ABSTRACT
Objective To research the effects of drought stress on activity of key enzyme in saikosaponin biosynthesis and saponins content in Bupleurum chinense; To reveal response of Bupleurum chinense to drought stress from protein level. Methods Bupleurum chinense was cultivated in potted water control experiment with 70%–80%, 60%–70%, 40%–50% and 20%–30% saturated soil water contents. The enzyme activities of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR), isoprenyl-based coke (IPPI), farnesyl pyrophosphate synthase (FPS) and β-carotenoid synthase (β-AS) of six months and one year old Bupleurum chinense were measured. The contents of saikosaponins a and d in samples of different soil water contents were determined by HPLC. Results When the saturated moisture was 40%–50%, the enzymatic activities of HMGR, IPPI, FPS and β-AS were the highest, followed by saturated moisture 60%–70%、70%–80% and 20%–30%. The trend of saikosaponin was similar to that of the activity of key enzyme. Conclusion 40%–50% soil saturated water content can significantly increase the activity of the key enzymes in the saikosaponin synthesis pathway. The saponin content and enzyme activity show a significant positive correlation, indicating that under drought stress, Bupleurum chinense regulates the synthesis of saikosaponin by regulating the key enzyme activity of saikosaponin synthesis pathway to respond drought stress.