Mechanisms of fusicoccin action: kinetic modification and inactivation of K+ channels in guard cells

Planta ◽  
1989 ◽  
Vol 178 (4) ◽  
pp. 509-523 ◽  
Author(s):  
Michael R. Blatt ◽  
Gill M. Clint
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Fusicoccin Action

Electrophysiological Identification and Activity Analyses of Plasma Membrane K+ Channels in Maize Guard Cells

2018 ◽  
Vol 60 (4) ◽  
pp. 765-777
Author(s):  
Yong-Qiang Gao ◽  
Wei-Hua Wu ◽  
Yi Wang
Keyword(s):  
Plasma Membrane ◽  
Guard Cells ◽  
K Channels

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

scholarly journals Inward-rectifying K+ channels in guard cells provide a mechanism for low-affinity K+ uptake.

1991 ◽  
Vol 88 (24) ◽  
pp. 11583-11587 ◽  
Author(s):  
J. I. Schroeder ◽  
H. H. Fang
Keyword(s):  
Guard Cells ◽  
K Uptake ◽  
K Channels

Voltage-Dependent K + Channels as Targets of Osmosensing in Guard Cells

1998 ◽  
Vol 10 (11) ◽  
pp. 1957 ◽  
Author(s):  
Kun Liu ◽  
Sheng Luan
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Voltage Dependent

scholarly journals K+ transport properties of K+ channels in the plasma membrane of Vicia faba guard cells.

1988 ◽  
Vol 92 (5) ◽  
pp. 667-683 ◽  
Author(s):  
J I Schroeder
Keyword(s):  
Plasma Membrane ◽  
Transport Properties ◽  
Vicia Faba ◽  
Guard Cell ◽  
Guard Cells ◽  
Stomatal Opening ◽  
Whole Cell ◽  
K Channels ◽  
K Transport ◽  
K Currents

Electrical properties of the plasma membrane of guard cell protoplasts isolated from stomates of Vicia faba leaves were studied by application of the whole-cell configuration of the patch-clamp technique. The two types of K+ currents that have recently been identified in guard cells may allow efflux of K+ during stomatal closing, and uptake of K+ during stomatal opening (Schroeder et al., 1987). A detailed characterization of ion transport properties of the inward-rectifying (IK+,in) and the outward-rectifying (IK+,out) K+ conductance is presented here. The permeability ratios of IK+,in and IK+,out currents for K+ over monovalent alkali metal ions were determined. The resulting permeability sequences (PK+ greater than PRb+ greater than PNa+ greater than PLi+ much greater than PCs+) corresponded closely to the ion specificity of guard cell movements in V. faba. Neither K+ currents exhibited significant inactivation when K+ channels were activated for prolonged periods (greater than 10 min). The absence of inactivation may permit long durations of K+ fluxes, which occur during guard cell movements. Activation potentials of inward K+ currents were not shifted when external K+ concentrations were changed. This differs strongly from the behavior of inward-rectifying K+ channels in animal tissue. Blue light and fusicoccin induce hyperpolarization by stimulation of an electrogenic pump. From slow-whole-cell recordings it was concluded that electrogenic pumps require cytoplasmic substrates for full activation and that the magnitude of the pump current is sufficient to drive K+ uptake through IK+,in channels. First, direct evidence was gained for the hypothesis that IK+,in channels are a molecular pathway for K+ accumulation by the finding that IK+,in was blocked by Al3+ ions, which are known to inhibit stomatal opening but not closing. The results presented in this study strongly support a prominent role for IK+,in and IK+,out channels in K+ transport across the plasma membrane of guard cells.

scholarly journals Voltage-Dependent K+ Channels as Targets of Osmosensing in Guard Cells

1998 ◽  
Vol 10 (11) ◽  
pp. 1957-1970 ◽  
Author(s):  
Kun Liu ◽  
Sheng Luan
Keyword(s):  
Guard Cells ◽  
K Channels ◽  
Voltage Dependent

Differential expression of K+ channels between guard cells and subsidiary cells within the maize stomatal complex

Planta ◽  
2005 ◽  
Vol 222 (6) ◽  
pp. 968-976 ◽  
Author(s):  
Kai Büchsenschütz ◽  
Irene Marten ◽  
Dirk Becker ◽  
Katrin Philippar ◽  
Peter Ache ◽  
...  
Keyword(s):  
Differential Expression ◽  
Guard Cells ◽  
Stomatal Complex ◽  
K Channels ◽  
Subsidiary Cells

scholarly journals K+ channels of stomatal guard cells: bimodal control of the K+ inward-rectifier evoked by auxin

1994 ◽  
Vol 5 (1) ◽  
pp. 55-68 ◽  
Author(s):  
Michael R. Blatt ◽  
Gerhard Thiel
Keyword(s):  
Guard Cells ◽  
Inward Rectifier ◽  
K Channels ◽  
Stomatal Guard Cells

scholarly journals AKT2/3 Subunits Render Guard Cell K+ Channels Ca2+ Sensitive

2005 ◽  
Vol 125 (5) ◽  
pp. 483-492 ◽  
Author(s):  
Natalya Ivashikina ◽  
Rosalia Deeken ◽  
Susanne Fischer ◽  
Peter Ache ◽  
Rainer Hedrich
Keyword(s):  
Guard Cell ◽  
Guard Cells ◽  
Inward Rectifier ◽  
Hek293 Cells ◽  
K Channel ◽  
Dependent Manner ◽  
Wild Type ◽  
K Channels ◽  
Isolation And Characterization ◽  
Voltage Dependent

Inward-rectifying K+ channels serve as a major pathway for Ca2+-sensitive K+ influx into guard cells. Arabidopsis thaliana guard cell inward-rectifying K+ channels are assembled from multiple K+ channel subunits. Following the recent isolation and characterization of an akt2/3-1 knockout mutant, we examined whether the AKT2/3 subunit carries the Ca2+ sensitivity of the guard cell inward rectifier. Quantification of RT-PCR products showed that despite the absence of AKT2 transcripts in guard cells of the knockout plant, expression levels of the other K+ channel subunits (KAT1, KAT2, AKT1, and AtKC1) remained largely unaffected. Patch-clamp experiments with guard cell protoplasts from wild type and akt2/3-1 mutant, however, revealed pronounced differences in Ca2+ sensitivity of the K+ inward rectifier. Wild-type channels were blocked by extracellular Ca2+ in a concentration- and voltage-dependent manner. Akt2/3-1 mutants lacked the voltage-dependent Ca2+ block, characteristic for the K+ inward rectifier. To confirm the akt2/3-1 phenotype, two independent knockout mutants, akt2-1 and akt2::En-1 were tested, demonstrating that the loss of AKT2/3 indeed affects the Ca2+ dependence of guard cell inward rectifier. In contrast to AKT2 knockout plants, AKT1, AtKC1, and KAT1 loss-of-function mutants retained Ca2+ block of the guard cell inward rectifier. When expressed in HEK293 cells, AKT2 channel displayed a pronounced susceptibility toward extracellular Ca2+, while the dominant guard cell K+ channel KAT2 was Ca2+ insensitive. Thus, we conclude that the AKT2/3 subunit constitutes the Ca2+ sensitivity of the guard cell K+ uptake channel.

Sign in / Sign up

Export Citation Format

Share Document