Salvia miltiorrhiza (Danshen in Chinese), is a well-known traditional Chinese medicinal plant, which is used as not only human medicine but also health-promotion food. Danshen has been extensively used for the treatment of various cardiovascular and cerebrovascular diseases. As a major group of bioactive constituents from S. miltiorrhiza, water-soluble phenolic acids such as salvianolic acid B possessed good bioactivities including antioxidant, anti-inflammatory, anti-cancer and other health-promoting activities. It is of significance to improve the production of phenolic acids by modern biotechnology approaches to meet the increasing market demand. Significant progresses have been made in understanding the biosynthetic pathway and regulation mechanism of phenolic acids in S.miltiorrhiza, which will facilitate the process of targeted metabolic engineering or synthetic biology. Furthermore, multiple biotechnology methods such as in vitro culture, elicitation, hairy roots, endophytic fungi and bioreactors have been also used to obtain pharmaceutically active phenolic acids from S. miltiorrhiza. In this review, recent advances in bioactivities, biosynthetic pathway and biotechnological production of phenolic acid ingredients were summarized and future prospective was also discussed.

No abstract

Water-soluble phenolic acids are major bioactive compounds in the medicinal plant species Salvia miltiorrhiza. Phenolic acid biosynthesis is induced by methyl jasmonate (MeJA) in this important Chinese herb. Here, we investigated the mechanism underlying this induction by analyzing a transcriptome library of S. miltiorrhiza in response to MeJA. Global transcriptome analysis identified the MeJA-responsive R2R3-MYB transcription factor-encoding gene SmMYB1. Overexpressing SmMYB1 significantly promoted phenolic acid accumulation and upregulated the expression of genes encoding key enzymes in the phenolic acid biosynthesis pathway, including cytochrome P450-dependent monooxygenase (CYP98A14). Dual-luciferase (dual-LUC) assays and/or an electrophoretic mobility shift assays (EMSAs) indicated that SmMYB1 activated the expression of CYP98A14, as well as the expression of genes encoding anthocyanin biosynthesis pathway enzymes, including chalcone isomerase (CHI) and anthocyanidin synthase (ANS). In addition, SmMYB1 was shown to interact with SmMYC2 to additively promote CYP98A14 expression compared to the action of SmMYB1 alone. Taken together, these results demonstrate that SmMYB1 is an activator that improves the accumulation of phenolic acids and anthocyanins in S. miltiorrhiza. These findings lay the foundation for in-depth studies of the molecular mechanism underlying MeJA-mediated phenolic acid biosynthesis and for the metabolic engineering of bioactive ingredients in S. miltiorrhiza.

MYB transcription factors play vital roles in plant growth and metabolism. The phytohormone methyl jasmonate (MeJA) promotes phenolic acid accumulation in the medicinal herb Salvia miltiorrhiza, but the regulatory mechanism is poorly understood. Here, we identified the MeJA-responsive R2R3-MYB transcription factor gene SmMYB2 from a transcriptome library produced from MeJAtreated S. miltiorrhiza hairy roots. SmMYB2 expression was tightly correlated with the expression of key salvianolic acid biosynthetic genes including CYP98A14. SmMYB2 was highly expressed in the periderm of S. miltiorrhiza and SmMYB2 localized to the nucleus. Overexpressing SmMYB2 in S. miltiorrhiza hairy roots significantly increased the levels of salvianolic acids (including rosmarinic acid and salvianolic acid B) by upregulating salvianolic acid biosynthetic genes such as CYP98A14. SmMYB2 binds to the MYB-binding motifs in the promoter of CYP98A14, as confirmed by a dual-luciferase assay and electrophoretic mobility shift assays. Anthocyanin contents were significantly higher in SmMYB2-overexpressing hairy root lines than the control, primarily due to the increased expression of CHI, DFR, and ANS. These findings reveal the novel regulatory role of SmMYB2 in MeJA-mediated phenolic acid biosynthesis, providing a useful target gene for metabolic engineering and shedding light on the salvianolic acid regulatory network.