title: Ammonium transport and CitAMT1 expression are regulated by N in Citrus plants.
abstract: Citrus seedlings (Citrus sinensis L. Osbeck x Poncirus trifoliata Blanco) were used to describe the effects of different N treatments on the NH4+ influx mediated by high- and low-affinity transport systems (HATS and LATS, respectively) and CitAMT1 gene expression. Results show that Citrus plants favor NH4+ over NO3- influx mediated by HATS and LATS when both N sources are present in the nutrient solution and Citrus plants display a much higher capacity to take up NH4+ than NO3-. Furthermore, NH4+ exerts a regulatory effect on NH4+ HATS activity and CitAMT1 expression, both are down-regulated by high N status of the plant, but specifically stimulated by NH4+ and the balance between these two opposite effects depends on the prior nutrition regime of the plant. On the other hand, supply of NO3- inhibits CitAMT1 expression but doesn't affect NH4+ HATS activity on the roots. To explain this discrepancy, it is possible that other CitAMT1 transporters, up-regulated by N limitation, but not repressed by NO3- could be involved in the stimulation of NH4+ HATS activity under pure NO3- nutrition or CitAMT1 transporter could be regulated at the post-transcriptional level.
authors.affiliation: Laboratorio de Bioquímica y Biotecnología, Area de Fisiología Vegetal, Departamento de Ciencias Agrarias y del Medio Natural, Escuela Superior de Tecnología y Ciencias Experimentales, Universitat Jaume I, 12071, Castellón de la Plana, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Camañes
authors.forename: Miguel
authors.initials: M
authors.lastname: Cerezo
authors.forename: Eduardo
authors.initials: E
authors.lastname: Primo-Millo
authors.forename: Alain
authors.initials: A
authors.lastname: Gojon
authors.forename: Pilar
authors.initials: P
authors.lastname: García-Agustín
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002957:Citrus / Q000187:drug effects* / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D007700:Kinetics; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000494:pharmacology*; D009928:Organ Specificity / Q000187:drug effects; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012996:Solutions
chemical_list: D009566:Nitrates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D009584:Nitrogen