The Smi-miR858a-SmMYB module regulates tanshinone and phenolic acid biosynthesis in Salvia miltiorrhiza

Abstract

Tanshinones and phenolic acids are two major classes of bioactive compounds in S. miltiorrhiza. Revealing the regulatory mechanism of their biosynthesis is crucial for quality improvement of S. miltiorrhiza medicinal materials. Here we demonstrated that Smi-miR858a–Smi-miR858c, a miRNA family previously known to regulate flavonoid biosynthesis, also played critical regulatory roles in tanshinone and phenolic acid biosynthesis in S. miltiorrhiza. Overexpression of Smi-miR858a in S. miltiorrhiza plants caused significant growth retardation and tanshinone and phenolic acid reduction. Computational prediction, degradome and RNA-seq analyses revealed that Smi-miR858a could directly cleave the transcripts of SmMYB6, SmMYB97, SmMYB111, and SmMYB112. Yeast one-hybrid and transient transcriptional activity assays showed that Smi-miR858a-regulated SmMYBs, such as SmMYB6 and SmMYB112, could activate the expression of SmPAL1 and SmTAT1 involved in phenolic acid biosynthesis and SmCPS1 and SmKSL1 associated with tanshinone biosynthesis. In addition to directly activate the genes involved in bioactive compound biosynthesis pathways, SmMYB6 and SmMYB97 could also activate SmAOC2, SmAOS4 and SmJMT2 involved in the biosynthesis of MeJA, a significant elicitor of plant secondary metabolism. The results suggest the existence of dual signaling pathways for the regulation of Smi-miR858a in bioactive compound biosynthesis in S. miltiorrhiza.

Genome-Wide Identification and Functional Analysis of Salvia miltiorrhiza MicroRNAs Reveal the Negative Regulatory Role of Smi-miR159a in Phenolic Acid Biosynthesis

“…Transgenic S. miltiorrhiza lacking smi-miR408 showed increased levels of rosmarinic acid (RA) and salvianolic acid B (SalB) [35]. Overexpression of smi-miR858a caused a significant reduction in tanshinones and phenolic acids, two major classes of bioactive compounds in S. miltiorrhiza [36].…”

Genome-Wide Identification and Characterization of miRNAs and Natural Antisense Transcripts Show the Complexity of Gene Regulatory Networks for Secondary Metabolism in Aristolochia contorta

“…For instance, ptr-miR397a acts as a negative regulator of laccase genes, affecting lignin biosynthesis in Populus trichocarpa [ 11 ]. Smi-miR858a regulates tanshinone and phenolic acid biosynthesis through cleaving the transcripts of SmMYB6 , SmMYB97 , SmMYB111 , and SmMYB112 in Salvia miltiorrhiza that had its whole genome sequence available [ 12 , 13 ]. Smi-miR159a mediates SmMYB62 , SmMYB78 , and SmMYB80 to regulate phenolic acid biosynthesis in S. miltiorrhiza [ 14 ].…”