Harnessing Jasmonate Pathways: PgJAR1’s Impact on Ginsenoside Accumulation in Ginseng

Ginsenosides, the most active components in <i>Panax ginseng</i>, exhibit pharmacological and therapeutic properties but are limited by their low abundance. Jasmonates (JAs), a class of stress-induced phytohormones, are integral in modulating plant defense responses and the biosynthesis of secondary metabolites, including ginsenosides. Jasmonoyl-isoleucine (JA-Ile), the primary bioactive JA compound, is biosynthesized by JA-Ile synthase 1 (JAR1). In this study, we cloned the 1555 bp <i>PgJAR1</i> gene from ginseng roots and analyzed its structure, enzyme activity, and expression pattern. The PgJAR1 protein encompasses all the hallmark elements characteristic of the GH3 family. It exhibits N/C-terminal domains analogous to ANL, three ATP/AMP-binding motifs, and distinct secondary structures: an N-terminal beta-barrel with beta-sheets and alpha-helices, and a C-terminal beta-sheet surrounded by alpha-helices, similarly to AtGH3.11/AtJAR1. The recombinant PgJAR1 enzyme expressed in <i>Escherichia coli</i> BL21 specifically catalyzed jasmonic acid (JA) to JA-Ile. <i>PgJAR1</i> is predominantly expressed in leaves and is upregulated by MeJA treatment. Moderate transient overexpression of <i>PgJAR1</i> promoted the biosynthesis of both JA-Ile and ginsenosides, highlighting the crucial role of <i>PgJAR1</i> in JA-Ile biosynthesis and its positive impact on ginsenoside accumulation. Nevertheless, elevated JA-Ile levels can impede cellular growth, reducing ginsenoside production. Consequently, balancing JA-Ile biosynthesis through <i>PgJAR1</i> expression is essential for optimizing ginseng cultivation and enhancing its medicinal properties. Modulating endogenous JA-Ile levels offers a strategy for increasing ginsenoside production in ginseng plants.