The Oplopanax elatus genome reveals dammaradienol synthase evolution enabling reconstruction of RK type ginsenosides biosynthesis

Abstract

Abstract RK-type ginsenosides are a subgroup of dehydrated dammarane saponins with valuable bioactivities, but they are not naturally produced in cultivated ginseng. The ginseng relative Oplopanax elatus accumulates dammaradienol, the precursor scaffold of RK-type ginsenosides, but does not produce RK-type ginsenosides. Here, we identify OeOSC14 as a specialized dammaradienol synthase that evolved through duplication and neofunctionalization of an ancestral multifunctional triterpene synthase by combining chromosome-level genome assembly, comparative genomics and biochemical analyses. Consistent with this evolutionary transition, a single N260Y substitution converts OeOSC14 from a dammaradienol-specific enzyme back into a multifunctional triterpene synthase. We further show that loss of functional C12 hydroxylase blocks the downstream oxidative step required for RK-type ginsenoside biosynthesis in O. elatus . Reconstitution of the pathway in Nicotiana benthamiana enables de novo production of ginsenosides Rk1, Rk2, and Rk3, providing evolutionary insight into triterpene diversification and establishing a plant-based route for producing these compounds.