Journal Article

Nucleotides and Mg<sup>2+</sup> Ions Differentially Regulate K<sup>+</sup> Channels and Non-Selective Cation Channels Present in Cells Forming the Stomatal Complex

Thomas Wolf, David Roger Guinot, Rainer Hedrich, Petra Dietrich and Irene Marten

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 10, pages 1682-1689
Published in print October 2005 | ISSN: 0032-0781
Published online October 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci184
Nucleotides and Mg2+ Ions Differentially Regulate K+ Channels and Non-Selective Cation Channels Present in Cells Forming the Stomatal Complex

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Voltage-dependent inward-rectifying (Kin) and outward-rectifying (Kout) K+ channels are capable of mediating K+ fluxes across the plasma membrane. Previous studies on guard cells or heterologously expressed K+ channels provided evidence for the requirement of ATP to maintain K+ channel activity. Here, the nucleotide and Mg2+ dependencies of time-dependent Kin and Kout channels from maize subsidiary cells were examined, showing that MgATP as well as MgADP function as channel activators. In addition to Kout channels, these studies revealed the presence of another outward-rectifying channel type (MgC) in the plasma membrane that however gates in a nucleotide-independent manner. MgC represents a new channel type distinguished from Kout channels by fast activation kinetics, inhibition by elevated intracellular Mg2+ concentration, permeability for K+ as well as for Na+ and insensitivity towards TEA+. Similar observations made for guard cells from Zea mays and Vicia faba suggest a conserved regulation of channel-mediated K+ and Na+ transport in both cell types and species.

Keywords: Guard cell; K+ channel; Mg2+; non-selective cation channel; Nucleotides; Subsidiary cell

Journal Article.  6021 words.  Illustrated.

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

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