Jasmonates mediate increased levels of ginsenosides in Panax Quinquefolius cambial meristematic cell cultures

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BACKGROUND: CMCs (cambial meristematic cells) are important resources for enhanced biotechnological production of plant secondary metabolites (SMs). However, CMC culture has not yet been established for American ginseng (Panax quinquefolius), an important source of ginsenosides, which are highly active SMs. Here, we investigated the molecular mechanisms involved in SMs' production in induced CMC and DDC (dedifferentiated cell) cultures through comparative biochemical, metabolomics, and transcriptome analyses. RESULTS: Relative to dedifferentiated cells (DDCs), CMCs showed significantly higher growth rates and content of ginsenosides (Rg1, Rd1, Re, and Rd), crude protein, fat, total sugar, and endogenous jasmonates (JA, MEJA, and JA-ILE). We identified 521 differential metabolites and 12,591 DEGs (differentially expressed genes). JA-related metabolic pathways, biosynthesis of SMs, and plant hormone signal transduction were significantly induced in CMCs compared to DDCs. Notably, most differential ginsenosides and flavonoids were up-regulated in CMCs. Key highly induced DEGs in the ginsenoside biosynthesis pathway, including the terpenoid pathway-related genes, cytochrome P450 family genes, and UDP-glucuronosyl/UDP-glucosyl transferases, were uncovered. Meanwhile, phytohormone, antioxidant enzyme, and transcription factors (TFs)-related candidate genes were also identified. It was noteworthy that most differentially expressed TFs (particularly EP2/ERF) were highly induced in CMCs compared to DDCs. CONCLUSIONS: Our results highlight that high levels of endogenous jasmonates promote the growth and synthesis of ginsenosides, flavonoids, and polysaccharides in American ginseng CMCs. Moreover, they provide fundamental bases for optimizing Panax spp. CMC cultures for sustainable industrial-scale production of ginsenosides.