title: TRH1 encodes a potassium transporter required for tip growth in Arabidopsis root hairs.
abstract: Root hair initiation involves the formation of a bulge at the basal end of the trichoblast by localized diffuse growth. Tip growth occurs subsequently at this initiation site and is accompanied by the establishment of a polarized cytoplasmic organization. Arabidopsis plants homozygous for a complete loss-of-function tiny root hair 1 (trh1) mutation were generated by means of the T-DNA-tagging method. Trichoblasts of trh1 plants form initiation sites but fail to undergo tip growth. A predicted primary structure of TRH1 indicates that it belongs to the AtKT/AtKUP/HAK K(+) transporter family. The proposed function of TRH1 as a K(+) transporter was confirmed in (86)Rb uptake experiments, which demonstrated that trh1 plants are partially impaired in K(+) transport. In line with these results, TRH1 was able to complement the trk1 potassium transporter mutant of Saccharomyces, which is defective in high-affinity K(+) uptake. Surprisingly, the trh1 phenotype was not restored when mutant seedlings were grown at high external potassium concentrations. These data demonstrate that TRH1 mediates K(+) transport in Arabidopsis roots and is responsible for specific K(+) translocation, which is essential for root hair elongation.
authors.affiliation: Laboratory of Molecular Biology, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: S
authors.initials: S
authors.lastname: Rigas
authors.forename: G
authors.initials: G
authors.lastname: Debrosses
authors.forename: K
authors.initials: K
authors.lastname: Haralampidis
authors.forename: F
authors.initials: F
authors.lastname: Vicente-Agullo
authors.forename: K A
authors.initials: KA
authors.lastname: Feldmann
authors.forename: A
authors.initials: A
authors.lastname: Grabov
authors.forename: L
authors.initials: L
authors.lastname: Dolan
authors.forename: P
authors.initials: P
authors.lastname: Hatzopoulos
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017343:Genes, Plant; D005816:Genetic Complementation Test; D017136:Ion Transport; D008969:Molecular Sequence Data; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D011188:Potassium