Mitochondrial AOX1a and an H₂O₂ feed-forward signalling loop regulate flooding tolerance in rice

Area of Science:

• Plant Biology
• Molecular Biology
• Agricultural Science

Background:

• Flooding causes significant global yield losses in food production.
• Rice cultivation faces challenges due to waterlogged soils and hypoxia.
• The role of Alternative Oxidase (AOX) in hypoxia tolerance was previously unclear.

Purpose of the Study:

• To investigate the function of AOX1a in rice under hypoxic and flooding conditions.
• To elucidate the molecular mechanisms underlying hypoxia tolerance in rice.
• To identify targets for improving flooding tolerance in crops.

Main Methods:

• Investigated the necessity and sufficiency of AOX1a for rice germination and root development under hypoxia.
• Analyzed the role of hydrogen peroxide (H2O2) in regulating AOX1a expression and function.
• Examined the downstream effects of AOX1a and H2O2 on glycolysis, aerenchyma development, and lateral root emergence.
• Assessed the impact of ectopic AOX1a expression on plant growth and grain yield.

Main Results:

• AOX1a is essential for promoting germination, coleoptile elongation, and root development in rice under hypoxia.
• Hypoxia induces H2O2 accumulation, which activates AOX1a expression.
• AOX1a and H2O2 act interdependently to regulate ATP production, root aerenchyma development, and lateral root emergence.
• Ectopic AOX1a expression enhances root and plant growth, leading to increased grain yield.

Conclusions:

• AOX1a functions as a sensor for low oxygen tension, with H2O2 acting as a second messenger to trigger downstream root development.
• The AOX1a-H2O2 pathway is critical for rice adaptation to flooded environments.
• AOX1a manipulation and H2O2 pretreatment are promising strategies for enhancing flooding tolerance in rice and other crops.