Enzymes Of Nitrogen Metabolism Research Articles

Elucidation of the role of glutamine synthetase seed isoform GLN1;5 in Arabidopsis thaliana (L.) with a reverse genetics approach

Glutamine synthetase (E.C. 6.3.1.2) is a key enzyme of plant nitrogen metabolism that assimilates ammonia into glutamine. The Arabidopsis thaliana genome encodes one chloroplastic (GLN2) and five cytosolic (GLN1;1 ? GLN1;5) isoforms with different expression patterns, kinetic properties, regulation and functions. Physiological roles of different isoforms have been elucidated mainly by studying knockout mutants. However, the role of GLN1;5, which is expressed in dry seeds, remains unknown. To clarifty the function of GLN1;5, we studied a GLN1;5 knockout line (GLN1;5KO) homozygous for T-DNA insertion within the GLN1;5. GLN1;5 deficiency results in a phenotype with slightly delayed bolting and fewer siliques. The dry weight of GLN1;5KO seeds was 73.3% of wild-type (WT) seed weight, with seed length 90.9% of WT seeds. Finally, only 18.33% of the mutant seeds germinated in water within 10 days in comparison to 34.67% of WT seeds. KNO3 strongly stimulated germination of both GLN1;5KO and WT seeds, while germination in the presence of increasing NH4Cl concentrations potentiated the differences between the two genotypes. It can be concluded that GLN1;5 activity supports silique development and grain filling and that it has a role in ammonium reassimilation in the seed, as well as assimilation and/or detoxification of ammonium from the environment. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON173024 and Grant no. ON173015]

Knockout of SlSBPASE Suppresses Carbon Assimilation and Alters Nitrogen Metabolism in Tomato Plants.

Sedoheptulose-1,7-bisphosphatase (SBPase) is an enzyme in the Calvin–Benson cycle and has been documented to be important in carbon assimilation, growth and stress tolerance in plants. However, information on the impact of SBPase on carbon assimilation and nitrogen metabolism in tomato plants (Solanum lycopersicum) is rather limited. In the present study, we investigated the role of SBPase in carbon assimilation and nitrogen metabolism in tomato plants by knocking out SBPase gene SlSBPASE using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing technology. Compared with wild-type plants, slsbpase mutant plants displayed severe growth retardation. Further analyses showed that knockout of SlSBPASE led to a substantial reduction in SBPase activity and as a consequence, ribulose-1,5-bisphosphate (RuBP) regeneration and carbon assimilation rate were dramatically inhibited in slsbpase mutant plants. It was further observed that much lower levels of sucrose and starch were accumulated in slsbpase mutant plants than their wild-type counterparts during the photoperiod. Intriguingly, mutation in SlSBPASE altered nitrogen metabolism as demonstrated by changes in levels of protein and amino acids and activities of nitrogen metabolic enzymes. Collectively, our data suggest that SlSBPASE is required for optimal growth, carbon assimilation and nitrogen metabolism in tomato plants.

Effect of Epichloë gansuensis endophyte on the activity of enzymes of nitrogen metabolism, nitrogen use efficiency and photosynthetic ability of Achnatherum inebrians under various NaCl concentrations

This study explored the effects of Epichloe gansuensis endophyte on photosynthetic ability, the activity of nitrogen metabolism enzymes, nitrogen use efficiency, and biomass accumulation of Achnatherum inebrians growing under five NaCl concentrations. A. inebrians plants with (E+) and without E. gansuensis (E−) were grown under different NaCl concentrations. Photosynthetic indexes, NO3− and NH4+ content, nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) activity, nitrogen use efficiency and nitrogen content were determined. The plant total biomass, NO3− and N content, NR, NiR and GS activity, total N accumulation (TNA), nitrogen utilization efficiency (NUtE) and nitrogen uptake efficiency (NUpE) were higher in leaves and roots of E+ than of E− plants under 300 and 400 mM NaCl concentrations, but NH4+ content was lower in leaves and roots of E+ than of E− plants under 100, 200, 300 and 400 mM NaCl concentrations. However, there were almost no significant effects on these factors between E+ and E− plants under the 0 mM NaCl concentration. The endophyte improved the growth of plants under high NaCl concentration by improving photosynthetic ability, increasing the activity of nitrogen metabolism enzymes and nitrogen use efficiency.

Effect Of Sodium Nitro-Prusside( Snp) Pretreatment on Ammonia Assimilating Enzymes of Salt Stressed Tomato Leaves (Lycopersicon esculentum)

THE EFFECTS of treatment with 100mM NaCl on photosynthetic activity, protein and proline contents , activities of key nitrogen metabolism enzymes, nitrate reductase (NR) and nitrite reductase (NiR), ammonia assimilating enzymes: Glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (NADH-GDH) activities and finally ammonia and nitrate contents were investigated in 40-day old leaves of tomato plants. There was a decline in total protein (TP) and insoluble protein (InsP) fractions accompanied with a significant increase in proline and soluble protein contents in response to NaCl – stress. Under salinized conditions, there was a significant inhibition in all tested leaf gas exchange parameters, stomatal conductance (gs), internal CO2 concentration (Ci) and hence, CO2 assimilation (A). Also, a significant inhibition of NR & NiR enzymes and a strongly decrease in nitrate content were observed. In contrast, ammonia assimilating enzymes (GS, GOGAT, NADH-GDH and NAD-GDH) activities were obviously increased in NaCl – salinized tomato leaves, this accompanied with a significant increase in ammonia content. Soaking tomato seeds in 10μM sodium nitroprusside (SNP) for 8h were elevated-to some extent- all the studied parameters and there was an improvement in TP, proline, all gas exchange parameters, NR & NiR activities and nitrate content. While ammonia assimilating enzymes (GS, GOGAT, NADH-GDH and NAD-GDH) activities and ammonia content were significantly decreased compared to NaCl - salinized tomato leaves.

Genomic and Proteomic Analyses of Salmonella enterica Serovar Enteritidis Identifying Mechanisms of Induced de novo Tolerance to Ceftiofur.

With the alarming proliferation of antibiotic resistance, it is important to understand the de novo development of bacterial adaptation to antibiotics in formerly susceptible lineages, in the absence of external genetic input from existing resistance pools. A strain of ceftiofur susceptible Salmonella enterica serovar Enteritidis ABB07-SB3071 (MIC = 1.0 μg/ml) was successively exposed to sub-MIC of ceftiofur to allow its adaptation for tolerance to a concentration of 2.0 μg/ml of this antibiotic. Genomic and proteomic comparative analyses of the parental strain and induced tolerant derived lineages were performed to characterize underlying mechanisms of de novo adaptation (tolerance). Expression and localization of specific drug-, heme-, sugar-, amino acid-, and sulfate-transporters were altered, as was the localization of the cell membrane stabilizing protein OsmY in the tolerant strains adapted to 2.0 μg/ml compared to the parental isolate lines. This redistribution of existing transporters acts to minimize the concentrations of ceftiofur in the periplasm, by decreasing facilitated import and increasing active efflux and cytosolic sequestration as determined by high performance liquid chromatography quantification of residual total and extracellular ceftiofur after growth. Genetic, subcellular localization, and abundance changes of specific regulators of transcription, translation, and post-translational dynamics in the derived ceftiofur tolerant lineages decrease metabolic strain on cell walls and enhance periplasmic envelop stability against stress. This produces slower growing, more tolerant populations, which deplete free ceftiofur concentrations significantly more than susceptible parental populations (P < 0.05), as measured by recoverable levels of ceftiofur from cultures of equivalent cellular density incubated with equal ceftiofur concentrations. Genetic and abundance changes to specific carbon and nitrogen metabolism enzymes, not traditionally associated with beta-lactam metabolism, establish an enzymatic framework with the potential to detoxify/degrade ceftiofur, while mutations and changes in subcellular localization in specific cell surface factors enhance the stability of the Gram-negative cell envelop despite the compromising effect of ceftiofur. The observed changes highlight generalizable mechanisms of de novo tolerance without horizontal gene transfer, and thus can inform policies to combat antibiotic tolerance and minimize induction of de novo tolerance.

Activities of Carbon and Nitrogen Metabolism Enzymes of Sorghum (Sorghum bicolor L. Moench) During Seed Development

Carbon and nitrogen metabolism pathways are regulated by complex mechanisms in order to optimize growth and development of plants and play a major role in determining the amount of protein stored in cereal grains. This study was conducted to contribute to determine the roles of certain key enzymes of carbon and nitrogen metabolism in developing sorghum seeds. Sorghum bicolor (L.) Moench was grown in a growth chamber. Seeds were harvested at various stages of development and used to the analysis of certain key enzymes of carbon and nitrogen metabolism. The results were subjected to stastistical analysis using one-way analysis of variance (ANOVA) followed by the Tukey test. The results showed that during the seed development the highest activities of glutamine synthetase, glutamate dehydrogenase, phosphoenolpyruvate carboxylase, malate dehydrogenase, isocitrate dehydrogenase, and aspartate aminotransferase were detected at the time of maximum seed filling stages (15-20 DAP). Hence, higher activities of these enzymes at the time of maximum seed-filling stages could be effectively linked to amino acids synthesis and therefore the deposition of protein reserves.

Boron: Functions and Approaches to Enhance Its Availability in Plants for Sustainable Agriculture.

Boron (B) is an essential trace element required for the physiological functioning of higher plants. B deficiency is considered as a nutritional disorder that adversely affects the metabolism and growth of plants. B is involved in the structural and functional integrity of the cell wall and membranes, ion fluxes (H+, K+, PO43−, Rb+, Ca2+) across the membranes, cell division and elongation, nitrogen and carbohydrate metabolism, sugar transport, cytoskeletal proteins, and plasmalemma-bound enzymes, nucleic acid, indoleacetic acid, polyamines, ascorbic acid, and phenol metabolism and transport. This review critically examines the functions of B in plants, deficiency symptoms, and the mechanism of B uptake and transport under limited B conditions. B deficiency can be mitigated by inorganic fertilizer supplementation, but the deleterious impact of frequent fertilizer application disrupts soil fertility and creates environmental pollution. Considering this, we have summarized the available information regarding alternative approaches, such as root structural modification, grafting, application of biostimulators (mycorrhizal fungi (MF) and rhizobacteria), and nanotechnology, that can be effectively utilized for B acquisition, leading to resource conservation. Additionally, we have discussed several new aspects, such as the combination of grafting or MF with nanotechnology, combined inoculation of arbuscular MF and rhizobacteria, melatonin application, and the use of natural and synthetic chelators, that possibly play a role in B uptake and translocation under B stress conditions.

Analysis of Nitrogen Utilization Capability during the Proliferation and Maturation Phases of Norway Spruce (Picea abies (L.) H.Karst.) Somatic Embryogenesis

Somatic embryogenesis (SE) is a laboratory-based method that allows for cost-effective production of large numbers of clonal copies of plants, of particular interest for conifers where other clonal propagation methods are mostly unavailable. In this study, the effect of l-glutamine as an organic nitrogen source was evaluated for three contrasted media (containing NH4 + NO3 without glutamine, or glutamine + NO3, or glutamine without inorganic nitrogen) during proliferation and maturation of Norway spruce somatic embryos through analyses of activities of the key enzymes of nitrogen metabolism: nitrate reductase (NR), glutamine synthetase (GS) and arginase. A major change in nitrogen metabolism was indicated by the increased activity of GS from zero in the proliferation stage through maturation to high activity in somatic embryo-derived plantlets; furthermore, NR activity increased from zero at the proliferation stage to high activity in maturing embryos and somatic-embryo derived plantlets. In contrast, arginase activity was high at all stages. In accordance with the GS and NR data, proliferation was fastest on the glutamine media, the largest number of mature embryos developed on the glutamine medium without inorganic nitrogen, and the ammonium content of proliferating cultures was much higher than that of mature somatic embryos. The best developed embryos, judged by germination, were from the glutamine + NO3 medium. These insights into nitrogen utilization will help to improve culture medium composition.

Effect of Epichloë gansuensis Endophyte on the Nitrogen Metabolism, Nitrogen Use Efficiency, and Stoichiometry of Achnatherum inebrians under Nitrogen Limitation.

The systemic fungal endophyte of the grass Achnatherum inebrians, Epichloë gansuensis, has important roles in enhancing resistance to biotic and abiotic stresses. In this work, we first evaluated the effects of E. gansuensis on nitrogen metabolism, nitrogen use efficiency, and stoichiometry of A. inebrians under varying nitrogen concentrations. The results demonstrated that E. gansuensis significantly improved the growth of A. inebrians under low nitrogen conditions. The fresh and dry weights, nitrogen reductase, nitrite reductase, and glutamine synthetase activity, NO3-, NH4+, N, and P content, and also the total N accumulation, N utilization efficiency, and N uptake efficiency were all higher in leaves of A. inebrians with E. ganusensis (E+) plants than A. inebrians plants without this endophyte (E-) under low nitrogen availability. In conclusion, E. gansuensis has positive effects on improving the growth of A. inebrians under low-nitrogen conditions by modulating the enzymes of nitrogen metabolism and enhancing nitrogen use efficiency.

Mechanism exploration on nitrogen metabolism and secondary metabolism in Atropa belladonna hairy roots treated with yeast extract

In order to study the mechanism of nitrogen metabolism and secondary metabolism in Atropa belladonna hairy roots treated with yeast extract, yeast extract（YE） was added to the culture medium. Then the changes of physiological and biochemical indexes of A. belladonna hairy roots after treatment with YE were detected. The results are as follows，the activity of key enzymes of nitrogen metabolism changed differently. Compared with the control group (CK), the activity of nitrate reductase (NR) and glutamine synthetase (GS) were significantly increased, while the activity of glutamate dehydrogenase (GDH) was not changed significantly. The content of nitrate nitrogen, ammonium nitrogen had a significant decrease,but the content of soluble protein, free amino acid, total nitrogen are significantly more than CK. Moreover, YE treatment led to the increase of the content precursor amino acids (ornithine and arginine) and precursor putrescine in secondary metabolic pathways of A. belladonna. The expression level of gene putrescine N-methyl transferase (pmt), tropinone reductase-I (trI) and hyoscyamine 6-β-hydroxylase(h6h) all increased in a different rate caused by YE treatment, which eventually led to the increase of the yield of tropane alkaloids. The yield of hyoscyamine and scopolamine were 3.09 and 1.85 folds than that of CK after 16 days treatment time. The results indicated that YE can induce more synthesis of tropane alkaloids by increasing the activity of key enzymes in nitrogen metabolism to provide more synthetic materials for secondary metabolism, meanwhile it regulated the expression level of some genes of key metabolic enzyme to accelerate secondary metabolism.

The positive function of selenium supplementation on reducing nitrate accumulation in hydroponic lettuce (Lactuca sativa L.)

High nitrate (NO3−) in vegetables, especially in leaf vegetables poses threaten to human health. Selenium (Se) is an important element for maintaining human health, and exogenous Se application during vegetable and crop production is an effective way to prevent Se deficiency in human bodies. Exogenous Se shows positive function on plant growth and nutrition uptake under abiotic and/or biotic stresses. However, the influence of exogenous Se on NO3− accumulation in hydroponic vegetables is still not clear. In the present study, hydroponic lettuce plants were subjected to six different concentrations (0, 0.1, 0.5, 5, 10 and 50 µmol L−1) of Se as Na2SeO3. The effects of Se on NO3− content, plant growth, and photosynthetic capacity of lettuce (Lactuca sativa L.) were investigated. The results showed that exogenous Se positively decreased NO3− content and this effect was concentration-dependent. The lowest NO3− content was obtained under 0.5 µmol L−1 Se treatment. The application of Se enhanced photosynthetic capacity by increasing the photosynthesis rate (Pn), stomatal conductance (Cs) and the transpiration efficiency (Tr) of lettuce. The transportation and assimilation of NO3− and activities of nitrogen metabolism enzymes in lettuce were also analysed. The NO3− efflux in the lettuce roots was markedly increased, but the efflux of NO3− from the root to the shoot was decreased after treated with exogenous Se. Moreover, Se application stimulated NO3− assimilation by enhancing nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase enzyme (GOGAT) activities. These results provide direct evidence that exogenous Se shows positive function on decreasing NO3− accumulation via regulating the transport and enhancing activities of nitrogen metabolism enzyme in lettuce. We suggested that 0.5 µmol L−1 Se can be used to reduce NO3− content and increase hydroponic lettuce yield.

Effects of spraying paclobutrazol at different stages on physiological characteristics, yield and quality of peanut

To explore the optimum stage of spraying with paclobutrazol (PBZ) for different peanut cultivars under high yield condition, we investigated the effects of spraying PBZ at different stages on chlorophyll content, root activity, protective enzymes, nitrogen and carbon metabolism enzymes of leaves, pod yield and kernel quality of peanut, with Huayu 20 and Huayu 25 as materials. The results showed that spraying PBZ at different stages increased root activity, chlorophyll content, SOD, POD, CAT, SS, SPS, PEPC activities and decreased the MDA content, NR, GS, GDH and GOGAT activities for pod setting stage of two cultivars. These results suggested that the effects would be more obvious at earlier spray time. For HY25, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 25 cm. For HY20, spraying PBZ when the main stem height was 25 cm decreased the activities of protective enzymes. Earlier spraying time to HY20 would lead to early senescence, lower chlorophyll content, root activity and carbon metabolism enzyme activity. For HY20, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 30 cm. Our results indicated that PBZ treatments at the optimum stage could improve pod yield and economic coefficient of both cultivars and enhance the fat content and the relative content of oleic acid and the O/L. Under high yield condition, the optimum stage of spraying PBZ was 25 cm height of the main stem for HY25 and 30 cm for HY20.

Impact of treated wastewater and salicylic acid on physiological performance, malformation and yield of two mango cultivars

Abstract Limitation of fresh water for agriculture irrigation is a worldwide problem, especially in countries located in the arid region like Egypt. This work demonstrates the impact of treated wastewater on two mango cultivars, cv. “Keitt” and cv. “Ewais”. Treated wastewater contains comparatively more contaminant than fresh water, therefore salicylic acid (SA) was added to the treated wastewater to study their combined impact on mango cultivars. Observation indicated that both cultivars positively responded to treated wastewater and/or SA in a similar manner regarding growth, yield and fruit quality parameters. Obtained data revealed that treated wastewater and/or SA promoted vegetative growth and exhibited inhibitory role on the occurrence of malformation and fruitlet abscission. Studied biochemical features related to lipid peroxidation and oxidative system were differently affected. Cultivar “Keitt” had higher activity of catalase, peroxidase, and superoxide dismutase. as compared to cv. “Ewais”. In the resistant cv. “Keitt” the constitutive level of lipid peroxidation was lower, but the activity of enzymatic antioxidants and non-enzymatic antioxidants was higher than the susceptible cultivar “Ewais”. Similarly, Nitrogen metabolism enzymes and photosynthetic performance were inherently higher in cv. “Keitt”. The comparative analysis between the two mango cultivars, based on malformation percentage analysis, indicated that cv. “Keitt” can be categorized into the tolerant group (1–10%), whereas cv. “Ewais” into susceptible ones (20–40%). Our results suggested that cv. “Keitt” possess better protection mechanisms against oxidative damage as compared to the relatively susceptible cultivar “Ewais”. It is based on maintaining higher inherited and increased activity of the antioxidant system. Our work underlines the relation between malformation tolerance and antioxidant defence system. In this work, we suggest the performance of antioxidant defence system as a potential biochemical indicator for screening mango genotypes for malformation behaviour.

Structural and functional indices of isolated hepatocytes of rats in the presence of nanoparticles based on europium and gadolinium

The effect of nanoparticles based on europium and gadolinium GdVO4:Eu3+(-) on the pro-antioxidant balance and the activity of a number of enzymes of isolated rat hepatocytes was studied. The relevance of the work is connected with research aimed at studying the mechanisms of interaction of nanoparticles with components of cells of biological objects. To correct some metabolic disturbances, redox-active nanoparticles based on rare-earth metals are promising. Some of them are nanoparticles based on europium and gadolinium GdVO4:Eu3+(-). These nanoparticles have a spherical shape, a charge, can penetrate into cells, are redoxactive. However, it is not known with which molecules and supramolecular complexes they can interact and through this affect metabolism. The purpose of this study was to study the pro-antioxidant balance, the activity of glutathione metabolism enzymes, as well as the activity of some enzymes of rat hepatocyte nitrogen exchange in the presence of europium-based gadolinium and gadolinium GdVO4:Eu3+(-). Hepatocytes were incubated with nanoparticles for 2 and 14 hours, then lysed, and in lysates, LPO parameters, catalase and enzyme metabolism of glutathione, SH group content, activity of nitrogen exchange enzymes – alanine-, aspartate-, tyrosine aminotransferases and arginase were determined. In the incubation medium, the activity of LDH and aminotransferases as markers of membrane damage was determined. It was established that incubation with nanoparticles did not cause LPO enhancement and damage of plasma membranes of hepatocytes. The effect of these nanoparticles on the content of thiol groups and the activity of glutathione metabolism enzymes has been revealed, which may indicate their ability to influence the state of the glutathione unit of the antioxidant defense system. The incubation of hepatocytes with nanoparticles had practically no effect on the activity of the enzymes of nitrogen metabolism, which is evidence of the local action of nanoparticles based on europium and gadolinium GdVO4:Eu3+(-) in cells.

Effects of Soil Water Deficit on Insecticidal Protein Expression in Boll Shells of Transgenic Bt Cotton and the Mechanism.

This study was conducted to investigate the effects of soil water deficit on insecticidal protein expression in boll shells of cotton transgenic for a Bt gene. In 2014, Bt cotton cultivars Sikang 1 (a conventional cultivar) and Sikang 3 (a hybrid cultivar) were planted in pots and five soil water content treatments were imposed at peak boll stage: 15% (G1), 35% (G2), 40% (G3), 60% (G4), and 75% field capacity (CK), respectively. Four treatments (G2, G3, G4, and CK) were repeated in 2015 in the field. Results showed that the insecticidal protein content of boll shells decreased with increasing water deficit. Compared with CK, boll shell insecticidal protein content decreased significantly when soil water content was below 60% of maximum water holding capacity for Sikang 1 and Sikang 3. However, increased Bt gene expression was observed when boll shell insecticidal protein content was significantly reduced. Activity assays of key enzymes in nitrogen metabolism showed that boll shell protease and peptidase increased but nitrogen reductase and glutamic-pyruvic transaminase (GPT) decreased. Insecticidal protein content exhibited significant positive correlation with nitrogen reductase and GPT activities; and significant negative correlation with protease and peptidase activities. These findings suggest that the decrease of insecticidal protein content associated with increasing water deficit was a net result of decreased synthesis and increased decomposition.

Differential inhibition of adenylylated and deadenylylated forms of M. tuberculosis glutamine synthetase as a drug discovery platform

Glutamine synthetase is a ubiquitous central enzyme in nitrogen metabolism that is controlled by up to four regulatory mechanisms, including adenylylation of some or all of the twelve subunits by adenylyl transferase. It is considered a potential therapeutic target for the treatment of tuberculosis, being essential for the growth of Mycobacterium tuberculosis, and is found extracellularly only in the pathogenic Mycobacterium strains. Human glutamine synthetase is not regulated by the adenylylation mechanism, so the adenylylated form of bacterial glutamine synthetase is of particular interest. Previously published reports show that, when M. tuberculosis glutamine synthetase is expressed in Escherichia coli, the E. coli adenylyl transferase does not optimally adenylylate the M. tuberculosis glutamine synthetase. Here, we demonstrate the production of soluble adenylylated M. tuberulosis glutamine synthetase in E. coli by the co-expression of M. tuberculosis glutamine synthetase and M. tuberculosis adenylyl transferase. The differential inhibition of adenylylated M. tuberulosis glutamine synthetase and deadenylylated M. tuberulosis glutamine synthetase by ATP based scaffold inhibitors are reported. Compounds selected on the basis of their enzyme inhibition were also shown to inhibit M. tuberculosis in the BACTEC 460TB™ assay as well as the intracellular inhibition of M. tuberculosis in a mouse bone-marrow derived macrophage assay.

Activities of Carbon and Nitrogen Metabolism Enzymes during Germinating Sorghum Seeds and Early Seedlings Growth

Carbon and nitrogen metabolism are regulated by complex mechanisms in order to optimize growth and development of plants and play a major role during germination and post-germinative growth. The objective of the current work was to establish the degree of changes in activities of key enzymes implicated in these two metabolism pathways during germination and post-germinative growth such as; glutamine synthetase, glutamate dehydrogenase, phosphoenolpyruvate carboxylase, malate dehydrogenase, isocitrate dehydrogenase and aspartate aminotransferase. We have observed that during germination and seedlings development the most activities of nitrogen and carbon metabolism enzymes were correlated (nearly show similar kinetic changes) and influenced by their cellular environment and developmental stage. Therefore, higher activities of these enzymes were observed in the seed, root and shoot at early stages of the post-germinative phase could be effectively linked to the demand of de novo proteins to ensure a good development of seedlings.

Photosynthesis, Metabolite Composition and Anatomical Structure of Oryza sativa and Two Wild Relatives, O. grandiglumis and O. alta

Photosynthesis, enzyme activities and metabolite pools associated with primary carbon metabolism in leaves were studied in O. grandiglumis and O. alta (wild relatives of rice which produce high biomass) versus O. sativa (a japonica cultivar and a indica-japonica hybrid) to assess their potential for identifying traits which might be utilized to enhance rice productivity. The wild relatives had higher rates of photosynthesis on a fresh weight basis, and higher water use efficiency than the O. sativa lines. There were no striking differences in activities of a number of key enzymes in carbon and nitrogen metabolism between the wild relatives and cultivated rice lines. Along with higher rates of photosynthesis on a fresh weight basis, the leaves of the two wild species had higher nitrate content, higher levels of starch, glucose and fructose, and higher levels of organic acids (malate, succinate and acetate), compared to the O. sativa lines. The results suggested that O. grandiglumis and O. alta have differences in physiology and primary metabolism which might be exploited to improve growth and productivity of cultivated rice.

Cytomorphological and nitrogen metabolic enzyme analysis of psychrophilic and mesophilic Nostoc sp.: a comparative outlook

Cyanobacterial diazotrophs play a significant role in environmental nitrogen economy despite their habitat either tropical or polar. However, the phenomenon by which it copes with temperature induced stress is poorly understood. Temperature response study of psychrophilic and mesophilic Nostoc strains explores their adaptive mechanisms. The selected psychrophilic and mesophilic strains were confirmed as Nostoc punctiforme and Nostoc calcicola respectively, by ultrastructure and 16S rDNA phylogeny. The psychrophilic strain has extensive glycolipid and polysaccharide sheath along with characteristic deposition of cyanophycin, polyhydroxybutyrate granules, and carboxysomes. This is possibly an adaptive strategy exhibited to withstand the freezing temperature and high intense of ultraviolet rays. The biomass measured in terms of dry weight, protein, and chlorophyll indicated a temperature dependant shift in both the psychrophilic and mesophilic strains and attained maximum growth in their respective temperature niches. At low temperature, psychrophilic organism exhibited nitrogenase activity, while mesophilic strains did not. The maximum glutamine synthetase activity was observed at 4 °C for psychrophilic and 37 °C for mesophilic strains. Activity at 4 °C in psychrophilic strains revealed their energetic mechanism even at low temperature. The nitrate and nitrite reductase of both psychrophilic and mesophilic strains showed maximum activity at 37 °C denoting their similar nitrogen assimilating mechanisms for combined nitrogen utilization. The activity studies of nitrogen fixation/assimilation enzymes have differential effects at varying temperatures, which provide valuable insights of physiological contribution and role of Nostoc strains in the biological nitrogen cycle.

Effect of exogenously applied molybdenum on its absorption and nitrate metabolism in strawberry seedlings

Molybdenum (Mo)—an essential element of plants—is involved in nitrogen (N) metabolism. Plants tend to accumulate more nitrate and show lower nitrogen use efficiency (NUE) under Mo-deficient conditions. Improving NUE in fruits reduces the negative effect of large applications of chemical fertilizer, but the mechanisms underlying how Mo enhances NUE remain unclear. We cultivated strawberry seedlings sprayed with 0, 67.5, 135, 168.75, or 202.5 g Mo·ha−1 in a non-soil culture system. The Mo concentration in every plant tissue analyzed increased gradually as Mo application level rose. Mo application affected iron, copper, and selenium adsorption in roots. Seedlings sprayed with 135 g Mo·ha−1 had a higher [15N] shoot:root (S:R) ratio, and 15NUE, and produced higher molybdate transporter type 1 (MOT1) expression levels in the roots and leaves. Seedlings sprayed with 135 g Mo·ha−1 also had relatively high nitrogen metabolic enzyme activities and up-regulated transcript levels of nitrate uptake genes (NRT1.1; NRT2.1) and nitrate-responsive genes. Furthermore, there was a significantly lower NO3− concentration in the leaves and roots, a higher NH4+ concentration in leaves, and a higher glutamine/glutamate (Gln/Glu) concentration at 135 g Mo·ha−1. Seedlings sprayed with 202.5 g Mo·ha−1 showed the opposite trend. Taken together, these results suggest that a 135 g Mo·ha−1 application was optimal because it enhanced NO3− transport from the roots to the shoots and increased NUE by mediating nitrogen metabolic enzyme activities, nitrate transport, and nitrate assimilation gene activities.