Salt Adaptation of K^+ Channels in the Plasma Membrane of Tobacco Cells in Suspension Culture : ENVIRONMENTAL AND STRESS RESPONSES : MEMBRANES AND BIOENERGETICS

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The patch-clamp technique was used to study and compare the characteristics of cation channels in the plasma membrane of cultured lines of tobacco (Nicotiana tabacum L. cv. Bright Yellow-2) cells that were unadapted (NaCl^-unadapted cells) and adapted to 50 and 100 mM NaCl (Na 50-adapted and Na 100-adapted cells). In these three types of tobacco cell, the outward whole-cell current activated by depolarization was dominated mainly by the activity of the outward rectifying K^+ channels with a single-channel conductance of 20 pS. The steady-state amplitude of the outward whole-cell currents at all the positive potentials examined decreased in the following order: NaCl^-unadapted cells > Na 50-adapted cells > Na 100-adapted cells. There were no significant differences between the NaCl^-unadapted and the Na 50-adapted cells in terms of the ratio of permeabilities of these channels to K^+ and Na^+ ions. Furthermore, no significant differences in terms of the single-channel conductance of these channels were observed among the NaCl^-unadapted, the Na 50-adapted and the Na 100-adapted cells. These observations suggest that adaptation to salinity of tobacco cells in suspension results in reduced permeability of the K^+ channels to both K^+ and Na^+ ions, without any change in the K^+/Na^+ selectivity and single-channel conductance of these channels.
日本植物生理学会の論文