Effect of Over-expressing Farnesyl Pyrophosphate Synthase (FPS) Gene of Panax notoginseng Cell on Saponin Synthesis
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Abstract:
To study the effect of over-expressing farnesyl pyrophosphate synthase (FPS) in Panax notoginseng (P. notoginseng) cells on saponin synthesis, an FPS over-expression vector was constructed and integrated into the genome of P. notoginseng cells via Agrobacterium tumefaciens. Relative expression levels of FPS in the positive cell lines were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). The contents of Panax notoginseng saponins (PNSs) and monomer ginsenosides were estimated by vanillin-perchloric acid-glacial acetic acid colorimetric method and high performance liquid chromatography (HPLC), respectively. The results showed that the relative FPS expression levels and PNS content were both higher in the four transgenic FPS-positive cell lines, than those in non-transgenic control, with highest levels at 3.01-times and 2.09-times higher, respectively. Additionally, the content of important monomer ginsenosides (Rh1, Rg1, Re, and Rd) were all higher in the four transgenic FPS-positive cell lines than those in the non-transgenic control. Among these, the increase in Re content was the most significant, with highest level was up to 4.35 times as much as that of control. Moreover, the content of Rh1, Rd, and Rg1 were increased to some extent as well, with highest levels at 2.66-, 2.90-, 1.76-times that of the control, respectively. These results suggest that FPS is one of the rate-limiting enzymes in the PNS biosynthetic pathway. Thus, over-expressing FPS in P. notoginseng cells could enhance PNS content, which has potential applications in metabolic engineering to realize homologous or heterologous expression of PNS.
