24-Epibrassinolide Alleviates Tebuconazole Toxicity in Apple through Coordinated Intracellular Detoxification and Extracellular Barrier Fortification.

The extensive use of tebuconazole (TBZ) in apple production raises environmental and health concerns. Here, apple fruits were treated with TBZ alone or pretreated with 24-epibrassinolide (EBR) before TBZ application. Among the tested concentrations, 2 mg/L of EBR reduced TBZ residues by 41.61% at 9 days after treatment. Multiomics analyses showed that EBR induced a transient H2O2 burst, enhanced GST- and UGT-mediated detoxification, promoted cell wall polysaccharide deposition, and increased membrane-associated very-long-chain fatty acid accumulation. Concurrently, EBR reduced the level of accumulation of sugars, amino acids, glycolysis-related metabolites, and fatty acid-derived aroma volatiles. Functional assays further showed that MdGSTU19 overexpression reduced TBZ residues by 41.43% in tobacco, while MdKCS1 or MdKCS6 expression improved the yeast membrane integrity under TBZ stress. These findings indicate that EBR alleviates TBZ toxicity by coordinating intracellular detoxification and extracellular barrier reinforcement while revealing a trade-off between enhanced tolerance and fruit quality.