Overexpression of the squalene epoxidase gene ( PgSE1 ) resulted in enhanced production of ginsenosides and phytosterols
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Plant Biotechnology Reports https://doi.org/10.1007/s11816-020-00643-4
ORIGINAL ARTICLE
Overexpression of the squalene epoxidase gene (PgSE1) resulted in enhanced production of ginsenosides and phytosterols in transgenic ginseng Jung Yeon Han1 · Hye‑Jeong Jo1 · Yong Eui Choi1 Received: 21 August 2020 / Accepted: 16 September 2020 © Korean Society for Plant Biotechnology 2020
Abstract Squalene epoxidase (also called squalene monooxygenase) catalyses the conversion of squalene into 2,3-oxidosqualene by epoxidation and is regarded as the rate-limiting enzyme for sterol and saponin biosynthesis. However, the role of the squalene epoxidase gene in saponin biosynthesis in plants is not yet well understood. Here, we investigated the effects of overexpression of a Panax ginseng squalene epoxidase gene (PgSE1) on the production of phytosterols and ginsenoside saponins in ginseng adventitious roots. For the functional complementation test, the two squalene epoxidase sequences (PgSE1 and PgSE2) of P. ginseng were expressed in a yeast erg1 mutant (ergosterol auxotroph). The yeast mutant expressing PgSE1 or PgSE2 can restore growth on medium lacking ergosterol. Transgenic ginseng roots overexpressing the PgSE1 gene were constructed by Agrobacterium-mediated genetic transformation. The transgenic ginseng roots resulted in the enhanced production of both ginsenosides (ginsenoside Rg1, Re, Rf, Rc, Rb1, Rb2, and Rd) and phytosterols (campesterol, stigmasterol, and β-sitosterol). qPCR analysis revealed that overexpression of PgSE1 in transgenic ginseng roots clearly enhanced the expression of dammarenediol-II synthase (PgDDS) and cycloartenol synthase (PgPNX), which are key enzymes for ginsenoside and phytosterol biosynthesis in P. ginseng. This result indicates that the P. ginseng squalene epoxidase gene (PgSE1) encodes an efficient enzyme responsible for not only phytosterol production but also ginsenoside production in P. ginseng. Keywords Panax ginseng-squalene epoxidase · Triterpene · Phytosterol · Genetic transformation Abbreviations RT-PCR Reverse transcription-PCR qPCR Quantitative real-time PCR MS Murashige and Skoog IBA Indolebutyric acid PgSE1 Panax ginseng Squalene epoxidase 1
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11816-020-00643-4) contains supplementary material, which is available to authorized users. * Yong Eui Choi [email protected] 1
Division of Forest Resources, College of Forest and Environmental Sciences, Kangwon National University, Chunchon 200‑701, Republic of Korea
Introduction Panax species are well-known medicinal plants, belonging to the family Araliaceae (Shibata 2001; Coleman et al. 2003). The major medicinal components responsible for the pharmacological activities of Panax species are triterpene saponins called ginsenosides (Vogler et al. 1999). Ginsenosides have various biological effects and have high medicinal value (Briskin 2000; Shibata 2001; Park et al. 2005). Naturally, the accumulation of ginsenosides in ginseng pl
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