Expansion within the CYP71D subfamily drives the heterocyclization of tanshinones synthesis in Salvia miltiorrhiza

Tanshinones are the bioactive nor-diterpenoid constituents of the Chinese medicinal herb Danshen (Salvia miltiorrhiza). These groups of chemicals have the characteristic furan D-ring, which differentiates them from the phenolic abietane-type diterpenoids frequently found in the Lamiaceae family. However, how the 14,16-epoxy is formed has not been elucidated. Here, we report an improved genome assembly of Danshen using a highly homozygous genotype. We identify a cytochrome P450 (CYP71D) tandem gene array through gene expansion analysis. We show that CYP71D373 and CYP71D375 catalyze hydroxylation at carbon-16 (C16) and 14,16-ether (hetero)cyclization to form the D-ring, whereas CYP71D411 catalyzes upstream hydroxylation at C20. In addition, we discover a large biosynthetic gene cluster associated with tanshinone production. Collinearity analysis indicates a more specific origin of tanshinones in Salvia genus. It illustrates the evolutionary origin of abietane-type diterpenoids and those with a furan D-ring in Lamiaceae. Salvia miltiorrhiza is a medicinal plant that can produce the bioactive tanshinones. Here, the authors report the improved genome assembly and reveal the possible roles of three CYP71Ds in catalyzing the reactions leading to the formation of the characteristic furan D-ring of transhinones.

Automated summary

The study reports the improved genome assembly of Danshen and reveals the possible roles of three CYP71Ds in catalyzing the reactions leading to the formation of the characteristic furan D-ring of tanshinones. The findings shed light on the biosynthetic pathway of tanshinones and highlight the evolutionary origin of different types of diterpenoids in the Lamiaceae family.