title: Exploring ammonium tolerance in a large panel of Arabidopsis thaliana natural accessions.
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.
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain.
authors.forename: Asier
authors.initials: A
authors.lastname: Sarasketa
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain.
authors.forename: María Begoña
authors.initials: MB
authors.lastname: González-Moro
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: González-Murua
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Apdo. 644, E-48080 Bilbao, Spain Ikerbasque, Basque Foundation for Science, E-48011 Bilbao, Spain daniel.marino@ehu.es.
authors.forename: Daniel
authors.initials: D
authors.lastname: Marino
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism / Q000633:toxicity*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D014644:Genetic Variation; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology
chemical_list: D064751:Ammonium Compounds; D029681:Arabidopsis Proteins; D009566:Nitrates; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Ammonium; Arabidopsis thaliana; glutamate dehydrogenase; glutamine synthetase; natural variation; nitrate; nitrogen.