Ammonium stress in Arabidopsis: signaling, genetic loci, and physiological targets

Li, Baohai; Li, Guangjie; Kronzucker, Herbert J.; Baluška, Frantǐsek; Shi, Weiming

doi:10.1016/j.tplants.2013.09.004

Cited by 220 publications

(185 citation statements)

References 79 publications

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“…However, ammonium translocation to the shoot will inevitably increase (Finnemann and Schjoerring, 1999;Schjoerring et al, 2002). Arabidopsis shoots are believed to be significantly more sensitive to ammonium stress than roots (Li et al, 2014). In this work, Arabidopsis plants exposed to the high ammonium treatment developed clear ammonium toxicity symptoms in the form of leaf chlorosis, reduced plant growth, increased tissue ammonium content, and changed amino acid composition (Figs.…”

Section: Discussionmentioning

confidence: 70%

Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity

et al. 2016

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Cytosolic GS1 (Gln synthetase) is central for ammonium assimilation in plants. High ammonium treatment enhanced the expression of the GS1 isogene Gln-1;2 encoding a low-affinity high-capacity GS1 protein in Arabidopsis (Arabidopsis thaliana) shoots. Under the same conditions, the expression of the high-affinity low-capacity isoform Gln-1;1 was reduced. The expression of Gln-1;3 did not respond to ammonium treatment while Gln-1;4 and Gln-1;5 isogenes in all cases were expressed at a very low level. Gln-2 was highly expressed in shoots but only at a very low level in roots. To investigate the specific functions of the two isogenes Gln-1;1 and Gln-1;2 in shoots for ammonium detoxification, single and double knock-out mutants were grown under standard N supply or with high ammonium provision. Phenotypes of the single mutant gln1;1 were similar to the wild type, while growth of the gln1;2 single mutant and the gln1;1:gln1;2 double mutant was significantly impaired irrespective of N regime. GS1 activity was significantly reduced in both gln1;2 and gln1;1:gln1;2. Along with this, the ammonium content increased while that of Gln decreased, showing that Gln-1;2 was essential for ammonium assimilation and amino acid synthesis. We conclude that Gln-1;2 is the main isozyme contributing to shoot GS1 activity in vegetative growth stages and can be up-regulated to relieve ammonium toxicity. This reveals, to our knowledge, a novel shoot function of Gln-1;2 in Arabidopsis shoots.

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Section: Discussionmentioning

confidence: 70%

Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity

et al. 2016

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“…Thus, it has been suggested that GS2 could assimilate the ammonium derived from photorespiration (Wallsgrove et al , 1987), whereas GS1 isozymes assimilate non-photorespiratory ammonium (Tobin and Yamaya, 2001). In addition to primary uptake and photorespiration, ammonium can originate in several metabolic processes, including nitrate reduction, phenylpropanoid metabolism, degradation of transported amides, and protein catabolism (Schjoerring et al , 2002; Li et al , 2014). Four GS1 isozymes of Arabidopsis, encoded by GLN1;1 , GLN1;2 , GLN1;3 , and GLN1;4 , have been identified to have different enzymatic characteristics when they are expressed in E. coli (Ishiyama et al , 2004).…”

Section: Introductionmentioning

confidence: 99%

Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots

Konishi

Ishiyama

Beier

et al. 2016

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100

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“…Most plants display a clear preference for one form of inorganic nitrogen, though substantial differences can exist among cultivars/ecotypes of a single species (Boudsocq et al, 2012;Sarasketa et al, 2014). Although ammonium requires less reductant to assimilate, nitrate is the preferred nitrogen source for many crop species, and the provision of ammonium as the sole source of nitrogen can be toxic (Britto and Kronzucker, 2002;Li et al, 2014). From a physiological perspective, nitrate nutrition is associated with elevated cytokinin biosynthesis, increased organic acid content, and soil alkalinization, while ammonium nutrition is associated with increased activity of alternative respiratory pathways, elevated amino acid content, and soil acidification (Walch-Liu et al, 2005;Patterson et al, 2010).…”

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confidence: 99%

Nitrate-Regulated Glutaredoxins Control Arabidopsis Primary Root Growth

et al. 2015

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Nitrogen is an essential soil nutrient for plants, and lack of nitrogen commonly limits plant growth. Soil nitrogen is typically available to plants in two inorganic forms: nitrate and ammonium. To better understand how nitrate and ammonium differentially affect plant metabolism and development, we performed transcriptional profiling of the shoots of ammoniumsupplied and nitrate-supplied Arabidopsis (Arabidopsis thaliana) plants. Seven genes encoding class III glutaredoxins were found to be strongly and specifically induced by nitrate. RNA silencing of four of these glutaredoxin genes (AtGRXS3/4/5/8) resulted in plants with increased primary root length (approximately 25% longer than the wild type) and decreased sensitivity to nitratemediated inhibition of primary root growth. Increased primary root growth is also a well-characterized phenotype of many cytokinin-deficient plant lines. We determined that nitrate induction of glutaredoxin gene expression was dependent upon cytokinin signaling and that cytokinins could activate glutaredoxin gene expression independent of plant nitrate status. In addition, crosses between "long-root" cytokinin-deficient plants and "long-root" glutaredoxin-silenced plants generated hybrids that displayed no further increase in primary root length (i.e. epistasis). Collectively, these findings suggest that AtGRXS3/4/5/8 operate downstream of cytokinins in a signal transduction pathway that negatively regulates plant primary root growth in response to nitrate. This pathway could allow Arabidopsis to actively discriminate between different nitrogen sources in the soil, with the preferred nitrogen source, nitrate, acting to suppress primary root growth (vertical dimension) in concert with its well-characterized stimulatory effect on lateral root growth (horizontal dimension).

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Ammonium stress in Arabidopsis: signaling, genetic loci, and physiological targets

Cited by 220 publications

References 79 publications

Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity

Cytosolic Glutamine Synthetase Gln1;2 Is the Main Isozyme Contributing to GS1 Activity and Can Be Up-Regulated to Relieve Ammonium Toxicity

Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots

Nitrate-Regulated Glutaredoxins Control Arabidopsis Primary Root Growth

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