scholarly journals Excessive assimilation of ammonium by plastidic glutamine synthetase is a major cause of ammonium toxicity in Arabidopsis thaliana

2019 ◽  
Author(s):  
Takushi Hachiya ◽  
Jun Inaba ◽  
Mayumi Wakazaki ◽  
Mayuko Sato ◽  
Kiminori Toyooka ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrate Assimilation ◽  
Nitrogen Sources ◽  
Ammonium Assimilation ◽  
Ammonia Solution ◽  
Acidic Stress ◽  
Ammonium Toxicity ◽  
Ammonium Accumulation ◽  
Concomitant Reduction ◽  
High Concentrations

AbstractPlants use nitrate and ammonium in the soil as their main nitrogen sources. Recently, ammonium has attracted attention due to evidence suggesting that, in C3 species, an elevated CO2 environment inhibits nitrate assimilation. However, high concentrations of ammonium as the sole nitrogen source for plants causes impaired growth, i.e. ammonium toxicity. Although ammonium toxicity has been studied for a long time, the primary cause remains to be elucidated. Here, we show that ammonium assimilation in plastids rather than ammonium accumulation is a primary cause for toxicity. Our genetic screen of ammonium-tolerant Arabidopsis lines with enhanced shoot growth identified plastidic GLUTAMINE SYNTHETASE 2 (GLN2) as the causal gene. Our reciprocal grafting of wild-type and GLN2 or GLN1;2-deficient lines suggested that shoot GLN2 activity results in ammonium toxicity, whilst root GLN1;2 activity prevents it. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the toxic ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress in the shoot. This fundamental insight provides a framework for enhanced understanding of ammonium toxicity in plants.

scholarly journals Excessive ammonium assimilation by plastidic glutamine synthetase causes ammonium toxicity in Arabidopsis thaliana

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Takushi Hachiya ◽  
Jun Inaba ◽  
Mayumi Wakazaki ◽  
Mayuko Sato ◽  
Kiminori Toyooka ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Sources ◽  
Ammonium Assimilation ◽  
Ammonia Solution ◽  
Acidic Stress ◽  
Ammonium Toxicity ◽  
Ammonium Accumulation ◽  
Concomitant Reduction ◽  
Ammonium Nutrition ◽  
Near Future

AbstractPlants use nitrate, ammonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest. However, abundant ammonium nutrition impairs growth, i.e., ammonium toxicity, the primary cause of which remains to be determined. Here, we show that ammonium assimilation by GLUTAMINE SYNTHETASE 2 (GLN2) localized in the plastid rather than ammonium accumulation is a primary cause for toxicity, which challenges the textbook knowledge. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress.

scholarly journals Regulation of synthesis of glutamate dehydrogenase and glutamine synthetase in micro-organisms

1969 ◽  
Vol 115 (4) ◽  
pp. 769-775 ◽  
Author(s):  
J. A. Pateman
Keyword(s):  
Escherichia Coli ◽  
Glutamine Synthetase ◽  
Glutamate Dehydrogenase ◽  
Nitrogen Sources ◽  
Sole Source ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Escherichia Coli Cells ◽  
High Concentrations ◽  
Micro Organisms

1. Aspergillus nidulans, Neurospora crassa and Escherichia coli were grown on media containing a range of concentrations of nitrate, or ammonia, or urea, or l-glutamate, or l-glutamine as the sole source of nitrogen and the glutamate dehydrogenate and glutamine synthetase of the cells measured. 2. Aspergillus, Neurospora and Escherichia coli cells, grown on l-glutamate or on high concentrations of ammonia or on high concentrations of urea, possessed low glutamate dehydrogenase activity compared with cells grown on other nitrogen sources. 3. Aspergillus, Neurospora and Escherichia coli cells grown on l-glutamate possessed high glutamine synthetase activity compared with cells grown on other nitrogen sources. 4. The hypothesis is proposed that in Aspergillus, Neurospora and Escherichia colil-glutamate represses the synthesis of glutamate dehydrogenase and l-glutamine represses the synthesis of glutamine synthetase. 5. A comparison of the glutamine-synthesizing activity and the γ-glutamyltransferase activity of glutamine synthetase in Aspergillus and Neurospora gave no indication that these fungi produce different forms of glutamine synthetase when grown on ammonia or l-glutamate as nitrogen sources.

scholarly journals Lack of Correlation between Ammonium Accumulation and Survival of Transgenic Birch Plants with Pine Cytosolic Glutamine Synthetase Gene after “Basta” Herbicide Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Vadim Lebedev ◽  
Vyacheslav Faskhiev ◽  
Konstantin Shestibratov
Keyword(s):  
Transgenic Plants ◽  
Glutamine Synthetase ◽  
Leaf Tissue ◽  
Ammonium Toxicity ◽  
Ammonium Accumulation ◽  
Herbicide Treatment ◽  
Genes Encoding ◽  
Transgenic Lines ◽  
On Line ◽  
Increase Productivity

Transformation of plants with genes encoding a glutamine synthetase (GS), a key nitrogen metabolism enzyme, is usually used to increase productivity. However, overexpression of these genes may increase resistance to phosphinothricin (PPT) that irreversibly inhibits GS causing ammonium accumulation in plant tissues. Transgenic plants of two birch (Betula pubescens) genotypes expressing a pine cytosolic GS gene were used for studying the PPT effect on trees. Two control and 8 transgenic lines were treated with herbicide “Basta” at dose equivalent to 2.5 and 5 Lha−1. Necrosis and abscission of leaves occurred irrespective of a transgenic status or the treatment dose. Ammonium content in leaf tissue in 3 days after the 5 Lha−1 treatment was substantially increased in all plants, 3.2–16.0 times depending on line. After the 2.5 Lha−1 treatment, ammonium content in three transgenic lines was not different from that in control variant sprayed with water. The herbicide treatment caused more prominent desiccation in the bp3f1 genotype nontransgenic plants as compared to transgenic plants, but not in the bp4a genotype. Lack of correlation between ammonium levels and survival of transgenic plants suggests that ammonium toxicity is not a main reason for the birch plant death after the PPT treatment.

Preferential nitrate immobilization in alkaline soils

Soil Research ◽  
1992 ◽  
Vol 30 (5) ◽  
pp. 737 ◽  
Author(s):  
IJ Rochester ◽  
GA Constable ◽  
DA Macleod
Keyword(s):  
Acid Soil ◽  
Nitrification Inhibitor ◽  
Biological Significance ◽  
Nitrate Assimilation ◽  
Acid Soils ◽  
Ammonium Assimilation ◽  
Potassium Nitrate ◽  
Alkaline Soil ◽  
Alkaline Soils ◽  
Nitrate Immobilization

The literature pertaining to N immobilization indicates that ammonium is immobilized in preference to nitrate. Our previous research in an alkaline clay soil has indicated substantial immobilization of nitrate. To verify the preference for immobilization of nitrate or ammonium by the microbial biomass in this and other soil types, the immobilization of ammonium and nitrate from applications of ammonium sulfate and potassium nitrate following the addition of cotton crop stubble was monitored in six soils. The preference for ammonium or nitrate immobilization was highly correlated with each soil's pH, C/N ratio and its nitrification capacity. Nitrate was immobilized in preference to ammonium in neutral and alkaline soils; ammonium was preferentially immobilized in acid soils. No assimilation of nitrate (or nitrification) occurred in the most acid soil. Similarly, little assimilation of ammonium occurred in the most alkaline soil. Two physiological pathways, the nitrate assimilation pathway and the ammonium assimilation pathway, appear to operate concurrently; the dominance of one pathway over the other is indicated by soil pH. The addition of a nitrification inhibitor to an alkaline soil enhanced the immobilization of ammonium. Recovery of 15N confirmed that N was not denitrified, but was biologically immobilized. The immobilization of 1 5 ~ and the apparent immobilization of N were similar in magnitude. The identification of preferential nitrate immobilization has profound biological significance for the cycling of N in alkaline soils.

scholarly journals Reticulate evolution in eukaryotes: origin and evolution of the nitrate assimilation pathway

2018 ◽  
Author(s):  
Eduard Ocaña-Pallarès ◽  
Sebastián R. Najle ◽  
Claudio Scazzocchio ◽  
Iñaki Ruiz-Trillo
Keyword(s):  
Nitrate Reductase ◽  
Gene Fusion ◽  
Evolutionary History ◽  
Transcriptional Control ◽  
Genetic Material ◽  
Nitrate Assimilation ◽  
Nitrogen Sources ◽  
Reticulate Evolution ◽  
Origin And Evolution ◽  
Ideal Object

AbstractGenes and genomes can evolve through interchanging genetic material, this leading to reticular evolutionary patterns. However, the importance of reticulate evolution in eukaryotes, and in particular of horizontal gene transfer (HGT), remains controversial. Given that metabolic pathways with taxonomically-patchy distributions can be indicative of HGT events, the eukaryotic nitrate assimilation pathway is an ideal object of investigation, as previous results revealed a patchy distribution and suggested one crucial HGT event. We studied the evolution of this pathway through both multi-scale bioinformatic and experimental approaches. Our taxon-rich genomic screening shows this pathway to be present in more lineages than previously proposed and that nitrate assimilation is restricted to autotrophs and to distinct osmotrophic groups. Our phylogenies show a pervasive role of HGT, with three bacterial transfers contributing to the pathway origin, and at least seven well-supported transfers between eukaryotes. Our results, based on a larger dataset, differ from the previously proposed transfer of a nitrate assimilation cluster from Oomycota (Stramenopiles) to Dikarya (Fungi, Opisthokonta). We propose a complex HGT path involving at least two cluster transfers between Stramenopiles and Opisthokonta. We also found that gene fusion played an essential role in this evolutionary history, underlying the origin of the canonical eukaryotic nitrate reductase, and of a novel nitrate reductase in Ichthyosporea (Opisthokonta). We show that the ichthyosporean pathway, including this novel nitrate reductase, is physiologically active and transcriptionally co-regulated, responding to different nitrogen sources; similarly to distant eukaryotes with independent HGT-acquisitions of the pathway. This indicates that this pattern of transcriptional control evolved convergently in eukaryotes, favoring the proper integration of the pathway in the metabolic landscape. Our results highlight the importance of reticulate evolution in eukaryotes, by showing the crucial contribution of HGT and gene fusion in the evolutionary history of the nitrate assimilation pathway.

scholarly journals Recycling and Conversion of Yeasts into Organic Nitrogen Sources for Wine Fermentation: Effects on Molecular and Sensory Attributes

Fermentation ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 313
Author(s):  
Paula Rojas ◽  
Daniel Lopez ◽  
Francisco Ibañez ◽  
Camila Urbina ◽  
Wendy Franco ◽  
...  
Keyword(s):  
Organic Nitrogen ◽  
Protein Hydrolysate ◽  
Principal Component ◽  
Nitrogen Sources ◽  
Isoamyl Alcohol ◽  
Positive Influence ◽  
Higher Alcohols ◽  
Fermentation Performance ◽  
High Concentrations ◽  
Significant Positive Influence

Organic nitrogen plays a significant role in the fermentation performance and production of esters and higher alcohols. This study assessed the use of yeast protein hydrolysate (YPH) as a nitrogen source for grape must fermentation. In this study, we prepared an enzymatic protein hydrolysate using yeasts recovered from a previous fermentation of wine. Three treatments were performed. DAP supplementation was used as a control, while two YPH treatments were used. Low (LDH) and high degrees of hydrolysis (HDH), 3.5% and 10%, respectively, were chosen. Gas chromatography and principal component analysis indicated a significant positive influence of YPH-supplementations on the production of esters and higher alcohols. Significantly high concentrations of 3-methyl-1-penthanol, isoamyl alcohol, isobutanol, and 2-phenylethanol were observed. Significant odorant activity was obtained for 3-methyl-1-pentanol and ethyl-2-hexenoate. The use of YPH as nitrogen supplementation is justified as a recycling yeasts technique by the increase in volatile compounds.

The Effect of Bialaphos on Ammonium-Assimilation and Photosynthesis II. Effect on Photosynthesis and Photorespiration

1989 ◽  
Vol 44 (1-2) ◽  
pp. 103-108 ◽  
Author(s):  
Christine Ziegler ◽  
Aloysius Wild
Keyword(s):  
Amino Acids ◽  
Glutamine Synthetase ◽  
Previous Investigation ◽  
Ammonium Assimilation ◽  
Atmospheric Conditions ◽  
Direct Inhibition ◽  
Rubp Carboxylase ◽  
Photosynthesis Inhibition

Abstract The application of bialaphos (phosphinothricyl-alanyl-alanine) effects a quick photosynthesis inhibition under atmospheric conditions (400 ppm CO2, 21% O2). However, under conditions (1000 ppm CO2, 2% O2) under which photorespiration cannot occur there is no photosynthesis inhibition. In the previous investigation it could be shown that bialaphos splits in plants into phosphinothricin and alanine. The inhibition of glutamine synthetase through freed phosphinothricin results in an NH4+-accumulation and a decrease in glutamine. With the addition of glutamine, photosynthesis inhibition by bialaphos can be reduced. An NH4+-accumulation takes place under atmospheric conditions as well as under non-photorespiratory conditions; though in the latter case, in less amounts. After adding glutamine and other amino acids the NH4+-accumulation increases especially. This indicates that NH4+-accumulation cannot be the primary cause for photosynthesis inhibition by bialaphos. The investigations indicate that for the effectiveness of either bialaphos or phosphinothricin, a process in connexion with photorespiration plays a considerable role. The glyoxylate transamination in photorespiration could be inhibited, which results probably on a glyoxylate accumulation. Corresponding investigations showed inhibition of photosynthesis as well as a direct inhibition of RubP-carboxylase with glyoxylate.

scholarly journals Inactivation of gltB Abolishes Expression of the Assimilatory Nitrate Reductase Gene (nasB) in Pseudomonas putida KT2442

2000 ◽  
Vol 182 (12) ◽  
pp. 3368-3376 ◽  
Author(s):  
Leo Eberl ◽  
Aldo Ammendola ◽  
Michael H. Rothballer ◽  
Michael Givskov ◽  
Claus Sternberg ◽  
...  
Keyword(s):  
Nitrate Reductase ◽  
Pseudomonas Putida ◽  
Nitrogen Starvation ◽  
Nitrate Assimilation ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Nucleotide Sequence Analysis ◽  
Nitrate Reductase Gene ◽  
Physiological Characterization ◽  
Reductase Gene

ABSTRACT By using mini-Tn5 transposon mutagenesis, random transcriptional fusions of promoterless bacterial luciferase,luxAB, to genes of Pseudomonas putida KT2442 were generated. Insertion mutants that responded to ammonium deficiency by induction of bioluminescence were selected. The mutant that responded most strongly was genetically analyzed and is demonstrated to bear the transposon within the assimilatory nitrate reductase gene (nasB) of P. putida KT2442. Genetic evidence as well as sequence analyses of the DNA regions flanking nasBsuggest that the genes required for nitrate assimilation are not clustered. We isolated three second-site mutants in which induction ofnasB expression was completely abolished under nitrogen-limiting conditions. Nucleotide sequence analysis of the chromosomal junctions revealed that in all three mutants the secondary transposon had inserted at different sites in the gltB gene of P. putida KT2442 encoding the major subunit of the glutamate synthase. A detailed physiological characterization of thegltB mutants revealed that they are unable to utilize a number of potential nitrogen sources, are defective in the ability to express nitrogen starvation proteins, display an aberrant cell morphology under nitrogen-limiting conditions, and are impaired in the capacity to survive prolonged nitrogen starvation periods.

scholarly journals Biochemical Background and Compartmentalized Functions of Cytosolic Glutamine Synthetase for Active Ammonium Assimilation in Rice Roots

2004 ◽  
Vol 45 (11) ◽  
pp. 1640-1647 ◽  
Author(s):  
Keiki Ishiyama ◽  
Eri Inoue ◽  
Mayumi Tabuchi ◽  
Tomoyuki Yamaya ◽  
Hideki Takahashi
Keyword(s):  
Glutamine Synthetase ◽  
Ammonium Assimilation ◽  
Rice Roots ◽  
Cytosolic Glutamine Synthetase

scholarly journals In Vivo Regulation of Glutamine Synthetase Activity in the Marine Chlorophyll b-Containing CyanobacteriumProchlorococcus sp. Strain PCC 9511 (Oxyphotobacteria)

2001 ◽  
Vol 67 (5) ◽  
pp. 2202-2207 ◽  
Author(s):  
Sabah El Alaoui ◽  
Jesús Diez ◽  
Lourdes Humanes ◽  
Fermı́n Toribio ◽  
Frédéric Partensky ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Starvation ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Determination ◽  
Physiological Regulation ◽  
Gs Protein

ABSTRACT The physiological regulation of glutamine synthetase (GS; EC6.3.1.2 ) in the axenic Prochlorococcus sp. strain PCC 9511 was studied. GS activity and antigen concentration were measured using the transferase and biosynthetic assays and the electroimmunoassay, respectively. GS activity decreased when cells were subjected to nitrogen starvation or cultured with oxidized nitrogen sources, which proved to be nonusable forProchlorococcus growth. The GS activity in cultures subjected to long-term phosphorus starvation was lower than that in equivalent nitrogen-starved cultures. Azaserine, an inhibitor of glutamate synthase, provoked an increase in enzymatic activity, suggesting that glutamine is not involved in GS regulation. Darkness did not affect GS activity significantly, while the addition of diuron provoked GS inactivation. GS protein determination showed that azaserine induces an increase in the concentration of the enzyme. The unusual responses to darkness and nitrogen starvation could reflect adaptation mechanisms of Prochlorococcus for coping with a light- and nutrient-limited environment.

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