Gly), while the contents of Cys, Glu, Gln, and Gly were increased in roots. The contents of Ca, Mg, Fe, Mn, Zn, and Cu in leaves were increased by magnetic treatment under Cd stress, whereas the content of K was reduced. In roots, the contents of K, Ca, and Fe were increased by magnetic treatment under Cd stress, but the contents of Na, Mg, Mn, Zn, and Cu were decreased. Magnetization could regulate the uptake of mineral nutrients by roots and translocation from the roots to the aboveground parts by affecting root morphology. Magnetic treatment could also improve nitrogen assimilation and the synthesis of free amino acids by stimulating the activities of key enzymes.

Leaf Scorching following Foliar Fertilization of Wheat with Urea or Urea–Ammonium Nitrate Is Caused by Ammonium Toxicity

Foliar fertilization is a potential tool to increase the use-efficiency of nitrogen (N) fertilizers. However, whilst leaf scorching has frequently been reported, the underlying physiological processes are not clear. In the present work, we investigate the intensity of leaf scorching as affected by the balance between ammonium assimilation and accumulation. Leaves were sprayed with urea–ammonium nitrate (UAN) solution without surfactant or applied liquid droplets of urea in different N concentrations with surfactant. UAN solutions without surfactant containing &gt;10% N caused leaf scorching already after 24 h and the severity increased with the N concentration. The same pattern was observed 3 days after the application of urea solutions containing &gt;4% N together with surfactant. The scorching was accompanied by a massive increase in foliar and apoplastic ammonium (NH4+) concentration. Moreover, the activity of glutamine synthetase (GS), most pronouncedly that of the chloroplastic isoform (GS2), decreased a few hours after the application of high N-concentrations. Along with this, the concentration of glutamate—the substrate for GS—decreased. We conclude that leaf scorching is promoted by NH4+ accumulation due to a limitation in N assimilation capacity.

The Involvement of Antioxidant Enzyme System, Nitrogen Metabolism and Osmoregulatory Substances in Alleviating Salt Stress in Inbred Maize Lines and Hormone Regulation Mechanisms.

Salt stress inhibited the growth of maize. B46 and NC236 were chosen as materials and NaCl concentrations (0, 55, 110, 165, and 220 mmol L−1) were set. We found the activities of SOD, POD, CAT, APX, GR, MDHAR, and DHAR decreased under NaCl stress. Compared with NC236, the contents of AsA and GSH, AsA/DHA and GSH/GSSG of B46 decreased. The content of O2−, H2O2, MDA, and EL of B46 increased. The contents of NO3− and NO2− decreased, while the content of NH4+ increased under high NaCl concentration. The activities of NR and NiR decreased, while the activities of GS and GOGAT increased first and then decreased. For B46 and NC236, the maximum of NADH-GDH and NAD-GDH appeared at 165 and 110 mmol L−1 NaCl concentration, respectively. Compared with B46, and the GOT and GPT activities of NC236 increased first and then decreased. With the increase of NaCl concentration, the contents of proline, soluble protein, and soluble sugar were increased. The Na+ content of B46 and NC236 increased, and the K+ content and K+/Na+ decreased. Compared with NC236, B46 had higher IAA content in leaf, higher Z + ZR content in leaf and root, and lower ABA content in leaf and root.

Rice varieties with contrasting nitrogen use efficiency present different expression of amino acid transporters and ammonium transporters

ABSTRACT We evaluated the effects of isoforms of ammonium transporters (AMT) and amino acid transporters (AAT) on three rice varieties cultivated with different levels of ammonium (NH4 +) and its biochemical responses. The rice varieties used were IAC-47 (improved), Manteiga and Piauí (landraces), cultivated under 0.2 mM NH4 + (low N, LN), 1 mM NH4 + (sufficient N, SN) or resupply with 1 mM of NH4 + after three days without nitrogen (N). When cultivated with LN, the Piauí variety presented a higher expression of AAT (Lysine-Histidine Transporter 4 (OsLHT4) and GABA Transporters (OsGAT1)) in roots, while Manteiga and IAC-47 presented higher expression of the Amino Acid Permease 1 (OsAAP1) and Ammonium Transporter 1.1 (OsAMT1.1), respectively. Additionally, Piauí had the higher expression of glutamine synthetase (OsGS1.1 and OsGS1.3) in shoots cultivated with LN or resupply. The Piauí variety displayed higher glutamine synthetase activity and amino acid content under resupply. Manteiga and Piauí presented a lower reduction in fresh weight of leaves and sheaths under LN compared to IAC-47. The results suggest that the improved variety IAC-47 is more efficient when cultivated with SN, while, under LN or resupply, the landrace varieties were superior. Overall, the molecular responses were different among the varieties, which may affected their nitrogen metabolism.

Foxtail millet [Setaria italica (L.) Beauv.] over-accumulates ammonium under low nitrogen supply

Nitrogen (N) deficiency is a primary limiting factor for crop production worldwide. Previously, we reported root system architectural modifications of hydroponically cultured foxtail millet [Setaria italica (L.) Beauv.] to facilitate N translocation under N limitation. Here, we investigated foxtail millet for its shoot adaptation to low N in terms of internal N regulation under hydroponic culture. The results of this study revealed that the shoot N and nitrate (NO3−) concentrations significantly declined as compared to control (CK); however, the shoot over-accumulated ammonium (NH4+) under low N (LN). N shortage resulted in down-regulation of expressions of SiPetA, SiccsA, SipsbA, SirpoB, SipsaA, SiatpA, Sirps16, and SiPEPC which, undermined chloroplast functioning and CO2 assimilation for the provision of carbon skeleton. Carbon deficiency and lower activities of GS decelerated ammonia assimilation and led to over-accumulation of NH4+ in the LN-shoot, as indicated by lower concentrations of total amino acids. Thus, enhanced GOGAT activity was to assimilate NH4+ while, those of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) were to scavenge reactive oxygen species (ROS) of NH4+ toxicity framework. The weakened chloroplast factory eventually minimized photosynthesis and reduced dry mass of the LN shoot. Such regulation of N by the shoot, perhaps, resurrected physiological functions which maintained internal mineral status under nitrogen limitation in foxtail millet.

Nickel Toxicity Interferes with NO3-/NH4+ Uptake and Nitrogen Metabolic Enzyme Activity in Rice (Oryza sativa L.).

The excessive use of nickel (Ni) in manufacturing and various industries has made Ni a serious pollutant in the past few decades. As a micronutrient, Ni is crucial for plant growth at low concentrations, but at higher concentrations, it can hamper growth. We evaluated the effects of Ni concentrations on nitrate (NO3−) and ammonium (NH4+) concentrations, and nitrogen metabolism enzyme activity in rice seedlings grown in hydroponic systems, using different Ni concentrations. A Ni concentration of 200 μM significantly decreased the NO3− concentration in rice leaves, as well as the activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthetase (GOGAT), respectively, when compared to the control. By contrast, the NH4+ concentration and glutamate dehydrogenase (GDH) activity both increased markedly by 48% and 46%, respectively, compared with the control. Furthermore, the activity of most active aminotransferases, including glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT), was inhibited by 48% and 36%, respectively, in comparison with the control. The results indicate that Ni toxicity causes the enzymes involved in N assimilation to desynchronize, ultimately negatively impacting the overall plant growth.

Genetic Diversity in Nitrogen Fertiliser Responses and N Gas Emission in Modern Wheat.

Crops assimilate nitrogen (N) as ammonium via the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway which is of central importance for N uptake and potentially represents a bottle neck for N fertiliser-use efficiency. The aim of this study was to assess whether genetic diversity for N-assimilation capacity exists in wheat and could be exploited for breeding. Wheat plants rapidly, within 6 h, responded to N application with an increase in GS activity. This was not accompanied by an increase in GS gene transcript abundance and a comparison of GS1 and GS2 protein models revealed a high degree of sequence conservation. N responsiveness amongst ten wheat varieties was assessed by measuring GS enzyme activity, leaf tissue ammonium, and by a leaf-disc assay as a proxy for apoplastic ammonia. Based on these data, a high-GS group showing an overall positive response to N could be distinguished from an inefficient, low-GS group. Subsequent gas emission measurements confirmed plant ammonia emission in response to N application and also revealed emission of N2O when N was provided as nitrate, which is in agreement with our current understanding that N2O is a by-product of nitrate reduction. Taken together, the data suggest that there is scope for improving N assimilation capacity in wheat and that further investigations into the regulation and role of GS-GOGAT in NH3 emission is justified. Likewise, emission of the climate gas N2O needs to be reduced, and future research should focus on assessing the nitrate reductase pathway in wheat and explore fertiliser management options.

The effects of fullerene on photosynthetic apparatus, chloroplast-encoded gene expression, and nitrogen assimilation in Zea mays under cobalt stress.

Carbon nanostructures, such as the water-soluble fullerene (FLN) derivatives, are considered perspective agents for agriculture. FLN can be a novel nano-agent modulating plant response against stress conditions. However, the mechanism underlying the impacts of FLN on plants in agroecosystems remains unclear. Zea mays was exposed to exogenous C60 -FLN applications (FLN1: 100; FLN2: 250; and FLN3: 500 mg L-1 ) with/without cobalt stress (Co, 300 μM) for 3 days (d). In the maize chloroplasts, Co stress disrupted the photosynthetic efficiency and the expression of genes related to the photosystems (psaA and psbA). FLNs effectively improved the efficiency and photochemical reaction of photosystems. Co stress induced the accumulation of reactive oxygen species (ROS) as confirmed by ROS-specific fluorescence in guard cells. Co stress increased only chloroplastic superoxide dismutase (SOD) and peroxidase (POX). Stress triggered oxidative damages in maize chloroplasts, measured as an increase in TBARS content. In Co-stressed seedlings exposed to FLN1 and FLN2 exposures, the hydrogen peroxide (H2 O2 ) was scavenged through the nonenzymes/enzymes-related to the AsA-GSH cycle by preserving ascorbate (AsA) conversion, as well as GSH/GSSG and glutathione (GSH) redox state. Also, the alleviation effect of FLN3 against stress could be attributed to increased glutathione S-transferase (GST) activity and AsA regeneration. FLN applications reversed the inhibitory effects of Co stress on nitrogen assimilation. In maize chloroplasts, FLN increased the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), nitrite reductase (NiR), and glutamine synthetase (GS), which provided conversion of inorganic nitrogen (N) into organic N. The ammonium (NH4 + ) toxicity was removed via GS and GDH but not glutamate synthase (GOGAT). The increased NAD-GDH (deaminating) and NADH-GDH (aminating) activities indicated that GDH was needed more for NH4 + detoxification. Therefore, FLN exposure to Co-stressed maize plants might play a role in N metabolism regarding the partitioning of N assimilates. Exogenous FLN conceivably removed Co toxicity by improving the expressions of genes related to reaction center proteins of photosystems, increasing the level of enzymes related to the defense system, and improving the N assimilation in maize chloroplasts.

Pre-anthesis night warming improves post-anthesis physiological activity and plant productivity to post-anthesis heat stress in winter wheat (Triticum aestivum L.)

Global warming is asymmetric, with the increase in temperature at night being greater than that during the day. In this study, we conducted night warming treatments using a passive heating device on the wheat variety ‘Yangmai 18′ grown in culture pots in an experimental field. The night warming treatments were performed from the tillering stage to the jointing stage (NW T-J ), from the jointing stage to the booting stage (NW J-B ), and from the booting stage to the anthesis stage (NW B-A ). A non-warming treatment was used as a control (NN). Post-anthesis heat (H) stress was performed during the grain-filling stage. The results showed that treatments NW T-J and NW J-B significantly enhanced grain yield by increasing the 1000-grain weight, while the NW J-B treatment showed the highest impact. Night warming treatments at early growth stages significantly prevented the grain-yield reduction caused by heat stress during grain filling. NW J-B treatment increased the sucrose content and sucrose phosphate synthase (SPS) activity of the flag leaves under heat stress during grain filling, which increased the ability of the plants to convert post-anthesis photoassimilates into sucrose, providing a basis for the accumulation of sucrose in the grains. Meanwhile, NW J-B treatment increased the ability of the plants to assimilate and utilize nitrogen by increasing the nitrogen content and activity of nitrate reductase (NR) and glutamine synthetase (GS) of the flag leaves under heat stress during grain filling. Post-anthesis assimilation products and the activities of the enzymes related to carbon and nitrogen metabolism in wheat plants subjected to night warming treatments maintained at a higher level, which promoted the formation and conversion of proteins and starches in the grains at the late growth stages. Night warming treatments from the jointing to booting stage effectively improved post-anthesis physiological activity and plant productivity, which reduced yield loss caused by heat stress during grain filling. • Night warming priming at early growth stages increased the photosynthetic assimilation capacity of the wheat. • Night warming priming at early growth stages also increased the ability of wheat to accumulate and transfer nitrogen under heat stress during grain filling. • Night warming priming from the jointing to booting stage showed the highest impact.

Cyanobacterial inoculation in elevated CO2 environment stimulates soil C enrichment and plant growth of tomato

The present study investigated the influence of cyanobacterial inoculants viz., Anabaena laxa (A.laxa) ), Calothrix elenkinii (C. elenkinii) and Anabaena torulosa- Trichoderma viride (An-Tr) under ambient (aCO2) and elevated (eCO2) conditions, on soil and plant parameters, when grown with/without tomato crop. Significant enhancement in soil chlorophyll, proteins, polysaccharide content, total leaf pigments and C-N assimilating enzyme activities was recorded under elevated CO2 conditions with cyanobacterial inoculation, when grown with/without tomato crop. Supplementation with A. laxa led to more than a fold-enhancement in polysaccharides and 40%–45% increment in available nitrogen, while An-Tr recorded 60%–70% increase in soil microbial biomass carbon under elevated CO2 condition. A. laxa treatment also recorded highest plant pigments, glutamine synthetase and carbonic anhydrase activity under elevated CO2 condition. Distinct influence of elevated CO2 condition, cyanobacterial inoculation and plant and their interactions were recorded. Interestingly, plants grown under elevated CO2 showed early flowering, by eight days, compared to ambient conditions. Phospholipid fatty acid profiles of soil samples illustrated significant changes in the total biomass and distribution of notional microbial groups due to inoculation and the presence of plant. Multivariate analyses illustrated the significant interactions among the soil and microbiological attributes, highlighting that cyanobacterial inoculation can be a promising intervention to utilize beneficially the elevated CO2 for enhancing soil nutrients, crop growth and productivity in tomato.