Enhanced production of phenolic acids in Salvia miltiorrhiza hairy root cultures by combing the RNAi-mediated silencing of chalcone synthase gene with salicylic acid treatment

Salvia miltiorrhiza is an important traditional Chinese herb in China and some other Asian countries. Phenolic acids are bioactive compounds in S. miltiorrhiza, the biosynthesis of which shares the general phenylpropanoid pathway with flavonoids. Chalcone synthase (CHS) is the entry point enzyme of the flavonoid pathway and plays a crucial role in flavonoid biosynthesis. In this study, the transcript of CHS was suppressed through RNAi-mediated silencing, and salicylic acid (SA) was added to the CHS silencing lines and wild-type lines as elicitor to investigate effects of the genetic modification and/or elicitor treatment on the production of phenolic acids in S. miltiorrhiza hairy roots. The results showed that the silencing of CHS enhanced contents of phenolic acids and decreased the accumulation of total flavonoids. The contents of phenolic acids in the SA treated CHS silencing lines were much higher than that in the CHS silencing lines and the SA treated wild-type lines. Our results imply that the substrate flow is directed to the phenolic acids pathway when the flavonoid pathway is interrupted, and combining the genetic modification and elicitor treatment is a new way to improve the production of phenolic acids in S. miltiorrhiza hairy root cultures.