Details

Autor(en) / Beteiligte

• Spalding, E.P. (Yale University, New Haven, CT)
• Slayman, C.L
• Goldsmith, H.M
• Gradmann, D
• Bertl, A

Titel

Ion channels in Arabidopsis plasma membrane. Transport characteristics and involvement in light-induced voltage changes

Ist Teil von

• Plant physiology (Bethesda), 1992-05, Vol.99 (1), p.96-102

Ort / Verlag

Rockville, MD: American Society of Plant Physiologists

Erscheinungsjahr

1992

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• White light (25 watts per square meter) induced an increase in plasma membrane K+-channel activity and a 30- to 70-millivolt transient membrane depolarization (completed in 2-3 minutes) in Arabidopsis thaliana leaf mesophyll cells. Transport characteristics of three types of ion channels in the plasma membrane were determined using inside-out patches. With 220 millimolar K+ on the cytoplasmic side of the patch and 50 millimolar K+ in the pipette, (220/50 K), the open-channel current-voltage curves of these channels were sigmoidal and consistent with an enzyme kinetic model. Two channel types were selective for K+ over Na+ and Cl-. One (named PKC1) had a maximum conductance (Gmax) of 44 picosiemens at a membrane voltage (Vm) of -65 mV in (220/50 K) and is stimulated by light. The other (PKC2) had Gmax = 66 picosiemens at Vm = 60 millivolts in (220/50 K). The third channel type (PCC1) transported K+ and Na+ about equally well but not Cl(-). It had Gmax = 109 picosiemens at Vm = 55 millivolts in (250/50 K) with 10 millimolar Ca2+ on the cytoplasmic side. Reducing Ca2+ to 0.1 millimolar increased PCC1 open-channel currents by approximately 50% in a voltage-independent manner. Averaged over time, PKC2 and PCC1 currents strongly outward rectified and PKC1 currents did so weakly. Reductants (1 millimolar dithiothreitol or 10 millimolar beta-mercaptoethanol) added to the cytoplasmic side of an excised patch increased the open probability of all three channel types