Glutamine Synthetase Activity Research Articles

A new cyanobacterial species with a protective effect on lettuce grown under salinity stress: Envisaging sustainable agriculture practices

In this work, a new terrestrial cyanobacterial species, Oculatella lusitanica LEGE 161147, was isolated and characterized using a polyphasic approach. Morphologically, O. lusitanica shares characteristics with different Oculatella species (mainly with O. crustae-formantes), lacking distinctive features. However, the phylogeny based on the 16S rRNA gene sequence and the 16S-23S ITS secondary structures support the establishment of this isolate as a new species. O. lusitanica is placed within a clade mainly composed by other Oculatella terrestrial strains; however, it forms a separate lineage. In addition, our species differs from the other Oculatella described so far by lacking the V2 helix within the ITS region. Since cyanobacteria are known to release compounds that promote plant growth and/or increase their tolerance to stresses, the effect of this newly described cyanobacterial species on Lactuca sativa (lettuce) plants development and salinity stress resistance was evaluated. Our results showed that, although the cyanobacterium had no impact on plant growth under the conditions tested, it was able to mitigate the deleterious salinity stress effects on plant size, root and aerial part fresh weight, by eliciting the non-enzymatic antioxidant response system (proline, H2O2 and reduced glutathione). In addition, the microorganism was able to induce a priming effect on lettuce plants by stimulating defensive mechanisms under non-stress conditions, and enhances the activity of nitrogen metabolism-related enzymes glutamate dehydrogenase, glutamine synthetase and nitrate reductase. These results indicate that this native terrestrial cyanobacterial species could be employed as a tool in sustainable agricultural practices.

24-Epibrassinolide and nitric oxide combined to improve the drought tolerance in kiwifruit seedlings by proline pathway and nitrogen metabolism

24-Epibrassinolide (EBR) and nitric oxide (NO) are redox signaling molecules that participate in plant stress response, but their combined role in drought stress response remains unclear. In this study, potted kiwifruit seedlings grown under drought stress were treated with sodium nitroprusside, a NO donor (SNP, 100 μM), 24-epibrassinolide (EBR, 0.01 mg·L−1), and their combination (S+E), as well as well-watered (CK) and drought treatments (DCK). Results revealed that plant biomass, leaf relative water content, photosynthetic pigment content, and photosynthetic capacity of leaves decreased, whereas MDA, H2O2, relative electrolyte leakage, endogenous NO, proline, and soluble sugar content increased in response to drought stress. The application of SNP and EBR alleviated the above adverse effects caused by drought stress and improved the enzyme activities of glutamine synthetase (GS), reduced the glutamate dehydrogenase (GDH) involved in nitrogen metabolism to maintain plant growth, and regulated the expression of aquaporin genes PIP1;1 and PIP2;2–1 to maintain normal water metabolism. The up-regulation of proline synthesis gene P5CR1 expression and the down-regulation of proline degradation gene ProDH expression caused proline accumulation under drought stress. Overall, the combination of SNP and EBR was more effective than independent SNP or EBR in mitigating drought stress in kiwifruit seedlings.

Morphological and Physiological Characteristics of Rice Cultivars with Higher Yield and Nitrogen Use Efficiency at Various Nitrogen Rates

An understanding of the leaf and root traits associated with high nitrogen (N) absorption and utilization is very important in the development of N-efficient varieties in crop breeding programs. However, in rice, the relations between these traits and nitrogen use efficiencies (NUEs) have yet to be identified. Therefore, the responses of leaf and root traits and yields of the three main japonica rice cultivars in northern China were examined at a range of N application rates. The rice cultivars, Shennong 265 (SN265), Tiejing 11 (TJ11), and Fengjing (FJ), were grown in the field at six N rates (0, 60, 120, 180, 240, and 300 kg ha−1) applied during two growing seasons (2018 and 2019). With the increase in N rate, the grain yield of SN265 and TJ11 increased, whereas the grain yield of FJ first increased and then decreased. The grain yield of FJ was higher than that of SN265 and TJ11 at lower N rates, whereas the grain yields of SN265 and TJ11 were higher than that of FJ at higher N rates. The NUEs decreased with the increase in N rates. At lower N rates, the ability of rice to obtain N was the main limitation on rice yield, but with the increase in N rates, the limitation on yield due to N absorption capacity gradually weakened. However, at higher N rates, rice yields were restricted by the ability to utilize N. Compared with TJ11 or FJ, SN265 had higher N utilization capacity primarily because of its higher Rubisco activity, NR activity, GS activity, and ROA. Compared with SN265 or TJ11, FJ had a higher N absorption capacity that was attributed to its larger root architecture, which might have also been one of the reasons for lower N utilization. Therefore, by improving N absorption and utilization-related leaf and root traits, high yields and NUEs can be achieved in rice production at different N application rates.

Increasing Inhibition of the Rat Brain 2-Oxoglutarate Dehydrogenase Decreases Glutathione Redox State, Elevating Anxiety and Perturbing Stress Adaptation.

Specific inhibitors of mitochondrial 2-oxoglutarate dehydrogenase (OGDH) are administered to animals to model the downregulation of the enzyme as observed in neurodegenerative diseases. Comparison of the effects of succinyl phosphonate (SP, 0.02 mmol/kg) and its uncharged precursor, triethyl succinyl phosphonate (TESP, 0.02 and 0.1 mmol/kg) reveals a biphasic response of the rat brain metabolism and physiology to increasing perturbation of OGDH function. At the low (TE)SP dose, glutamate, NAD+, and the activities of dehydrogenases of 2-oxoglutarate and malate increase, followed by their decreases at the high TESP dose. The complementary changes, i.e., an initial decrease followed by growth, are demonstrated by activities of pyruvate dehydrogenase and glutamine synthetase, and levels of oxidized glutathione and citrulline. While most of these indicators return to control levels at the high TESP dose, OGDH activity decreases and oxidized glutathione increases, compared to their control values. The first phase of metabolic perturbations does not cause significant physiological changes, but in the second phase, the ECG parameters and behavior reveal decreased adaptability and increased anxiety. Thus, lower levels of OGDH inhibition are compensated by the rearranged metabolic network, while the increased levels induce a metabolic switch to a lower redox state of the brain, associated with elevated stress of the animals.

Root GS and NADH-GDH Play Important Roles in Enhancing the Ammonium Tolerance in Three Bedding Plants.

Ammonium is a paradoxical nutrient because it is more metabolically efficient than nitrate, but also causes plant stresses in excess, i.e., ammonium toxicity. Current knowledge indicates that ammonium tolerance is species-specific and related to the ammonium assimilation enzyme activities. However, the mechanisms underlying the ammonium tolerance in bedding plants remain to be elucidated. The study described herein explores the primary traits contributing to the ammonium tolerance in three bedding plants. Three NH4+:NO3− ratios (0:100, 50:50, 100:0) were supplied to salvia, petunia, and ageratum. We determined that they possessed distinct ammonium tolerances: salvia and petunia were, respectively, extremely sensitive and moderately sensitive to high NH4+ concentrations, whereas ageratum was tolerant to NH4+, as characterized by the responses of the shoot and root growth, photosynthetic capacity, and nitrogen (amino acid and soluble protein)-carbohydrate (starch) distributions. An analysis of the major nitrogen assimilation enzymes showed that the root GS (glutamine synthetase) and NADH-GDH (glutamate dehydrogenase) activities in ageratum exhibited a dose-response relationship (reinforced by 25.24% and 6.64%, respectively) as the NH4+ level was raised from 50% to 100%; but both enzyme activities were significantly diminished in salvia. Besides, negligible changes of GS activities monitored in leaves revealed that only the root GS and NADH-GDH underpin the ammonium tolerances of the three bedding plants.

Eliciators increase gas exchanges and induce the Zea mays antioxidant system

The plant elicitors use as an agricultural input is limited and few studies show their influence on physiological responses. However, its use can induce broad-spectrum and long-lasting resistance in plants by inducing defense systems, primary and secondary metabolism. The the aim of this study was to evaluate the gas exchange (gs, A, E, Ci, WUE, iWUE and iCE) and enzymatic antioxidant system (POD, PPO and PAL) of Z. mays under elicitors application. The experiment was carried out in a completely randomized design with seven treatments: control (sterilized distilled water); Rocksil® (3 g L-1); Poagrim® (3 g L-1); Bion® (0.4 g L-1); Agrosilicon Plus® (3 g L-1); Ecolife® (3 mL L-1); Thiabendazol® (1 g L-1), with four repetitions and three plants per repetition. Gas exchange (net photosynthesis [A], stomatal conductance [gs], internal carbon concentration [Ci], transpiration rate [E], instantaneous water use efficiency [WUE= A/E], intrinsic water use efficiency [iWUE= A/gs], instantaneous carboxylation efficiency [iCE= A/Ci], and enzymatic activity (peroxidase [POX], polyphenol oxidase [PPO], phenylalanine ammonia-lyase [PAL]) were evaluated at 40 and 45 days after sowing. Gs, A, WUE, iCE and peroxidase activity increased in plants whose seeds were soaked with Rocksil® and Thiabendazol®. The phenylalanine ammonia-lyase activity was reduced in plants from seeds soaked in Ecolife®. The elicitors increased the gas exchange and antioxidant system of Zea mays L.

Effects of oxytetracycline and zinc ion on nutrient removal and biomass production via microalgal culturing in anaerobic digester effluent

Removal of nutrients from swine wastewater digester effluent (SWDE) by microalgae Coelastrella sp. and production of Coelastrella sp. were investigated at the presence of oxytetracycline (OTC) and Zn(II). Mechanisms of stress of OTC and Zn(II) on microalgae were discussed via analyzing the removal performance of SWDE and biochemical characteristics of microalgae. Results showed that removal efficiency of ammonia nitrogen and biomass yield of microalgae at the presence of 5000 μg/L of OTC decreased by 13.1% − 50.1% and 28.2% −71.5%, respectively, when Zn concentration was increased from 0.50 mg/L to 5.0 mg/L. The presence of 5.0 mg/L Zn(II) promoted the accumulation of lipids in microalgae, and the presence of 50 μg/L OTC increased unsaturation of fatty acid methyl ester. Content of glutathione and activity of both glutamine synthetase and superoxide dismutase decreased with the increase of OTC concentration, while content of adenosine triphosphatase increased when Zn(II) concentration was also increased.

Dep1 improves rice grain yield and nitrogen use efficiency simultaneously by enhancing nitrogen and dry matter translocation

The rice cultivars carrying dep1 (denseanderectpanicle1) have the potential to achieve both high grain yield and high nitrogen use efficiency (NUE). However, few studies have focused on the agronomic and physiological performance of those cultivars associated with high yield and high NUE under field conditions. Therefore, we evaluated the yield performance and NUE of two near-isogenic lines (NILs) carrying DEP1 (NIL-DEP1) and dep1-1 (NIL-dep1) genes under the Nanjing 6 background at 0 and 120 kg N ha−1. Grain yield and NUE for grain production (NUEg) were 25.5 and 21.9% higher in NIL-dep1 compared to NIL-DEP1 averaged across N treatments and planting years, respectively. The yield advantage of NIL-dep1 over NIL-DEP1 was mainly due to larger sink size (i.e., higher total spikelet number), grain-filling percentage, total dry matter production, and harvest index. N utilization rather than N uptake contributed to the high yield of NIL-dep1. Significantly higher NUEg in NIL-dep1 was associated with higher N and dry matter translocation efficiency, lower leaf and stem N concentration at maturity, and higher glutamine synthetase (GS) activity in leaves. In conclusion, dep1 improved grain yield and NUE by increasing N and dry matter transport due to higher leaf GS activity under field conditions during the grain-filling period.

Identification of Glutamine Synthetase as a Contryphan-Bt Binding Protein by His-Tag Pull-Down.

Contryphan-Bt is a D-tryptophan-containing disulfide-constrained decapeptide recently isolated from the venom of Conus betulinus. The molecular targets of contryphans are controversial, and the identification of its interacting proteins may be of great importance. His-tag pull-down assays were performed to investigate intracellular binding proteins of contryphan-Bt from rat brain lysate. Bt-Acp-[His]6, a contryphan-Bt derivative containing hexahistidine tag, was synthesized and used as the bait. As a control, Acp-[His]6 was used to exclude nonspecific bindings. Glutamine synthetase was identified as a potential contryphan-Bt binding protein by pull-- down assays and subsequent LC-MS/MS. The binding of contryphan-Bt to glutamine synthetase was confirmed and determined using microscale thermophoresis, with a Kd of 74.02 ± 2.8 μM. The binding did not affect glutamine synthetase activity, suggesting that the interaction site was distinct from the catalytic center. Glutamine synthetase was identified as a novel contryphan-Bt binding protein. This is the first report in which the conopeptide binds to an intracellular protein.

Characterization of glutamine synthetase from the ammonium-excreting strain HM053 of Azospirillum brasilense.

Glutamine synthetase (GS), encoded by glnA, catalyzes the conversion of L-glutamate and ammonium to L-glutamine. This ATP hydrolysis driven process is the main nitrogen assimilation pathway in the nitrogen-fixing bacterium Azospirillum brasilense. The A. brasilense strain HM053 has poor GS activity and leaks ammonium into the medium under nitrogen fixing conditions. In this work, the glnA genes of the wild type and HM053 strains were cloned into pET28a, sequenced and overexpressed in E. coli. The GS enzyme was purified by affinity chromatography and characterized. The GS of HM053 strain carries a P347L substitution, which results in low enzyme activity and rendered the enzyme insensitive to adenylylation by the adenilyltransferase GlnE.

The combined supplementation of melatonin and salicylic acid effectively detoxifies arsenic toxicity by modulating phytochelatins and nitrogen metabolism in pepper plants

The main objective of the study was to assess if joint application of melatonin (MT, 0.1 mM) and salicylic acid (SA 0.5 mM) could improve tolerance of pepper plants to arsenic (As) as sodium hydrogen arsenate heptahydrate (0.05 mM). The imposition of arsenic stress led to accumulation of As in roots and leaves, and increased contents of leaf proline, phytochelatins, malondialdehyde (MDA) and H2O2, but it reduced plant biomass, chlorophylls (Chl), PSII maximum efficiency (Fv/Fm) and leaf water potential. Melatonin and SA applied jointly or alone enhanced nitrogen metabolism by triggering the activities of glutamate synthase, glutamine synthetase, and nitrite reductases and nitrate. In comparison with a single treatment of MT or SA, the joint treatment of MT and SA had better impact on enhancing growth and key biological events and decreasing tissue As content. This clearly shows a cooperative function of both agents in enhancing tolerance to As-toxicity in pepper plants.

Impact of Sprouting under Potassium Nitrate Priming on Nitrogen Assimilation and Bioactivity of Three Medicago Species.

Edible sprouts are rich in flavonoids and other polyphenols, as well as proteins, minerals, and vitamins. Increasing sprout consumption necessitates improving their quality, palatability, and bioactivity. The purpose of this study was to test how KNO3 priming affects the sprouting process species on three Medicago species (Medicago indicus, Medicago interexta, and Medicago polymorpha) and their nutritional values. Targeted species of Medicago were primed with KNO3, and the levels of different primary and secondary metabolites were determined. KNO3 induced biomass accumulation in the sprouts of the three species, accompanied by an increased content of total mineral nutrients, pigments, vitamins, and essential amino acids. Besides, our results showed that KNO3 enhanced the activity of nitrate reductase (NR), glutamate dehydrogenase (GDH), and glutamine synthetase (GS) enzymes, which are involved in the nitrogen metabolism and GOGAT cycle, which, in turn, increase the nitrogen and protein production. KNO3 treatment improved the bioactive compound activities of Medicago sprouts by increasing total phenolic and flavonoid contents and enhancing the antioxidant and antidiabetic activities. Furthermore, species-specific responses toward KNO3 priming were noticeable, where Medicago interexta showed the highest antioxidant and antidiabetic activities, followed by Medicago polymorpha. Overall, this study sheds the light on the physiological and biochemical bases of growth, metabolism, and tissue quality improvement impact of KNO3 on Medicago sprouts.

The role of grip strength and short physical performance battery test in predicting chemotherapy-related outcomes in older adults with cancer

BackgroundGrip strength (GS) and the Short Physical Performance Battery (SPPB) are brief objective tests used during a comprehensive geriatric assessment (CGA) to assess physical performance. Abnormal GS and SPPB scores are associated with greater morbidity and mortality in older adults with cancer but their relationship with chemotherapy tolerability is unclear. We explored the performance of GS and SPPB in predicting therapy delay, dose reduction, and treatment completion in older adults undergoing chemotherapy or chemoradiation. Additionally, we examined associations between GS, SPPB, and instrumental activities of daily living (IADLs). MethodsRetrospective review of patients ≥65 years old who had undergone a pre-treatment CGA in a geriatric oncology clinic were retrieved from electronic charts and institutional databases. Abnormal GS was defined as <26 kg and < 16 kg for men and women, respectively. Abnormal SPPB was defined as ≤9 points. Logistic regression was used to examine the associations between abnormal GS or SPPB alone or combined with chemotherapy-related outcomes (e.g., delay, dose reduction, completion). Chi-squared tests were used to determine associations between physical performance measures (GS and SPPB) and IADLs. ResultsA total of 85 participants (mean age 79.1 years old) with mixed cancer diagnoses were included. Approximately 67% of participants exhibited abnormal GS or SPPB prior to treatment. Abnormal GS or SPPB (combined) was associated with treatment delay (odds ratio (OR) = 7.58, 95% confidence interval (CI) = 1.77, 32.43, P = 0.006). When physical performance measures were examined separately, only SPPB predicted treatment delay (OR = 3.26, 95%CI = 1.04, 10.21, P = 0.043). Abnormal GS or SPPB were not associated with dose reduction or treatment completion. Abnormal GS and SPPB alone or combined demonstrated only modest sensitivity (41.9–76.7%) and negative predictive value (57.9–64.2%) in identifying IADLs dependence. ConclusionGS and SPPB may be used to predict treatment delay in older adults prior to chemotherapy and chemoradiation. Additional studies are warranted to examine whether GS and/or SPPB can predict dose reduction and treatment completion in older adults prior to receiving chemotherapy or chemoradiation.

Growth, Quality, and Nitrogen Assimilation in Response to High Ammonium or Nitrate Supply in Cabbage (Brassica campestris L.) and Lettuce (Lactuca sativa L.)

Plants grow better when they are supplied with a combination of ammonium (NH4+) and nitrate (NO3−) than when either one is supplied as the sole N (nitrogen) source. However, the effects of N forms on N metabolism and major N assimilation enzymes in different plants, especially vegetables, are largely neglected. This study was conducted on two plants with distinct NH4+ tolerances to compare the responses of two popular leafy vegetables, Korean cabbage (Brassica campestris L.) ‘Ssamchu’ and lettuce (Lactuca sativa L.) ‘Caesar green’, to the N source. To this end, plant growth and quality, photosynthesis, carbohydrate, N contents (in the forms of NO3−, NO2−, NH4+, total protein), and key N assimilation-related enzyme (NR, NIR, GS, GDH) activities were investigated. When plants were subjected to one of three NH4+:NO3− regimes, 0:100, 50:50, or 100:0, lettuce was relatively more tolerant while cabbage was extremely sensitive to high NH4+. Both plants benefited more from being grown with 50:50 NH4+:NO3−, as evidenced by the best growth performance, ameliorated photosynthesis, and enriched carbohydrate (C) stock content. In addition, as compared to cabbage, the GS and GDH activities were reinforced in lettuce in response to an increasing external NH4+ level, resulting in low NH4+ accumulation. Our findings suggested that boosting or maintaining high GS and GDH activities is an important strategy for the ammonium tolerance in vegetables.

Assembly status transition offers an avenue for activity modulation of a supramolecular enzyme.

Nature has evolved many supramolecular proteins assembled in certain, sometimes even seemingly oversophisticated, morphological manners. The rationale behind such evolutionary efforts is often poorly understood. Here, we provide atomic-resolution insights into how the dynamic building of a structurally complex enzyme with higher order symmetry offers amenability to intricate regulation. We have established the functional coupling between enzymatic activity and protein morphological states of glutamine synthetase (GS), an old multi-subunit enzyme essential for cellular nitrogen metabolism. Cryo-EM structure determination of GS in both the catalytically active and inactive assembly states allows us to reveal an unanticipated self-assembly-induced disorder-order transition paradigm, in which the remote interactions between two subcomplex entities significantly rigidify the otherwise structurally fluctuating active sites, thereby regulating activity. We further show in vivo evidences that how the enzyme morphology transitions could be modulated by cellular factors on demand. Collectively, our data present an example of how assembly status transition offers an avenue for activity modulation, and sharpens our mechanistic understanding of the complex functional and regulatory properties of supramolecular enzymes.

Interspecies interaction for nitrogen use efficiency via up-regulated glutamine and glutamate synthase under wheat-faba bean intercropping

• Intercropping drove higher grain N and total N accumulation, NTE, and NUE. • Interspecies interaction upregulated GS/GOGAT activity and gene expression in leaves. • GS/GOGAT stimulated by intercropping linked with higher straw and total N accumulation. • Upregulated GS/GOGAT after wheat heading stages contributed to higher NTE and NUE. Glutamine synthetase (GS) and the glutamate synthase (GOGAT) cycle are closely related to plant nitrogen (N) uptake, translocation, and remobilization, but little attention has been paid to their role in intercropping systems. A two-factor field trial involving two planting patterns (mono-cropped wheat [MW] and wheat intercropped with faba bean) and four N levels (N0, N1, N2, and N3 with respective application rates of 0, 90, 180, and 270 kg ha −1 for wheat) were studied. Nitrogen accumulation and allocation were determined, and the GS and GOGAT activities and their gene expression in the leaves were analyzed. The results showed that wheat total aboveground N accumulation and grain N accumulation were increased when wheat was intercropped with faba bean. Intercropped wheat (IW) presented higher N translocation efficiency (NTE) than MW (except for the N3 level during 2018–2019) during the reproductive growth stage. Thus, the grain yield (except for the N3 level), N harvest index (NHI), and apparent N recovery rate (ANR) were higher in IW than in MW. In addition, total GS, Fd-GOGAT, and NADH-GOGAT activities in the wheat leaves were increased by 27 %–42 %, 17 %–44 %, and 15 %–25 %, respectively, under the N0, N1, and N2 levels from the stem elongation to filling stages when wheat was intercropped with faba bean. On average, GS1, GS2, Fd-GOGAT, and NADH-GOGAT gene expression in the IW flag leaves was 1.4–4.3 times, 1.2–3.6 times, 1.2–2.2 times, and 1.4–6.7 times higher, respectively, than that in MW. Both GS and GOGAT activity and gene expression were tightly related to straw N accumulation and NTE rather than grain N accumulation based on simple correlation analysis. In addition, wheat total N accumulation at maturity was more sensitive to GS and GOGAT activity and gene expression in the flag leaves during the heading, flowering, and filling stages, and ANR only linked with GS and GOGAT activity at the filling stage. Hence, it could be concluded that up-regulated GS and GOGAT activity and gene expression induced by intercropping during the reproductive growth stages contributed to higher NTE and NUE in intercropping. These findings suggest that interspecies interactions modulated GS and GOGAT, which play a crucial role in the intercropping advantage and provide insight into the mechanism of enhanced NUE under intercropping.

Physiological and Transcriptomic Responses to Nitrogen Deficiency in Neolamarckia cadamba.

Nitrogen (N) is one of the abundant and essential elements for plant growth and development, and N deficiency (ND) affects plants at both physiological and transcriptomic levels. Neolamarckia cadamba is a fast-growing woody plant from the Rubiaceae family. However, the physiological and molecular impacts of ND on this species have not been well investigated. Here, we studied how N. cadamba responds to ND under hydroponic conditions. In a physiological aspect, ND led to a reduction in biomass, chlorophyll content, and photosynthetic capacity. ND also impaired the assimilation of N as the activities of glutamine synthetase (GS) and nitrate reductase (NR) were decreased in the root. Interestingly, the lignin content of stem increased progressively during the ND stress. The main transcription factors, the transcription factors that are important to N regulation has been found to be upregulated, including Nodule inception-like protein 7 (NLP7), TGACG motif-binding factor 1 (TGA1), basic helix-loop-helix protein 45 (BHLH45), NAM, ATAF1,2, CUC2 (NAC) transcription factor 43 (NAC43), and basic leucine zipper pattern 44 (bZIP44). The expression of N transporters, such as nitrate transporter 2.4 (NRT2.4), ammonium transporter 3 (AMT3), and amino acid transporter protein 3 (AAP3), was also upregulated. In addition, phosphorus- and calcium-related genes such as phosphate starvation response 2 (PHR2) and cyclic nucleotide-gated ion channel 15 (CNGC15) were expressed more abundantly in response to ND stress. Our results reveal the physiological and molecular mechanisms by which woody plants respond to ND.

Nitrogen management under increased atmospheric CO2 concentration in cucumber (Cucumis sativus L.): ameliorating environmental impacts of fertilization

In the last years, the atmospheric CO2 concentration has increased significantly, and this increase can cause changes in various physiological and biochemical processes of plants. However, the response of plants to elevated CO2 concentration (e[CO2]) will be different depending on the nitrogen form available and the plant species. Therefore, hydroponic trials on cucumber plants, with two CO2 concentrations (400 and 1000 ppm) and two nitrogen sources (NO3−/NH4+; 100/0 and 90/10), were conducted. Physiological parameters—such as gas exchange, GS, GOGAT and GDH activities, cation composition, soluble sugar and starch content- were measured. The results showed that when plants were grown with NH4+ and e[CO2], parameters such as photosynthesis rate (ACO2), instantaneous water use efficiency (WUEi), the content of NH4+, Ca2+ and Mg2+, and the concentration of starch, were higher than in control plants (irrigated with nitrate as sole nitrogen source and ambient CO2 concentration (a[CO2])). Furthermore, an improvement in N assimilation was observed when the GS/GOGAT pathway was enhanced under these conditions (NH4+ and e[CO2]). Thus, our results contribute to the reduction of the negative environmental impacts of the use of nitrogen fertilizers on this crop, both by reducing nitrogen leakage (eutrophication) and greenhouse gas emissions.

Effects of sowing modes on soil water dynamics and grain protein formation in dryland wheat.

In order to clarify the mechanisms underlying dryland wheat quality improvement through sowing technology, the effects of wide space sowing (WSS), furrow sowing (FS), and drill sowing (DS) on soil moisture dynamics and grain protein formation in dryland wheat field were studied in Wenxi, Shanxi Province in 2017-2018 (normal year) and 2018-2019 (dry year). The results showed that compared with the DS, FS significantly increased soil water storage in the 0-200 cm depth at anthesis stage (8.2%-18.7%), and increased the soil water storage in 0-60 cm layer during the two years, 60-120 cm layer in normal year, and 120-200 cm layer in dry year. WSS significantly increased soil water storage in 0-200 cm layer at anthesis stage in normal year (5.2%). Compared with DS, FS significantly increased water consumption of anthesis to mature stage, while WSS significantly increased water consumption from sowing to anthesis stage in dry year. Compared with DS, the glutamine synthetase (GS) activity of grains at 15-35 days after anthesis was significantly increased by FS and WSS, while the glutamate synthase (GOGAT) activity of flag leaves and grains at 5-35 days after anthesis was significantly increased by FS in the dry year. Compared with DS, FS significantly increased grain yield by 20.4%-44.8%, grain protein yield by 25%-49%, and increased grain albumin and globulin contents. WSS significantly increased grain yield by 9%-40%, and increased grain gliadin content. Under different sowing modes of dryland wheat, GS and GOGAT activities in flag leaves and grains after anthesis were significantly correlated with water consumption at anthesis to maturity stage. There were significant correlations between GS and GOGAT activities in flag leaves and grains and 0-120 cm soil layers in the normal water year, and between GS and GOGAT activities and 0-60 cm, 120-200 cm soil layers in the dry year. The contents of grain albumin, globulin and total protein were significantly correlated with soil water storage in 0-60 cm layer at anthesis stage, as well as soil water storage in 120-200 cm layer at anthesis stage in the dry year. In conclusion, FS was beneficial to increasing soil water storage at anthesis and water consumption after anthesis of dryland wheat, improving GS and GOGAT activities of flag leaf and grain, with positive consequences on yield and grain protein content. In addition, deep water storage was more conducive to quality improvement in the late growth period in the dry year.

Increased glutamine synthetase by overexpression of TaGS1 improves grain yield and nitrogen use efficiency in rice

Improving nitrogen use efficiency (NUE) has been a focal point for crop growth and yield throughout the world. Glutamine synthetase (GS), which plays a fundamental role in N metabolism, has been exploited to improve crop NUE. However, increased GS activity in rice by overexpressing its own GS genes hasn't shown superior plant productivity. Here, transgenic rice plants with increased GS activity by overexpressing TaGS1 were analyzed under field and culture conditions at two N rates. Transgenic expression of TaGS1 significantly increases GS activity in leaves, junctions and roots of rice plants relative to wide-type plants. When rice plants grown under consecutive field trials with N rates of 60 and 240 kg/ha, three transgenic lines have higher grain yield than wild-type plants, with increment of 15%–22% in T2 generation and with that of 28%–36% in T3 generation, respectively. And increased panicle numbers (effective tiller numbers) mainly contribute to the advantage of grain yield in transgenic plants. Analysis of N use-related traits shows that transgenic plants with enhanced GS activity promote root capacity to obtain N, N accumulation during growth stages and N remobilization to grains, ultimately conferring 31%–40% improvement of NUE relative to wild-type rice plants.