Enhanced triterpene and phytosterol biosynthesis in Panax ginseng overexpressing squalene synthase gene
Enhanced triterpene and phytosterol biosynthesis in Panax ginseng overexpressing squalene synthase gene
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DOI：
10.1093/pcp/pch126
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发表时间：
2004-08-01
影响因子：
4.9
通讯作者：
Choi, YE
中科院分区：
文献类型：
--
作者：
Lee, MH;Jeong, JH;Choi, YE
人参是世界著名的药用植物之一，其根中含有多种植物甾醇和具有生物活性的三萜皂苷。在P人参中，植物甾醇和三萜共享共同的生物合成中间体角鲨烯。在这里，我们调查人参角鲨烯合酶（PgSS 1）的植物甾醇和三萜皂苷的生物合成的调节作用。PgSS 1转录本在各种植物组织中普遍表达，但在茎尖和根中表达较高。茉莉酸甲酯（MeJA）处理后12 ~ 96 h，不定根中PgSS 1的转录水平显著升高，诱导角鲨烯环氧酶（SE）、β-香树脂素合成酶（bAS）的转录激活，但不诱导环阿屯醇合成酶（CAS）的转录激活。与MeJA处理不同，PgSS 1在转基因人参不定根中的过表达随后是所有下游基因的上调，如SE、bAS和CAS。PgSS 1酶活性的增强导致植物甾醇和甾醇含量的显著增加。这些结果表明，PgSS 1不仅是植物甾醇的关键调控酶，也是三萜生物合成的关键调控酶，并且PgSS 1的过表达赋予人参三萜皂苷的超生产。
Roots of Panax ginseng, one of the most famous medicinal plants, contain various phytosterols and bioactive triterpene saponins (ginsenosides). In P ginseng, phytosterols and triterpenes share the common biosynthetic intermediate, squalene. Here, we investigate the regulatory role of Panax ginseng squalene synthase (PgSS1) on the biosynthesis of phytosterols and triterpene saponins. PgSS1 transcripts are expressed ubiquitously in the various plant tissues, but higher in shoot apex and root. The transcript levels of PgSS1 increased markedly in the adventitious roots during 12- to 96-h period after metyl jasmonate (MeJA) treatment; MeJA treatment induced the activation of the transcripts of squalene epoxidase (SE), P-amyrin synthase (bAS), but not cycloartenol synthase (CAS). Unlike MeJA treatment, overexpression of PgSS1 in adventitious roots of transgenic P ginseng was followed by the up-regulation of all the downstream genes tested, such as SE, bAS, and CAS. The enhanced activity of PgSS1 enzyme resulted in remarkable increase of phytosterols as well as ginsenoside contents. These results demonstrate that PgSS1 is a key regulatory enzyme not only for phytosterol but also for triterpene biosynthesis and overexpressing of PgSS1 confers the hyperproduction of triterpene saponins to P ginseng.