Strengthening Triterpene Saponins Biosynthesis by Over-Expression of Farnesyl Pyrophosphate Synthase Gene and RNA Interference of Cycloartenol Synthase Gene in Panax notoginseng Cells
Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
School of Biotechnology and Engineering, Dianxi Science and Technology Normal University, Lincang 677000, China
Author to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Molecules 2017, 22(4), 581; https://doi.org/10.3390/molecules22040581
Received: 21 February 2017 / Revised: 20 March 2017 / Accepted: 30 March 2017 / Published: 5 April 2017
(This article belongs to the Special Issue Isoprenoid Biosynthesis)
To conform to the multiple regulations of triterpene biosynthesis, the gene encoding farnesyl pyrophosphate synthase (FPS) was transformed into Panax notoginseng (P. notoginseng) cells in which RNA interference (RNAi) of the cycloartenol synthase (CAS) gene had been accomplished. Transgenic cell lines showed both higher expression levels of FPS and lower expression levels of CAS compared to the wild-type (WT) cells. In the triterpene and phytosterol analysis, transgenic cell lines provided a higher accumulation of total triterpene saponins, and a lower amount of phytosterols in comparison with the WT cells. Compared with the cells in which RNAi of the CAS gene was achieved, the cells with simultaneously over-expressed FPS and silenced CAS showed higher triterpene contents. These results demonstrate that over-expression of FPS can break the rate-limiting reaction catalyzed by FPS in the triterpene saponins biosynthetic pathway; and inhibition of CAS expression can decrease the synthesis metabolic flux of the phytosterol branch. Thus, more precursors flow in the direction of triterpene synthesis, and ultimately promote the accumulation of P. notoginseng saponins. Meanwhile, silencing and over-expressing key enzyme genes simultaneously is more effective than just manipulating one gene in the regulation of saponin biosynthesis.