Mechanism of high-affinity potassium uptake in roots of Arabidopsis thaliana

Potassium is a major nutrient in higher plants, where it plays a role in turgor regulation, charge balance, leaf movement, and protein synthesis. Terrestrial plants are able to sustain growth at micromolar external K+ concentrations, at which K+ uptake across the plasma membrane of root cells must b...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1994-09, Vol.91 (20), p.9272-9276
Main Authors: Maathuis, F.J.M, Sanders, D
Format: Article
Language:English
Subjects:
ABSORCION DE SUSTANCIAS NUTRITIVAS
ABSORPTION DE SUBSTANCES NUTRITIVES
Arabidopsis - physiology
ARABIDOPSIS THALIANA
Biological Transport
CATION
CATIONES
Cell membranes
Cellular biology
Depolarization
Electrodes
Epidermal cells
EPIDERME
EPIDERMIS
ESTRUCTURA CELULAR
Flowers & plants
HIDROGENO
Hydrogen
HYDROGENE
ION
IONES
Kinetics
MEMBRANA
MEMBRANE
Membrane potential
Membrane Potentials - drug effects
MINERALES
MINERAUX
Plant roots
Plant Roots - physiology
Plants
POTASIO
POTASSIUM
Potassium - metabolism
Potassium - pharmacology
Protons
PROTOPLASTE
PROTOPLASTOS
Protoplasts
Protoplasts - physiology
RACINE
RAICES
STRUCTURE CELLULAIRE
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Summary:Potassium is a major nutrient in higher plants, where it plays a role in turgor regulation, charge balance, leaf movement, and protein synthesis. Terrestrial plants are able to sustain growth at micromolar external K+ concentrations, at which K+ uptake across the plasma membrane of root cells must be energized despite the presence of a highly negative membrane potential. However, the mechanism of energization has long remained obscure. Therefore, whole. cell mode patch clamping has been applied to root protoplasts from Arabidopsis thaliana to characterize membrane currents resulting from the application of micromolar K+. Analysis of whole cell current/voltage relationships in the presence and absence of micromolar K+ enabled direct testing of K+ transport for possible energization by cytoplasmic ATP and the respective trans-membrane gradients of Na+, Ca2+, and H+. Subtracted current/voltage relations for K+-dependent membrane currents are independent of ATP and reverse at potentials that imply H+-coupled K+ transport with a ratio of 1 H+:K+. Furthermore, the reversal potential of the K+ current shifts negative as external H+ activity is decreased. K+-dependent currents saturate in the micromolar concentration range with an apparent Km of 30 micromolar, a value in dose agreement with previously reported Km values for high-affinity K+ uptake. We conclude that our results are consistent with the view that high-affinity K+ uptake in higher plants is mediated by a H+:K+ symport mechanism, competent in driving K+ accumulation to udibrium ratios in excess of 106-fold
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.91.20.9272