Enhanced triterpene and phytosterol biosynthesis in Panax ginseng overexpressing squalene synthase gene.
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), beta-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.
Lee
Mi-Hyun
MH
Korea Ginseng Institute, Chung-Ang University, Ansung 456-756, Kyunggi-do, Korea.
Jeong
Jae-Hun
JH
Seo
Jin-Wook
JW
Shin
Cha-Gyun
CG
Kim
Young-Soon
YS
In
Jun-Gygo
JG
Yang
Deok-Chun
DC
Yi
Jae-Seon
JS
Choi
Yong-Eui
YE
D000085:Acetates / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000096:biosynthesis / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics*; D036145:Ginsenosides / Q000096:biosynthesis*; D019751:Intramolecular Transferases / Q000235:genetics*; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000235:genetics*; D054883:Oxylipins; D005894:Panax / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010840:Phytosterols / Q000096:biosynthesis*; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D018520:Plant Shoots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D050603:Squalene Monooxygenase; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*
D000085:Acetates; D003517:Cyclopentanes; D036145:Ginsenosides; D054883:Oxylipins; D010840:Phytosterols; D012333:RNA, Messenger; C072239:methyl jasmonate; D010105:Oxygenases; D050603:Squalene Monooxygenase; D013186:Farnesyl-Diphosphate Farnesyltransferase; D019751:Intramolecular Transferases; C039924:2,3-oxidosqualene-beta-amyrin-cyclase