Ethylene-mediated integration of metabolic regulation and stomatal closure for enhanced waterlogging tolerance in Brassica napus L.

Waterlogging causes hypoxic stress that severely limits Brassica napus L.growth and yield, yet leaf-specific ethylene regulation in tolerant versus sensitive genotypes is poorly understood. We compared a tolerant line (126) and a sensitive line (85) to clarify ethylene’s role in aerial adaptation. After 10 days of flooding, 85 exhibited greater growth inhibition, chlorophyll loss, and lipid peroxidation, whereas 126 maintained higher survival, photosynthetic integrity, and metabolic stability. In 126, waterlogging strongly enhanced ethylene biosynthesis via increased S-adenosylmethionine synthetase, ACC synthase, and ACC oxidase activities, alongside BnEIN3 and BnERF73 upregulation, resulting in a 94.08 % ethylene increase. Ethylene inhibition by silver thiosulfate reduced antioxidant enzyme activities (SOD, CAT, POD), aggravated oxidative injury, altered stomatal closure, and shifted cell wall composition. Genotype-specific patterns emerged: 126 directed ethylene-mediated remodeling toward lignin deposition with moderate ABA involvement, optimizing structural defense and gas exchange; 85 relied on ethylene–ABA-driven stomatal closure and cellulose/hemicellulose reinforcement but showed lower antioxidant efficiency. Ethylene degradation changed little, indicating synthesis as the primary determinant of leaf ethylene levels. These results demonstrate that rapid ethylene amplification in tolerant genotypes coordinates antioxidant defense, stomatal regulation, and cell wall remodeling to confer flooding resilience, offering mechanistic insight and breeding targets for waterlogging tolerance in B. napus. • Compared leaf-specific ethylene regulation between waterlogging-tolerant and sensitive Brassica napus L. genotypes. • Tolerant genotype (126) rapidly enhanced SAMS–ACS–ACO activities, elevating ethylene by 94.1 % under flooding. • Ethylene inhibition reduced antioxidant enzyme activity and aggravated oxidative damage, especially in tolerant plants. • 126 directed ethylene-mediated lignin deposition, while 85 relied on cellulose/hemicellulose reinforcement.