Exploring ammonium tolerance in a large panel of Arabidopsis thaliana natural accessions

J Exp Bot. 2014 Nov;65(20):6023-33. doi: 10.1093/jxb/eru342. Epub 2014 Sep 9.

Abstract

Plants are dependent on exogenous nitrogen (N) supply. Ammonium (NH₄(+)), together with nitrate (NO₃(-)), is one of the main nitrogenous compounds available in the soil. Paradoxically, although NH4 (+) assimilation requires less energy than that of NO₃(-), many plants display toxicity symptoms when grown with NH₄(+) as the sole N source. However, in addition to species-specific ammonium toxicity, intraspecific variability has also been shown. Thus, the aim of this work was to study the intraspecific ammonium tolerance in a large panel of Arabidopsis thaliana natural accessions. Plants were grown with either 1mM NO₃(-) or NH₄(+) as the N source, and several parameters related to ammonium tolerance and assimilation were determined. Overall, high variability was observed in A. thaliana shoot growth under both forms of N nutrition. From the parameters determined, tissue ammonium content was the one with the highest impact on shoot biomass, and interestingly this was also the case when N was supplied as NO₃(-). Enzymes of nitrogen assimilation did not have an impact on A. thaliana biomass variation, but the N source affected their activity. Glutamate dehydrogenase (GDH) aminating activity was, in general, higher in NH4 (+)-fed plants. In contrast, GDH deaminating activity was higher in NO₃(-)-fed plants, suggesting a differential role for this enzyme as a function of the N form supplied. Overall, NH4 (+) accumulation seems to be an important player in Arabidopsis natural variability in ammonium tolerance rather than the cell NH₄(+) assimilation capacity.

Keywords: Ammonium; Arabidopsis thaliana; glutamate dehydrogenase; glutamine synthetase; natural variation; nitrate; nitrogen..

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ammonium Compounds / metabolism
  • Ammonium Compounds / toxicity*
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Genetic Variation*
  • Glutamate Dehydrogenase / genetics
  • Glutamate Dehydrogenase / metabolism
  • Glutamate-Ammonia Ligase / genetics
  • Glutamate-Ammonia Ligase / metabolism
  • Nitrates / metabolism*
  • Nitrogen / metabolism*
  • Plant Shoots / drug effects
  • Plant Shoots / genetics
  • Plant Shoots / growth & development
  • Plant Shoots / physiology

Substances

  • Ammonium Compounds
  • Arabidopsis Proteins
  • Nitrates
  • Glutamate Dehydrogenase
  • Glutamate-Ammonia Ligase
  • Nitrogen