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Ammonium

The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

Nicolaus Von Wiren – 1st expert on this subject based on the ideXlab platform

  • Ammonium as a signal for physiological and morphological responses in plants
    Journal of Experimental Botany, 2017
    Co-Authors: Nicolaus Von Wiren

    Abstract:

    Ammonium is a major inorganic nitrogen source for plants. At low external supplies, Ammonium promotes plant growth, while at high external supplies it causes toxicity. Ammonium triggers rapid changes in cytosolic pH, in gene expression, and in post-translational modifications of proteins, leading to apoplastic acidification, co-ordinated Ammonium uptake, enhanced Ammonium assimilation, altered oxidative and phytohormonal status, and reshaped root system architecture. Some of these responses are dependent on AMT-type Ammonium transporters and are not linked to a nutritional effect, indicating that Ammonium is perceived as a signaling molecule by plant cells. This review summarizes current knowledge of Ammonium-triggered physiological and morphological responses and highlights existing and putative mechanisms mediating Ammonium signaling and sensing events in plants. We put forward the hypothesis that sensing of Ammonium takes place at multiple steps along its transport, storage, and assimilation pathways.

  • feedback inhibition of Ammonium uptake by a phospho dependent allosteric mechanism in arabidopsis
    The Plant Cell, 2009
    Co-Authors: Viviane Lanquar, Nicolaus Von Wiren, Dominique Loque, Friederike Hormann, Lixing Yuan, Anne Bohner, Wolfgang R Engelsberger, Sylvie Lalonde, Waltraud X Schulze, Wolf B Frommer

    Abstract:

    The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for Ammonium acquisition in bacteria, fungi, and plants. The Ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive interaction between a trimer of subunits for function. Allosteric regulation is mediated by a cytosolic C-terminal trans-activation domain, which carries a conserved Thr (T460) in a critical position in the hinge region of the C terminus. When expressed in yeast, mutation of T460 leads to inactivation of the trimeric complex. This study shows that phosphorylation of T460 is triggered by Ammonium in a time- and concentration-dependent manner. Neither Gln nor l-methionine sulfoximine–induced Ammonium accumulation were effective in inducing phosphorylation, suggesting that roots use either the Ammonium transporter itself or another extracellular sensor to measure Ammonium concentrations in the rhizosphere. Phosphorylation of T460 in response to an increase in external Ammonium correlates with inhibition of Ammonium uptake into Arabidopsis roots. Thus, phosphorylation appears to function in a feedback loop restricting Ammonium uptake. This novel autoregulatory mechanism is capable of tuning uptake capacity over a wide range of supply levels using an extracellular sensory system, potentially mediated by a transceptor (i.e., transporter and receptor).

Wolf B Frommer – 2nd expert on this subject based on the ideXlab platform

  • feedback inhibition of Ammonium uptake by a phospho dependent allosteric mechanism in arabidopsis
    The Plant Cell, 2009
    Co-Authors: Viviane Lanquar, Nicolaus Von Wiren, Dominique Loque, Friederike Hormann, Lixing Yuan, Anne Bohner, Wolfgang R Engelsberger, Sylvie Lalonde, Waltraud X Schulze, Wolf B Frommer

    Abstract:

    The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for Ammonium acquisition in bacteria, fungi, and plants. The Ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive interaction between a trimer of subunits for function. Allosteric regulation is mediated by a cytosolic C-terminal trans-activation domain, which carries a conserved Thr (T460) in a critical position in the hinge region of the C terminus. When expressed in yeast, mutation of T460 leads to inactivation of the trimeric complex. This study shows that phosphorylation of T460 is triggered by Ammonium in a time- and concentration-dependent manner. Neither Gln nor l-methionine sulfoximine–induced Ammonium accumulation were effective in inducing phosphorylation, suggesting that roots use either the Ammonium transporter itself or another extracellular sensor to measure Ammonium concentrations in the rhizosphere. Phosphorylation of T460 in response to an increase in external Ammonium correlates with inhibition of Ammonium uptake into Arabidopsis roots. Thus, phosphorylation appears to function in a feedback loop restricting Ammonium uptake. This novel autoregulatory mechanism is capable of tuning uptake capacity over a wide range of supply levels using an extracellular sensory system, potentially mediated by a transceptor (i.e., transporter and receptor).

Yi Zhang – 3rd expert on this subject based on the ideXlab platform

  • adsorption mechanisms of high levels of Ammonium onto natural and nacl modified zeolites
    Separation and Purification Technology, 2013
    Co-Authors: Li Wang, Yi Zhang

    Abstract:

    Abstract Zeolites, microporous aluminosilicate minerals, have high affinity to Ammonium in water. This study explored the mechanisms of Ammonium adsorption onto natural zeolite and NaCl-modified counterpart under different Ammonium levels (10–4000 mg-N/L) and initial pH 3.4–11.1. Ion exchange dominated the Ammonium adsorption process near neutral pH, with the order of exchange selectivity following Na +  > Ca 2+  > K +  > Mg 2+ . At high Ammonium levels, Ca 2+ exceeded Na + as the dominant ions for Ammonium adsorption. Conversely, in strong alkaline solutions, molecular adsorption suppressed ion exchange in Ammonium adsorption. NaCl modification effectively increased Ammonium adsorption capacity by increasing the Na contents in zeolite and by modifying the surface morphology to enhance film mass transfer rate. The modified zeolite presents a potential adsorbent to reduce Ammonium concentration in landfill leachates, livestock wastewaters or effluents from anaerobic digestion tanks of livestock manure.