Upregulation of isoprenoid pathway genes during enhanced saikosaponin biosynthesis in the hairy roots of Bupleurum falcatum.
In order to characterize saikosaponin biosynthesis in Bupleurum falcatum, the expression of five isoprenoid pathway genes and their relationship to saikosaponin accumulation in the hairy roots were analyzed. The hairy roots exhibited a rapid accumulation of saikosaponins when incubated in a root culture medium (3XRCM). Homology-based RT-PCR was used to isolate core fragments of five genes, HMGR, IPPI, FPS, SS, and OSC, from the hairy roots. The deduced amino acid sequences exhibited amino acid identities of more than 85% to previously reported genes. Using the fragments as probes, the expression of these five genes in the hairy roots during incubation in 3XRCM medium was examined. Expression of all five genes in the hairy roots increased soon after incubation. In particular, the SS and OSC genes were coordinately induced at 8 days of incubation, and their expression persisted throughout the incubation period. A quantitative HPLC analysis showed that the saikosaponin content of the hairy root culture also began to increase at 8 days of culture. The correlation between SS transcript level and saikosaponin content in the hairy roots suggests that transcriptional regulation plays a regulatory role in saikosaponin biosynthesis.
Kim
Young Soon
YS
Department of Life Science, Seonam University, Namwon 590-170, Korea.
Cho
Jung Hyun
JH
Ahn
Juncheul
J
Hwang
Baik
B
D000595:Amino Acid Sequence; D029972:Bupleurum / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009828:Oleanolic Acid / Q000031:analogs & derivatives*; D018517:Plant Roots / Q000378:metabolism*; D012503:Saponins / Q000096:biosynthesis*; D016415:Sequence Alignment; D013729:Terpenes / Q000378:metabolism*; D015854:Up-Regulation
D012503:Saponins; D013729:Terpenes; D009828:Oleanolic Acid; C025759:saikosaponin D