Han Jung Yeon, Kwon Yong Soo, Yang Deok Chun, Jung Young Rim, Choi Yong Eui
College of Pharmacy, Kangwon National University, Chunchon 200-701, Republic of Korea.
Plant Cell Physiol. 2006 Dec;47(12):1653-62. doi: 10.1093/pcp/pcl032. Epub 2006 Nov 6.
Panax ginseng is one of the most highly valued herbal medicines in the Orient, where it has gained an almost magical reputation for being able to maintain the quality of life. The root of ginseng contains noble tetracyclic triterpenenoid saponins, which are thought to be the major effective ingredients in P. ginseng. The first committed step in ginsenoside synthesis is the cyclization of 2,3-oxidosqualene to dammarenediol II by oxidosqualene cyclase, dammarenediol synthase (DDS). The gene encoding DDS has been characterized. Here, we investigated the expression of the DDS gene together with the genes involved in ginsenoside biosynthesis (SS, SE, PNX, PNY, PNY2 and PNZ). Expression of DDS mRNA was higher in flower buds compared with root, leaf and petiole of ginseng plants. Elicitor (methyl jasmonate) treatment up-regulated the expression of DDS mRNA. Ectopic expression of DDS in a yeast mutant (erg7) lacking lanosterol synthase resulted in the production of dammarenediol and hydroxydammarenone which were confirmed by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC/APCIMS). RNA interference (RNAi) of DDS in transgenic P. ginseng resulted in silencing of DDS expression which leads to a reduction of ginsenoside production to 84.5% in roots. These results indicate that expression of DDS played a vital role in the biosynthesis of ginsenosides in P. ginseng.
人参是东方最受珍视的草药之一，在那里它因能够维持生活质量而赢得了近乎神奇的声誉。人参根中含有珍贵的四环三萜皂苷，被认为是人参的主要有效成分。人参皂苷合成的第一个关键步骤是氧化鲨烯环化酶（达玛烯二醇合酶，DDS）将2,3-氧化鲨烯环化为达玛烯二醇II。编码DDS的基因已得到表征。在此，我们研究了DDS基因以及参与人参皂苷生物合成的基因（SS、SE、PNX、PNY、PNY2和PNZ）的表达情况。与人参植株的根、叶和叶柄相比，花芽中DDS mRNA的表达更高。诱导剂（茉莉酸甲酯）处理上调了DDS mRNA的表达。在缺乏羊毛甾醇合酶的酵母突变体（erg7）中异位表达DDS，导致产生了达玛烯二醇和羟基达玛烯酮，这通过液相色谱-大气压化学电离质谱法（LC/APCIMS）得到了证实。在转基因人参中对DDS进行RNA干扰（RNAi）导致DDS表达沉默，从而使根中人参皂苷的产量降低至84.5%。这些结果表明，DDS的表达在人参中人参皂苷的生物合成中起着至关重要的作用。
