The SmMYB36-SmERF6/SmERF115 module regulates the biosynthesis of tanshinones and phenolic acids in salvia miltiorrhiza hairy roots.

Tanshinone and phenolic acids are the most important active substances of , and the insight into their transcriptional regulatory mechanisms is an essential process to increase their content . SmMYB36 has been found to have important regulatory functions in the synthesis of tanshinone and phenolic acid; paradoxically, its mechanism of action in is not clear. Here, we demonstrated that SmMYB36 functions as a promoter of tanshinones accumulation and a suppressor of phenolic acids through the generation of overexpressed and chimeric -SRDX (EAR repressive domain) repressor hairy roots in combination with transcriptomic-metabolomic analysis. SmMYB36 directly down-regulate the key enzyme gene of primary metabolism, , up-regulate the tanshinones biosynthesis branch genes , , and down-regulate the phenolic acids biosynthesis branch enzyme gene, . Meanwhile, SmERF6, a positive regulator of tanshinone synthesis activating , was up-regulated and SmERF115, a positive regulator of phenolic acid biosynthesis activating , was down-regulated. Furthermore, the seven acidic amino acids at the C-terminus of SmMYB36 are required for both self-activating domain and activation of target gene expression. As a consequence, this study contributes to reveal the potential relevance of transcription factors synergistically regulating the biosynthesis of tanshinone and phenolic acid.