ⓒ The Korean Society of Ginseng 98 http://ginsengres.org pISSN: 1226-8453 eISSN: 2093-4947 Research Article J. Ginseng Res. Vol. 34, No. 2, 98-103 (2010) DOI:10.5142/jgr.2010.34.2.098 E-mail: dcyang@khu.ac.kr Tel: +82-31-201-2688, Fax: +82-31-201-2687 * Corresponding author INTRODUCTION Panax ginseng (P. ginseng) is one of the most well- known oriental medicinal plants. Triterpene saponins (ginsenosides) extracted from the roots of P. ginseng have various kinds of biological activities [1]. Although more than 80 different skeletal types of triterpenes are known to occur naturally, the dammarane-type triterpenes are found only in a few species as major compounds, e.g., P. ginseng [2] and Gynostemma pen- taphyllum (jiaogulan) [3]. Recent research including large-scale gene analysis [4-5] and proteome analysis [6-7] has shown that P. ginseng is one of the most suit- able systems for studying the biosynthesis of damma- rane-type triterpene saponins. The isoprenoid biosynthetic pathway plays an important role in plant metabolism. The best-known metabolites in this pathway are sterols, gibberellins, carotenoids [8], and terpenes such as mono-, sesqui-, di-, and triterpenes [9]. Overproduction of phytosterols and triterpenes by metabolic engineering may be an attractive strategy for producing pharmacologically active medicinal plants of superior quality. Squalene synthase (SQS) (EC 2.5.1.21) catalyzes the frst enzymatic step in the central isopren- oid pathway toward sterol and triterpenoid biosynthesis [10]. As SQS acts at a putative key branching point in the isoprenoid biosynthetic pathway, it may have a reg- ulatory role in this pathway. SQS has been investigated in animals [11], yeast [12], and plants [13-16]. Elicitor-induced accumulation of secondary metabolites has received much attention, and jasmonic acid has proven to be an effective elicitor [17-19]. Jasmonic acid is believed to be an integral component of signal trans- duction pathways resulting in the activation of defense responses and secondary metabolism [20,21]. It was reported that exogenously applied elicitors, particularly Overexpression of PgSQS1 Increases Ginsenoside Production and Negatively Afects Ginseng Growth Rate in Panax ginseng Ju-Sun Shim, Ok Ran Lee, Yu-Jin Kim, Jung-Hye Lee, Ju-Han Kim, Dae-Young Jung, Jun-Gyo In, Beom-Soo Lee, and Deok-Chun Yang * Korean Ginseng Center and Ginseng Genetic Resource Bank, Kyung Hee University, Yongin 449-701, Korea The medicinal plant Panax ginseng (P. ginseng) contains various phytosterols and bioactive triterpene saponins (ginsenosides). Squalene synthase catalyzes the first committed step in ginsenoside biosynthesis. Transgenic plants of P. ginseng were generated by introducing the squalene synthase gene derived from P. ginseng. Adventitious roots of the transgenic ginseng grew best in B5 medium, and 2 g of inoculum secured an optimal growth rate. Two phytohormones, indolebutyric acid and 1-naphtalene acetic acid, increased root growth and decreased ginsenoside production. Treatment with two selected elicitors, chitosan and jasmonic acid, and a precursor of the isoprenoid pathway, mevalonic acid, enhanced ginsenoside production and retarded ginseng growth rate. Keywords: Elicitor, Ginseng, Ginsenoside, Jasmonic acid, Squalene synthase This is an Open Access article distributed under the terms of the Cre- ative Commons Attribution Non-Commercial License (http://creativecom- mons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 11 Jan. 2010, Revised 26 Feb. 2010, Accepted 11 Mar. 2010