title: Ammonium transport and CitAMT1 expression are regulated by light and sucrose in Citrus plants.
abstract: Here the isolation and characterization of CitAMT1 cDNA from citrange Troyer (Citrus sinensis L. OsbeckxPoncirus trifoliata Blanco) is reported, suggesting that this belongs to the AMT gene family, which is involved in the high-affinity transport system (HATS). Results show that in Citrus plants, the HATS is much more dependent on the light conditions and C status of the roots than the low-affinity transport system. Most importantly, a strong correlation was found between the regulation of both HATS activity and CitAMT1 expression. CitAMT1 expression is sucrose-stimulated and may account for the regulation of NH(4)(+) HATS. Furthermore, a similar link was also recorded with photosynthetic activity in the shoots, suggesting that the variations in production and transport of photosynthates to the roots are responsible for the diurnal changes of both CitAMT1 expression and NH(4)(+) HATS activity. On the other hand, results indicate that the effect of stimulating light on CitAMT1 expression and NH(4)(+) HATS activity is independent of the circadian rhythm. Finally, CitAMT1 expression seems to be specifically stimulated by sucrose, suggesting that sucrose is a pivotal signal governing both assimilate partitioning from source organs and assimilate utilization in sink organs.
authors.affiliation: Area de Fisiología Vegetal, Departamento de Ciencias Agrarias y del Medio Natural, Escuela Superior de Tecnología y Ciencias Experimentales, Universitat Jaume I, E-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; D032084:Citrus sinensis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018076:DNA, Complementary / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008027:Light; D010788:Photosynthesis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D013395:Sucrose