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 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 RELATION OF AMMONIUM ACCUMULATION AND ETHYLENE BIOSYNTHESIS IN EXPRESSION OF PHYSIOLOGICAL STRESS IN PLANTS

HortScience ◽  
1991 ◽  
Vol 26 (5) ◽  
pp. 482e-482
Author(s):  
Allen V. Barker ◽  
Kathleen M. Ready ◽  
Jinan Feng
Keyword(s):  
Physiological Stress ◽  
Ethylene Biosynthesis ◽  
Solution Culture ◽  
Root Knot Nematode ◽  
Ethylene Evolution ◽  
Ammonium Toxicity ◽  
Ammonium Accumulation ◽  
Ethylene Action ◽  
Ammonium Nutrition ◽  
Oxyacetic Acid

Several factors inducing physiological stress in plants were investigated for their effects on foliar ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.). Plants grown on ammonium nutrition (0.015M NH4+) in solution culture had elevated rates of ammonium accumulation and ethylene evolution relative to plants grown on nitrate nutrition at the same molar concentration. Inhibitors of ethylene action (0.001 mM Ag+) or synthesis (0.01 mM amino-oxyacetic acid) restricted ammonium accumulation and ethylene evolution relative to rates by untreated controls receiving ammonium nutrition. The inhibitors lessened the expression of ammonium toxicity. Stress from salinity, drought, or flooding in soil increased ammonium accumulation and ethylene evolution. Plants infected with root-knot nematode had variable rates of ethylene evolution in response to variations in ammonium accumulation. Ammonium accumulation and ethylene evolution appear to be factors in the expression of physiological stress.

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.

Over-expression of the rice OsAMT1-1 gene increases ammonium uptake and content, but impairs growth and development of plants under high ammonium nutrition

2006 ◽  
Vol 33 (2) ◽  
pp. 153 ◽  
Author(s):  
Mohammad S. Hoque ◽  
Josette Masle ◽  
Michael K. Udvardi ◽  
Peter R. Ryan ◽  
Narayana M. Upadhyaya
Keyword(s):  
Transgenic Plants ◽  
Ammonium Assimilation ◽  
Ammonium Transporter ◽  
Ammonium Uptake ◽  
Vegetative Stage ◽  
Over Expression ◽  
Transgenic Lines ◽  
Ammonium Nutrition ◽  
Maize Ubiquitin Promoter

A transgenic approach was undertaken to investigate the role of a rice ammonium transporter (OsAMT1-1) in ammonium uptake and consequent ammonium assimilation under different nitrogen regimes. Transgenic lines overexpressing OsAMT1-1 were produced by Agrobacterium-mediated transformation of two rice cultivars, Taipei 309 and Jarrah, with an OsAMT1-1 cDNA gene construct driven by the maize ubiquitin promoter. Transcript levels of OsAMT1-1 in both Taipei 309 and Jarrah transgenic lines correlated positively with transgene copy number. Shoot and root biomass of some transgenic lines decreased during seedling and early vegetative stage compared to the wild type, especially when grown under high (2 mm) ammonium nutrition. Transgenic plants, particularly those of cv. Jarrah recovered in the mid-vegetative stage under high ammonium nutrition. Roots of the transgenic plants showed increased ammonium uptake and ammonium content. We conclude that the decreased biomass of the transgenic lines at early stages of growth might be caused by the accumulation of ammonium in the roots owing to the inability of ammonium assimilation to match the greater ammonium uptake.

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 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.

scholarly journals The sRNA NsiR4 is involved in nitrogen assimilation control in cyanobacteria by targeting glutamine synthetase inactivating factor IF7

2015 ◽  
Vol 112 (45) ◽  
pp. E6243-E6252 ◽  
Author(s):  
Stephan Klähn ◽  
Christoph Schaal ◽  
Jens Georg ◽  
Desirée Baumgartner ◽  
Gernot Knippen ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Metabolism ◽  
Nitrogen Assimilation ◽  
Nitrogen Sources ◽  
Transcriptome Profiling ◽  
Site Directed Mutagenesis ◽  
Reporter System ◽  
Available Nitrogen ◽  
Mrna Accumulation

Glutamine synthetase (GS), a key enzyme in biological nitrogen assimilation, is regulated in multiple ways in response to varying nitrogen sources and levels. Here we show a small regulatory RNA, NsiR4 (nitrogen stress-induced RNA 4), which plays an important role in the regulation of GS in cyanobacteria. NsiR4 expression in the unicellularSynechocystissp. PCC 6803 and in the filamentous, nitrogen-fixingAnabaenasp. PCC 7120 is stimulated through nitrogen limitation via NtcA, the global transcriptional regulator of genes involved in nitrogen metabolism. NsiR4 is widely conserved throughout the cyanobacterial phylum, suggesting a conserved function. In silico target prediction, transcriptome profiling on pulse overexpression, and site-directed mutagenesis experiments using a heterologous reporter system showed that NsiR4 interacts with the 5′UTR ofgifAmRNA, which encodes glutamine synthetase inactivating factor (IF)7. InSynechocystis, we observed an inverse relationship between the levels of NsiR4 and the accumulation of IF7 in vivo. This NsiR4-dependent modulation ofgifA(IF7) mRNA accumulation influenced the glutamine pool and thusNH4+assimilation via GS. As a second target, we identifiedssr1528, a hitherto uncharacterized nitrogen-regulated gene. Competition experiments between WT and an ΔnsiR4KO mutant showed that the lack of NsiR4 led to decreased acclimation capabilities ofSynechocystistoward oscillating nitrogen levels. These results suggest a role for NsiR4 in the regulation of nitrogen metabolism in cyanobacteria, especially for the adaptation to rapid changes in available nitrogen sources and concentrations. NsiR4 is, to our knowledge, the first identified bacterial sRNA regulating the primary assimilation of a macronutrient.

Sign in / Sign up

Export Citation Format

Share Document