Journal Article

Kinetic Analysis of the K<sup>+</sup>-Selective Outward Rectifier in <i>Arabidopsis</i> Mesophyll Cells: a Comparison with Other Plant Species

Hendrik Miedema, Lisa A. Romano and Sarah Assmann

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 2, pages 209-217
Published in print February 2000 | ISSN: 0032-0781
Published online February 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/41.2.209
Kinetic Analysis of the K+-Selective Outward Rectifier in Arabidopsis Mesophyll Cells: a Comparison with Other Plant Species

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This paper gives a kinetic analysis of the K+-selective outward-rectifier (IK,out) in the plasma membrane of Arabidopsis thaliana mesophyll cells in terms of the Hodgkin-Huxley formalism. We compared the kinetic characteristics of IK,out in Arabidopsis with IK,out channels in three other plant species that were subjected to a similar analysis: tobacco suspension cells, Vicia faba guard cells and Plantago media root cells. Because the activation kinetics of IK,out shows a clear voltage dependence, the time constant of half-activation (τ1/2) and the elementary rate constant of channel opening (α) were calculated at the potential of half-activation (V1/2). The Arabidopsis IK,out activates relatively slowly and this is reflected in a τ1/2 of approximately 1 s. The reason for this slow activation is twofold. Firstly, the value of α of 1.5 s−1 falls at the lower end of the range of values obtained for tobacco, Vicia and Plantago: 1.1 to 3.0 s−1. Secondly, IK,out in Arabidopsis has four closed states, while tobacco and Vicia have only two. As observed in other plant species, the activation kinetics of IK,out in Arabidopsis are sensitive to external K+: V1/2 shifts with EK but remains approximately 50 mV more positive than Kk

Keywords: Arabidopsis thaliana; Activation kinetics; Hodgkin-Huxley analysis; K+ outward rectifier; Mesophyll cell

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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