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Identification and characterization of the inward K+ channel in the plasma membrane of Brassica pollen protoplasts
- Fan, L.M., Wu, W.H., Yang, H.Y.
- Plant & cell physiology 1999 v.40 no.8 pp. 859-865
- Brassica rapa subsp. chinensis, potassium, ion transport, protoplasts, pollen, electric current, cesium, sodium, barium, culture media, cytoplasm, cations, plasma membrane, application rate, inorganic ions, calcium
- 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 Ba(2+) 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 Ca(2+) concentrations from 10 nM to 30 micromolar or even 5 mM did not affect the inward K(+) currents. Decrease of external Ca(2+) concentrations from 10 mM to 1 mM inhibited the inward K(+) currents by 25%, while the increase of external Ca(2+) 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.