title: Ammonium as a signal for physiological and morphological responses in plants.
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.
authors.affiliation: Molecular Plant Nutrition, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Stadt Seeland, OT Gatersleben, Germany.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Molecular Plant Nutrition, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Stadt Seeland, OT Gatersleben, Germany.
authors.forename: Nicolaus
authors.initials: N
authors.lastname: von Wirén
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D018517:Plant Roots / Q000033:anatomy & histology / Q000502:physiology; D010944:Plants / Q000033:anatomy & histology*; D015398:Signal Transduction
chemical_list: D064751:Ammonium Compounds
keywords: Membrane transporter; nitrogen signaling; nutrient sensing; root system architecture; signal transduction.