Propiconazole and Tianfengsu Regulated the Growth, Flavor, and Nutrition of Brassica rapa by Brassinosteroid Pathway

Propiconazole (PCZ) and Tianfengsu (TFS) are widely used plant growth regulators in vegetable production for improving crop growth, quality, and flavor. This study investigated the effects of PCZ and TFS, applied individually or in combination, on the growth, development, flavor quality, and nutritional components of choy sum (Brassica rapa) and Arabidopsis thaliana, as well as the underlying molecular mechanisms. The results showed that PCZ inhibited the growth of choy sum and Arabidopsis but enhanced the accumulation of flavor compounds such as soluble sugars, proteins, and vitamin C. In contrast, TFS promoted plant growth and increased the content of nutritional components, including chlorophyll and unsaturated fatty acids. Notably, the combined application of PCZ and TFS significantly improved overall plant quality, achieving the optimal balance of flavor and nutritional value while maintaining high yield. Transcriptomic analysis revealed the molecular mechanisms of PCZ and TFS in differentially regulating the expression of brassinosteroid (BR) signaling and downstream metabolism-related genes. Weighted gene co-expression network analysis (WGCNA) further identified key gene modules and hub genes controlling flavor metabolism in choy sum. This study elucidates the synergistic mechanisms of PCZ and TFS in regulating vegetable growth and quality formation, providing valuable insights for the safe production of high-quality choy sum and the development of novel plant growth regulators or elite varieties. HIGHLIGHTSO_LIPCZ and TFS treatments differentially modulate choy sum growth and development by regulating the BR pathway, with PCZ inhibiting while TFS promoting growth. C_LIO_LIPCZ enhances the accumulation of soluble sugars, soluble proteins, and vitamin C, while TFS increases photosynthetic pigments and unsaturated fatty acids, synergistically improving the flavor and nutritional quality of choy sum. C_LIO_LITranscriptomic analysis and WGCNA uncover key genes and modules controlling flavor metabolism in choy sum, providing potential targets for developing novel plant growth regulators or breeding elite varieties C_LI