Investigating the integrated mechanism of exogenous 24-epibrassinolide regulating antioxidant and detoxification metabolic networks to mitigate propiconazole-induced stress in Panax notoginseng

Plant stress caused by excessive chemical pesticide use is a key bottleneck restricting the safe production and quality improvement of medicinal herbs. This study focuses on the regulatory role and mechanism of the plant hormone brassinosteroids (BRs) in alleviating pesticide stress in medicinal plants. Using three-year-old Panax notoginseng as the model organism, a pesticide stress model was created by foliar spraying with 0.6 g L⁻¹ propiconazole (PPC), and the alleviating effect of 0.1 μM 24-epibrassinolide (EBR) pretreatment on the stress was examined. The results showed that EBR pretreatment significantly reversed the growth inhibition of P. notoginseng caused by PPC stress. Physiological and biochemical analyses revealed that EBR comprehensively enhanced the antioxidant defense capacity of P. notoginseng to counteract oxidative damage. Simultaneously, it restored the glutathione (GSH) metabolic balance, increasing reduced GSH content by 26.5%, and elevating the activities of glutathione-S-transferase (GST) and glutathione reductase (GR) by 23.4% and 41.8%, respectively, thereby effectively scavenging excess reactive oxygen species (ROS). Importantly, RNA-Seq transcriptomic analysis revealed that EBR pretreatment induced 641 differentially expressed genes (DEGs). These DEGs showed significant enrichment in pathways including glutathione metabolism, MAPK signaling pathway-plant, phenylpropanoid biosynthesis, and plant hormone signal transduction. In summary, this study elucidates that EBR acts not through a single pathway but by synergistically activating an integrated defense and detoxification system centered on the GSH metabolism-based antioxidant system and the xenobiotic binding and transport-centric detoxification network. This research offers new perspectives for elucidating the complex regulatory networks of plants in response to pesticide-induced organic pollutant stress.