AtKUP1: an Arabidopsis gene encoding high-affinity potassium transport activity

• Published in: The Plant cell 1998-01, Vol.10 (1), p.51-62
• Main Authors: Kim, E.J, Kwak, J.M, Uozumi, N, Schroeder, J.I
• Format: Article
• Language: English
• Subjects: ADN; Amino Acid Sequence; AMINO ACID SEQUENCES; Animals; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins; ARABIDOPSIS THALIANA; ARN MENSAJERO; ARN MESSAGER; Biological Transport; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cation Transport Proteins; CELL CULTURE; CELL MEMBRANES; CELL SUSPENSIONS; CHEMICAL COMPOSITION; COMPLEMENTARY DNA; COMPLEMENTATION; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; CULTIVO DE CELULAS; CULTURE DE CELLULE; Cultured cells; DNA; DNA, Complementary; ESCHERICHIA COLI; Escherichia coli - genetics; EXPRESION GENICA; EXPRESSION DES GENES; GENBANK/AF029876; GENE; GENE EXPRESSION; GENES; Genes, Plant; Genetic Complementation Test; GENETIC TRANSFORMATION; GENETICA; GENETICS; GENETIQUE; ION; ION TRANSPORT; ION UPTAKE; IONES; IONS; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; MESSENGER RNA; Models, Molecular; MOLECULAR SEQUENCE DATA; MULTIGENE FAMILIES; Multigene Family; MUTANT; MUTANTES; MUTANTS; Mutation; NUCLEOTIDE SEQUENCE; Oocytes; Plant cells; PLANT PROTEINS; Plant Proteins - genetics; Plant Proteins - metabolism; Plant roots; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; Plants; Plants, Genetically Modified; PLASMA MEMBRANES; POTASIO; POTASSIUM; Potassium - metabolism; Protein Conformation; PROTEINAS; PROTEINE; PROTEINS; Recombinant Proteins - metabolism; RNA; RUBIDIO; RUBIDIUM; Rubidium - metabolism; SACCHAROMYCES CEREVISIAE; SECUENCIA NUCLEOTIDICA; Sequence Homology, Amino Acid; SEQUENCE NUCLEOTIDIQUE; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; TRANSGENIC PLANTS; Xenopus; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.10.1.51

Because plants grow under many different types of soil and environmental conditions, we investigated the hypothesis that multiple pathways for K+ uptake exist in plants. We have identified a new family of potassium transporters from Arabidopsis by searching for homologous sequences among the expressed sequence tags of the GenBank database. The deduced amino acid sequences of AtKUP (for Arabidopsis thaliana K+ uptake transporter) cDNAs are highly homologous to the non-plant Kup and HAK1 potassium transporters from Escherichia coli and Schwanniomyces occidentalis, respectively. Interestingly, AtKUP1 and AtKUP2 are able to complement the potassium transport deficiency of an E. coli triple mutant. In addition, transgenic Arabidopsis suspension cells overexpressing AtKUP1 showed increased Rb+ uptake at micromolar concentrations with an apparent Km of approximately 22 micromolars, indicating that AtKUP1 encodes a high-affinity potassium uptake activity in vivo. A small, low-affinity Rb+ uptake component was also detected in AtKUP1-expressing cells. RNA gel blot analysis showed that the various members of the AtKUP family have distinct patterns of expression, with AtKUP3 transcript levels being strongly induced by K+ starvation. It is proposed that plants contain multiple potassium transporters for high-affinity uptake and that the AtKUP family may provide important components of high- and low-affinity K+ nutrition and uptake into various plant cell types