镧对人参发根中皂苷积累及合成关键酶基因表达的影响

Effects of Lanthanum on Accumulation of Ginsenosides and Expression of Key Enzymes Genes of Ginsenosides Biosynthesis in Hairy Roots of Panax Ginseng

以不同浓度镧处理人参发根, qRT-PCR检测人参皂苷合成关键酶基因PgSS,PgDDS和PgβAS的表达水平, HPLC测定人参皂苷含量,探讨镧对人参发根生长及其人参皂苷合成影响的作用机制。镧浓度分别为5.0, 10.0和15.0 mg·L^-1时,促进发根伸长、根毛形成和重量增加, 20.0, 25.0和30.0 mg·L^-1时,抑制发根生长;PgSS和PgDDS基因表达水平对镧呈浓度依赖性变化, 20.0 mg·L^-1时,PgSS和PgDDS基因表达量均显著增加(P<0.05)且达到最大,高于20.0 mg·L^-1时,PgSS和PgDDS基因表达水平随镧浓度升高而降低;镧对PgβAS基因表达无明显影响。镧促进发根中人参皂苷Rb1, Rb2, Rc, Rd, Re, Rg1和总皂苷含量增加,人参皂苷合成积累规律与PgSS和PgDDS基因表达规律一致,当镧浓度为20.0 mg·L^-1时,人参皂苷产量亦达到最高。表明镧可以调节人参发根的生长,通过促进人参皂苷合成关键酶基因PgSS和PgDDS的表达增加人参皂苷的生物合成与积累。

To investigate the effect of lanthanum(La) on the ginsenosides biosynthesis and its key enzymes genes expression in hairy roots of Panax ginseng. La was added to the media of ginseng hairy roots with 0.0, 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 mg·L^-1, respectively. The expression levels of PgSS, PgDDS and PgβAS genes were identified by qRT-PCR, and the content of ginsenoside Rb1, Rb2, Rc, Rd, Re, Rg1 and total saponins was assayed by HPLC. The correlation between expression profiles of key enzymes genes and the ginsenosides biosynthesis and accumulation was also analyzed. The results indicated that La enhances the extension, root hair formation and biomass of ginseng hairy roots at 5.0, 10.0 and 15.0 mg·L^-1, and the growth of hairy roots is inhibited by La at 20.0, 25.0 and 30 mg·L^-1. PgSS and PgDDS genes expression is induced by La in a concentration dependent way, and the expression level increases obviously(P<0.05) and reaches the highest level at 20.0 mg·L^-1, and then decreases. However, La does not affect the PgβAS gene. At the meantime, biosynthesis and accumulation of ginsenoside Rb1, Rb2, Rc, Rd, Re, Rg1, total saponins increase obviously in a same way of the expression patterns of PgSS and PgDDS genes, the yeild of ginsenosides reaches to the climax at 20.0 mg·L^-1 La. In conclusion, La can improve the expression of PgSS and PgDDS genes and its corresponding metabolites ginsenoside in hairy roots of P. ginseng. This work provides a foundation for investigation of the accumulation mechanism of ginsenosides under the control of La in P. ginseng.