K+ channels of stomatal guard cells: Abscisic-acid-evoked control of the outward rectifier mediated by cytoplasmic pH

Planta ◽  
1993 ◽  
Vol 191 (3) ◽  
Author(s):  
MichaelR. Blatt ◽  
Fiona Armstrong
Keyword(s):  
Abscisic Acid ◽  
Guard Cells ◽  
Cytoplasmic Ph ◽  
K Channels ◽  
Stomatal Guard Cells

scholarly journals K+ channels of stomatal guard cells. Characteristics of the inward rectifier and its control by pH.

1992 ◽  
Vol 99 (4) ◽  
pp. 615-644 ◽  
Author(s):  
M R Blatt
Keyword(s):  
Intracellular Ph ◽  
Guard Cells ◽  
Inward Rectifier ◽  
Equilibrium Potential ◽  
Egg Cell ◽  
K Channels ◽  
Inward Rectifiers ◽  
Stomatal Guard Cells ◽  
K Current ◽  
Current Reversal

Intracellular microelectrode recordings and a two-electrode voltage clamp have been used to characterize the current carried by inward rectifying K+ channels of stomatal guard cells from the broadbean, Vicia faba L. Superficially, the current displayed many features common to inward rectifiers of neuromuscular and egg cell membranes. In millimolar external K+ concentrations (Ko+), it activated on hyperpolarization with half-times of 100-200 ms, showed no evidence of time- or voltage-dependent inactivation, and deactivated rapidly (tau approximately 10 ms) on clamping to 0 mV. Steady-state conductance-voltage characteristics indicated an apparent gating charge of 1.3-1.6. Current reversal showed a Nernstian dependence on Ko+ over the range 3-30 mM, and the inward rectifier was found to be highly selective for K+ over other monovalent cations (K+ greater than Rb+ greater than Cs+ much greater than Na+). Unlike the inward rectifiers of animal membranes, the current was blocked by charybdotoxin and alpha-dendrotoxin (Kd much less than 50 nM), as well as by tetraethylammonium chloride (K1/2 = 9.1 mM); gating of the guard cell K+ current was fixed to voltages near -120 mV, independent of Ko+, and the current activated only with supramillimolar K+ outside (EK+ greater than -120 mV). Most striking, however, was inward rectifier sensitivity to [H+] with the K+ current activated reversibly by mild acid external pH. Current through the K+ inward rectifier was found to be largely independent of intracellular pH and the current reversal (equilibrium) potential was unaffected by pHo from 7.4 to 5.5. By contrast, current through the K+ outward rectifier previously characterized in these cells (1988. J. Membr. Biol. 102:235) was largely insensitive to pHo, but was blocked reversibly by acid-going intracellular pH. The action of pHo on the K+ inward rectifier could not be mimicked by extracellular Ca2+ for which changes in activation, deactivation, and conductance were consonant with an effect on surface charge ([Ca2+] less than or equal to 1 mM). Rather, extracellular pH affected activation and deactivation kinetics disproportionately, with acid-going pHo raising the K+ conductance and shifting the conductance-voltage profile positive-going along the voltage axis and into the physiological voltage range. Voltage and pH dependencies for gating were consistent with a single, titratable group (pKa approximately 7 at -200 mV) residing deep within the membrane electric field and accessible from the outside.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of the inward K+-channels in stomatal guard cells by cytoskeletal microtubules

1999 ◽  
Vol 44 (10) ◽  
pp. 919-923 ◽  
Author(s):  
Ximing Zhou ◽  
Weihua Wu ◽  
Ming Yuan ◽  
Xuechen Wang
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Stomatal Guard Cells

Abscisic acid inhibition of potassium influx into stomatal guard cells

1972 ◽  
Vol 66 (3) ◽  
pp. 193-196 ◽  
Author(s):  
Roger F. Horton ◽  
Lyle Moran
Keyword(s):  
Abscisic Acid ◽  
Guard Cells ◽  
Acid Inhibition ◽  
Stomatal Guard Cells ◽  
Potassium Influx

Potassium channel currents in intact stomatal guard cells: rapid enhancement by abscisic acid

Planta ◽  
1990 ◽  
Vol 180 (3) ◽  
pp. 445-455 ◽  
Author(s):  
Michael R. Blatt
Keyword(s):  
Abscisic Acid ◽  
Potassium Channel ◽  
Guard Cells ◽  
Stomatal Guard Cells ◽  
Channel Currents

Effects of abscisic acid on potassium uptake and starch content of stomatal guard cells

Planta ◽  
1971 ◽  
Vol 101 (2) ◽  
pp. 147-158 ◽  
Author(s):  
T. A. Mansfield ◽  
Ruth J. Jones
Keyword(s):  
Abscisic Acid ◽  
Starch Content ◽  
Guard Cells ◽  
Potassium Uptake ◽  
Stomatal Guard Cells

scholarly journals Visualizing Changes in Cytosolic-Free Ca2+ during the Response of Stomatal Guard Cells to Abscisic Acid.

1992 ◽  
pp. 1113-1122 ◽  
Author(s):  
M. R. McAinsh ◽  
C. Brownlee ◽  
A. M. Hetherington
Keyword(s):  
Abscisic Acid ◽  
Guard Cells ◽  
Stomatal Guard Cells
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