A CYP76AH1 RNAi system for Danshen hairy roots is constructed.
The in vivo catalytic activity of CYP76AH1 is revealed by RNAi system.
The RNAi system verified the key role of CYP76AH1 in the biosynthesis of tanshinones.
CYP76AH1 could be used as a target for metabolic engineering.