Journal Article

Identification and Characterization of the Inward K<sup>+</sup> Channel in the Plasma Membrane of <i>Brassica</i> Pollen Protoplasts

Liu-Min Fan, Wei-Hua Wu and Hong-Yuan Yang

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 8, pages 859-865
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029615
Identification and Characterization of the Inward K+ Channel in the Plasma Membrane of Brassica Pollen Protoplasts

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Patch clamp techniques have been used to identify and characterize the whole-cell currents carried by inward K+ channels in isolated matured pollen protoplasts of Brassica chinensis var. chinensis. The whole-cell inward currents in the isolated pollen protoplasts were activated at hyperpolarized membrane potentials more negative than −100 mV. The magnitudes of the whole-cell inward currents were strongly dependent on the external K+ concentration, and were highly selective for K over other monovalent cations. The inward currents were not observed when external K+ was replaced with the same concentration of Cs+ or Na+. The addition of 1 mM or 10 mM Ba2+ in external solutions resulted in 30% or 80% inhibition of the inward currents at −180 mV, respectively. These results demonstrated that the inward K+ currents mainly account for the recorded whole-cell inward currents in Brassica pollen protoplasts. Increase of cytoplasmic Ca2+ concentrations from 10 nM to 30 pM or even 5 μM did not affect the inward K+ currents. Decrease of external Ca2+ concentrations from 10 mM to 1 mM inhibited the inward K+ currents by 25%, while the increase of external Ca2+ from 10 mM to 50 mM almost completely blocked the inward K+ currents. Physiological importance of K+ transport into pollen and its possible regulatory mechanisms are also discussed.

Keywords: Brassica; Ca2+-regulation; Inward K+-channels; Patch clamp; Pollen protoplasts

Journal Article.  0 words. 

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

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