title: Relative contribution of AtHAK5 and AtAKT1 to K+ uptake in the high-affinity range of concentrations.
abstract: The relative contribution of the high-affinity K(+) transporter AtHAK5 and the inward rectifier K(+) channel AtAKT1 to K(+) uptake in the high-affinity range of concentrations was studied in Arabidopsis thaliana ecotype Columbia (Col-0). The results obtained with wild-type lines, with T-DNA insertion in both genes and specific uptake inhibitors, show that AtHAK5 and AtAKT1 mediate the NH4+-sensitive and the Ba(2+)-sensitive components of uptake, respectively, and that they are the two major contributors to uptake in the high-affinity range of Rb(+) concentrations. Using Rb(+) as a K(+) analogue, it was shown that AtHAK5 mediates absorption at lower Rb(+) concentrations than AtAKT1 and depletes external Rb(+) to values around 1 muM. Factors such as the presence of K(+) or NH4+ during plant growth determine the relative contribution of each system. The presence of NH4+ in the growth solution inhibits the induction of AtHAK5 by K(+) starvation. In K(+)-starved plants grown without NH4+, both systems are operative, but when NH4+ is present in the growth solution, AtAKT1 is probably the only system mediating Rb(+) absorption, and the capacity of the roots to deplete Rb(+) is reduced.
authors.affiliation: Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura-CSIC, Apartado de Correos 164, Murcia 30100, Spain. frubio@cebas.csic.es
authors.forename: Francisco
authors.initials: F
authors.lastname: Rubio
authors.forename: Manuel
authors.initials: M
authors.lastname: Nieves-Cordones
authors.forename: Fernando
authors.initials: F
authors.lastname: Alemán
authors.forename: Vicente
authors.initials: V
authors.lastname: Martínez
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D017609:Barium Compounds / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D016254:Mutagenesis, Insertional; D009154:Mutation; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D012413:Rubidium / Q000378:metabolism / Q000494:pharmacology; D027981:Symporters / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D017609:Barium Compounds; D002712:Chlorides; D004269:DNA, Bacterial; D015221:Potassium Channels; D027961:Potassium-Hydrogen Antiporters; D000644:Quaternary Ammonium Compounds; D018749:RNA, Plant; D027981:Symporters; C036483:T-DNA; C501258:potassium transporter, Arabidopsis; C024986:barium chloride; C074500:AKT1 protein, Arabidopsis; D012413:Rubidium; C032710:rubidium chloride; D011188:Potassium