Mechanism of the chilling-induced decrease in proton pumping across the tonoplast of rice cells

Area of Science:

• Plant Physiology
• Membrane Biophysics
• Biochemistry

Background:

• Chilling stress significantly impacts plant cellular functions, particularly membrane transport.
• Tonoplast H+-ATPase activity is crucial for maintaining cellular homeostasis in plants.
• Understanding chilling sensitivity in crops like rice is vital for agricultural productivity.

Purpose of the Study:

• To investigate the effect of chilling on ATP-generated proton pumping in Boro rice tonoplast.
• To elucidate the role of membrane fluidity and lipid composition in chilling-induced functional decline.
• To identify the specific lipid components responsible for altered membrane properties under chilling stress.

Main Methods:

• Measurement of ATP-generated proton pumping across tonoplast vesicles.
• Assessment of membrane fluidity using fluorescence depolarization and electron spin resonance spectroscopy.
• Reconstitution of tonoplast H+-ATPase into liposomes with varying glycolipid content.

Main Results:

• Chilling at 5°C for 3 days markedly decreased proton pumping in Boro rice tonoplast vesicles.
• A decrease in the fluidity of the tonoplast lipid bilayer's surface region was observed after chilling.
• Reduced proton pumping correlated with increased glycolipid content and was dependent on tonoplast glycolipids from chilled cells.

Conclusions:

• The reduction in ATP-driven proton pumping by chilling is attributed to decreased tonoplast membrane fluidity.
• Changes in the composition or structure of glycolipids in the tonoplast surface region are responsible for reduced fluidity and impaired proton transport.
• These findings highlight the critical role of membrane lipid dynamics in chilling tolerance of Boro rice.