Mechanism analysis of uniconazole pretreatment improving waterlogging tolerance of different genotypes of Brassica napus L.

BACKGROUND: Despite the fact that the mechanism by which uniconazole improves waterlogging tolerance in rapeseed remains poorly understood, it has been widely applied to relieve waterlogging injury in crops. RESULTS: Waterlogging-sensitive cultivar ZS6 and tolerant cultivar HYZ50 were treated with uniconazole and waterlogging to explore the mechanism. The results showed that uniconazole improving waterlogging tolerance of rapeseed varied with cultivars. Metabolomic revealed that uniconazole pretreatments affected 79 and 72 metabolic pathways in the roots of ZS6 and HYZ50, corresponding to 579 and 458 DEMs, respectively. Transcriptomic identified 1761 and 1527 DEGs in the roots of ZS6 and HYZ50, involving 108 and 103 metabolic pathways, respectively, and 8 core KEGG metabolic pathways were co-enriched in the two cultivars. Uniconazole pretreatment activated the stress response pathway in ZS6, but reinforced cell wall integrity and oxidative defense in HYZ50. Uniconazole pretreatment triggered the stress response pathway, facilitating the specific enrichment of DEGs and DEMs in linoleic acid metabolism, α-linolenic acid metabolism, and phenylalanine metabolism pathways in ZS6. Owing to its weak basal waterlogging tolerance, ZS6 exhibited insufficient antioxidant defense, membrane repair, and osmotic regulation, making it more prone to injury under waterlogging stress. Root activity exhibited an upward trend in ZS6, but lower than that in HYZ50. Soluble sugar content first decreased and then increased. Photosynthetic pigments displayed an upward trend, but the overall level is low compared with than in ZS6. In contrast, HYZ50 displayed robust waterlogging tolerance. CONCLUSION: Uniconazole pretreatment modulated the phenylpropanoid biosynthesis pathway to reinforce cell wall integrity and augment oxidative defense, while coordinating tryptophan metabolism to sustain root function and signal transduction. This study established novel metabolic regulatory pathways for cultivar-specific waterlogging tolerance in Brassica napus.