K+-Selective inward-rectifying channels and apoplastic pH in barley roots

Area of Science:

• Plant physiology
• Ion channel biophysics

Background:

• K+-selective inward-rectifying channels (KIRCs) show varied responses to external protons.
• Understanding KIRCs' apoplastic pH response in plant tissues is crucial.
• Previous studies focused on guard cells; root tissue responses remain largely uncharacterized.

Purpose of the Study:

• To investigate the effects of apoplastic pH on KIRCs in barley (Hordeum vulgare) roots.
• To characterize the KIRC activity in root cells under varying pH conditions.
• To link KIRC function in roots to proton-translocating systems.

Main Methods:

• Patch-clamp electrophysiology on barley root protoplasts.
• In planta characterization of apoplastic pH effects.
• Fluorescent dye measurements of barley root cell wall pH.
• Analysis of KIRC activation potentials and conductances.

Main Results:

• Decreased external pH shifted KIRC half-activation potential to more positive voltages.
• External acidification increased KIRC limit conductance, enhancing K+ uptake.
• Barley root KIRC activity resembles AKT1-type channels.
• Apoplastic pH in barley roots is near KIRC pK values and acidifies with fusicoccin.

Conclusions:

• Apoplastic pH significantly influences KIRC activity in barley roots.
• Root KIRC function is modulated by external acidity, similar to AKT1 channels.
• K+ uptake via KIRCs may be regulated by proton-translocating systems, impacting root development and stress responses.