Relative contribution of AtHAK5 and AtAKT1 to K+ uptake in the high-affinity range of concentrations

Physiol Plant. 2008 Dec;134(4):598-608. doi: 10.1111/j.1399-3054.2008.01168.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Barium Compounds / metabolism
  • Barium Compounds / pharmacology
  • Biological Transport
  • Chlorides / metabolism
  • Chlorides / pharmacology
  • DNA, Bacterial / genetics
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Mutagenesis, Insertional
  • Mutation
  • Plant Roots / genetics
  • Plant Roots / metabolism
  • Potassium / metabolism*
  • Potassium Channels / genetics
  • Potassium Channels / metabolism*
  • Potassium-Hydrogen Antiporters
  • Quaternary Ammonium Compounds / metabolism
  • RNA, Plant / genetics
  • Rubidium / metabolism
  • Rubidium / pharmacology
  • Symporters / genetics
  • Symporters / metabolism*

Substances

  • Arabidopsis Proteins
  • Barium Compounds
  • Chlorides
  • DNA, Bacterial
  • Potassium Channels
  • Potassium-Hydrogen Antiporters
  • Quaternary Ammonium Compounds
  • RNA, Plant
  • Symporters
  • T-DNA
  • potassium transporter, Arabidopsis
  • barium chloride
  • AKT1 protein, Arabidopsis
  • Rubidium
  • rubidium chloride
  • Potassium