Transcriptomic Insights Into Brassinolide-Mediated Control of Bioactive Compound Biosynthesis in Salvia miltiorrhiza...

Brassinolide (BR) plays a pivotal role in regulating plant secondary metabolism and can promote the accumulation of bioactive compounds. However, relatively few studies have explored the application of BR in Salvia miltiorrhiza, and the mechanistic basis for its function in this context remains poorly understood.

In this study, S. miltiorrhiza hairy roots were treated with BR at 1 μM and 5 μM. The treated samples were analyzed via high-performance liquid chromatography (HPLC)-based chemical quantification, transcriptomic sequencing, and quantitative real-time polymerase chain reaction (qRT-PCR) validation to systematically elucidate the concentration-dependent and time-dependent molecular mechanisms underlying BR-mediated biosynthesis of tanshinones and salvianolic acids in S. miltiorrhiza.

BR treatment at the 1 μM dose level significantly induced the accumulation of rosmarinic acid, salvianolic acid B, and tanshinone IIA, with respective 1.43, 1.82, and 1.78-fold increases in the levels of these compounds compared to controls. Expression of most key biosynthetic genes involved in the salvianolic acid and tanshinone biosynthesis pathways peaked at 1 h after treatment with 1 μM BR. Further transcriptomic analysis identified 15 significantly upregulated transcription factors that may regulate tanshinone and salvianolic acid biosynthesis. These differentially expressed genes were primarily enriched in the phenylpropanoid and terpenoid pathways. qRT-PCR validation confirmed the consistency and reliability of these transcriptomic data.

Collectively, these findings reveal that BR treatment enhances secondary metabolism in S. miltiorrhiza by orchestrating changes in the expression of key structural genes and transcription factors, providing a theoretical basis for the breeding of high-quality germplasm resources.