Overexpression of PgSQS1 Increases Ginsenoside Production and Negatively Affects Ginseng Growth Rate in Panax ginseng

Abstract

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.

Insilico profiling of microRNAs in Korean ginseng (Panax ginseng Meyer)

“…Genes such as 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), farnesyl diphosphate synthase (FPS), geranyl-diphosphate synthase, squalene synthase, and squalene epoxidase (SE) were reported as putative ginsenoside pathway genes [27], and hydroxylation by cytochrome P450 and glycosylation mediated by UDP-glycosyltransferases lead to synthesis of various ginsenosides. Overexpression of P. ginseng squalene synthase was shown to increase the ginsenoside production [50]. These putative ginsenoside pathway genes were predicted as the miRNA targets, especially SE targeting miR854b and miR854c.…”

Biosynthesis and biotechnological production of ginsenosides

“…Overexpression of PgSS1 in P. ginseng caused 1.6-to 3-fold increase of total ginsenosides and 2-fold increase of phytosterols in transgenic adventitious root, accompanied by the upregulation of downstream enzymes such as SE, β-AS, and CAS Shim et al, 2010). The 2-fold reduction of squalene contents in the roots might be due to the rapid flux intermediates toward phytosterols .…”

Triterpenoid Biosynthesis and Engineering in Plants

“…Despite the improved productivities per unit weight, the transgenic plants sometimes showed growth inhibition (Masferrer et al, 2002; Manzano et al, 2004; Shim et al, 2010), probably caused by metabolic imbalances. In fact, co-overexpression of FPS and the HMGR catalytic domain alleviated the growth inhibition caused by the individual overexpression of FPS or the HMGR catalytic domain (Manzano et al, 2004).…”

“…In plants, overexpression of 3-hydroxy-3-methylgulutaryl-CoA reductase (HMGR), FPP synthase (FPS), and squalene synthase in the isoprenoid pathway has been attempted to increase triterpenoid productivity (Chappell et al, 1995 ; Schaller et al, 1995 ; Harker et al, 2003 ; Lee et al, 2004 ; Seo et al, 2005 ; Hey et al, 2006 ; Muñoz-Bertomeu et al, 2007 ; Lu et al, 2008 ; Kim et al, 2010 ). Despite the improved productivities per unit weight, the transgenic plants sometimes showed growth inhibition (Masferrer et al, 2002 ; Manzano et al, 2004 ; Shim et al, 2010 ), probably caused by metabolic imbalances. In fact, co-overexpression of FPS and the HMGR catalytic domain alleviated the growth inhibition caused by the individual overexpression of FPS or the HMGR catalytic domain (Manzano et al, 2004 ).…”