Abstract
The dried root of Salvia miltiorrhiza is a renowned traditional Chinese medicine that was used for over 1000 years in China. Salvianolic acid B (SalB) is the main natural bioactive product of S. miltiorrhiza. Although many publications described the regulation mechanism of SalB biosynthesis, few reports simultaneously focused on S. miltiorrhiza root development. For this study, an R2R3-MYB transcription factor gene (SmMYB52) was overexpressed and silenced, respectively, in S. miltiorrhiza sterile seedlings. We found that SmMYB52 significantly inhibited root growth and indole-3-acetic acid (IAA) accumulation, whereas it activated phenolic acid biosynthesis and the jasmonate acid (JA) signaling pathway. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed that SmMYB52 suppressed the transcription levels of key enzyme-encoding genes involved in the IAA biosynthetic pathway and activated key enzyme-encoding genes involved in the JA and phenolic acid biosynthesis pathways. In addition, yeast one-hybrid (Y1H) and dual-luciferase assay showed that SmMYB52 directly binds to and activates the promoters of several key enzyme genes for SalB biosynthesis, including SmTAT1, Sm4CL9, SmC4H1, and SmHPPR1, to promote the accumulation of SalB. This is the first report of a regulator that simultaneously affects root growth and the production of phenolic acids in S. miltiorrhiza.
Highlights
The rhizome of Salvia miltiorrhiza, referred to as Danshen in Chinese traditional medicine, contains hydrophilic phenolic acids and lipophilic tanshinones, which are major bioactive constituents that were well-studied over the last few years [1]
SmMYB52, which encodes an R2R3-MYB transcription factors (TFs) that is closely related to Arabidopsis AtMYB93, showed the highest transcript level in the root [26]
We verified that SmMYB52 was a positive regulator for the biosynthesis of rosmarinic acid (RA) and salvianolic acid B (SalB) (Figure 4C,D)
Summary
The rhizome of Salvia miltiorrhiza, referred to as Danshen in Chinese traditional medicine, contains hydrophilic phenolic acids and lipophilic tanshinones, which are major bioactive constituents that were well-studied over the last few years [1]. Phenolic acids in S. miltiorrhiza primarily include two important naturally bioactive products, rosmarinic acid (RA) and salvianolic acid B (SalB), which play important roles in improving microcirculation and inhibiting platelet aggregation [2,3]. Due to their remarkable pharmacological activities and growing market demand, the regulation of SalB biosynthesis in S. miltiorrhiza recently garnered significant attention [4,5]. The R2R3-MYB family functions in a variety of plant-specific regulatory networks that control the development, secondary metabolism, stress mechanisms, and responses to biotic and abiotic stresses [8,9,10,11]. In Arabidopsis thaliana, the R2R3-MYB TF gene AtMYB93 can be induced by auxin, and it negatively regulates lateral root development by interacting with lateral-root-promoting ARABIDILLO proteins [12]
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