Expression patterns of some genes involved in tanshinone biosynthesis in Salvia miltiorrhiza roots

Abstract

Tanshinones are the major bioactive components of Salvia miltiorrhiza, and synthesized through the cytosol-localized mevalonic acid (MVA) and plastid-localized methylerythritol 4-phosphate (MEP) pathways. To reveal correlations between gene expression and tanshinone accumulation, transcript-level variations in five candidate genes involved in tanshinone biosynthesis in the roots of S. miltiorrhiza were investigated at different developmental stages. Additionally, the accumulation of tanshinone I, tanshinone IIA, and cryptotanshinone were analyzed by liquid chromatography tandem mass spectrometry. Compared with the other genes examined, SmCMK (encoding the enzyme 4-diphosphocytidyl-2-C-methyl-D-erythritol kinase) expression was significantly positively correlated with tanshinone production, and SmDXR (1-deoxy-D-xylulose 5-phosphate reductoisomerase) likely functions as a non-rate-limiting enzyme in the tanshinone-biosynthesis pathways of S. miltiorrhiza during different developmental stages, with significant correlations observed between SmDXR and SmCMK expression. Furthermore, no significant correlations were observed between the expression of SmAACT (encoding the enzyme acetyl-CoA acyltransferase), SmHMGR2 (encoding the enzyme 3-hydroxy-3-methylglutaryl-COA reductase), and SmFPPS (encoding the enzyme farnesyl diphosphate synthase), which are involved in the MVA pathway, and tanshinone production during the developmental stages examined, suggesting that the MVA pathway might contribute less to tanshinone accumulation as compared with the MEP pathway. The results in this study indicated that SmCMK might play an important role in their biosynthesis and accumulation. Overall, this study contributes to a better understanding of tanshinone biosynthesis during the different developmental stages of S. miltiorrhiza.