Ethylene Inhibited Plasma Membrane H⁺-ATPase to Decrease Root Na⁺ Efflux in Maize to Break Na⁺/H⁺ Homeostasis Under...

Area of Science:

• Plant Physiology
• Molecular Biology
• Agricultural Science

Background:

• Ethylene is crucial for plant growth and stress responses.
• Mechanisms of ethylene's regulation of sodium/hydrogen ion (Na+/H+) homeostasis and maize salt tolerance are not fully understood.
• ZmACO2, an ethylene biosynthesis gene, is induced by salt stress in maize.

Purpose of the Study:

• To investigate the role of ethylene in regulating Na+/H+ homeostasis in maize under salt stress.
• To elucidate the function of ZmACO2 in mediating maize salt tolerance.

Main Methods:

• Utilized ZmACO2-overexpressing (ACO2-OE) and mutant (aco2-cr) maize plants.
• Assessed Na+ and K+ ion accumulation and ratios in plant tissues.
• Measured gene expression levels of ZmSOS1, ZmHKT1, and ZmMHA2.
• Quantified plasma membrane H+-ATPase activity and Na+ efflux/H+ influx inhibition efficiencies.

Main Results:

• aco2-cr mutants showed significantly lower Na+ accumulation and Na+/K+ ratios compared to wild-type and ACO2-OE plants.
• Mutants exhibited increased expression of ZmSOS1 and ZmHKT1, enhancing root Na+ efflux and reducing root-to-shoot Na+ transport.
• aco2-cr mutants displayed higher ZmMHA2 expression and plasma membrane H+-ATPase activity, promoting root H+ efflux for SOS1 function.
• ACO2-OE plants showed salt sensitivity, while aco2-cr mutants demonstrated improved salt tolerance.

Conclusions:

• Salt-induced ethylene inhibits plasma membrane H+-ATPase and SOS1, disrupting Na+/H+ homeostasis and decreasing Na+ efflux in maize roots.
• Reducing ethylene levels enhances maize salt tolerance by optimizing Na+/H+ balance.
• Manipulating ethylene levels presents a potential strategy for improving maize salt tolerance.