title: Plant nitrogen assimilation and its regulation: a complex puzzle with missing pieces.
abstract: Nitrogen (N) is an essential element for plants that is available in agricultural soils mainly as macronutrients in the form of nitrate and ammonium. Interplay between high-affinity and low-affinity transporters ensures efficient uptake from the soil even under highly fluctuating N availability. After uptake, N assimilation comprises the reduction of nitrate to ammonium and its subsequent incorporation into amino acids. Amino acids, but also nitrate, are transported from root to shoot and vice versa. Most steps of N transport and assimilation are tightly controlled by a regulatory network acting both cell-autonomously and systemically. N sensors, transcription factors and further regulatory players have been identified during recent years, elucidating parts of the huge puzzle that represents the efficient use of N by plants.
authors.affiliation: Institut National de la Recherche Agronomique (INRA), UMR1318, Institut Jean-Pierre Bourgin, Saclay Plant Sciences, RD10, F-78000 Versailles, France; AgroParisTech, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France. Electronic address: anne.krapp@versailles.inra.fr.
authors.forename: Anne
authors.initials: A
authors.lastname: Krapp
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D064751:Ammonium Compounds / Q000378:metabolism*; D001692:Biological Transport; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D064751:Ammonium Compounds; D009566:Nitrates; D012987:Soil; D009584:Nitrogen