Transcriptomic profiling reveals MEP pathway contributing to ginsenoside biosynthesis in Panax ginseng

Area of Science:

• Plant biochemistry
• Metabolic engineering
• Genomics

Background:

• Panax ginseng is a renowned medicinal herb, with ginsenosides as its primary bioactive compounds.
• Ginsenoside synthesis is traditionally attributed to the mevalonate (MVA) pathway.
• Recent evidence suggests the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway also contributes to ginsenoside production in P. ginseng.

Purpose of the Study:

• To investigate and compare the gene expression characteristics of the MEP and MVA pathways in Panax ginseng.
• To identify key enzymes involved in ginsenoside biosynthesis through transcriptional analysis.
• To provide insights for synthetic biology approaches in ginsenoside metabolic regulation.

Main Methods:

• Deep RNA sequencing of ginseng root samples (1-5 years old) and different tissues of 5-year-old plants.
• De novo assembly of unigenes and identification of genes related to ginsenoside biosynthesis and both MEP and MVA pathways.
• Analysis of gene expression profiles and co-expression networks to determine pathway contributions and identify rate-limiting enzymes.

Main Results:

• A total of 48,165 unigenes were assembled, including 380 ginsenoside biosynthesis genes and all MEP/MVA pathway enzyme genes.
• MEP pathway gene transcript abundances were similar to the MVA pathway in ginseng roots but higher in leaves.
• The IspD enzyme was predicted as the rate-limiting enzyme in the MEP pathway.

Conclusions:

• The MEP pathway contributes comparably to the MVA pathway in ginseng roots but significantly more in leaves for ginsenoside biosynthesis at the transcriptional level.
• IspD is identified as a potential key enzyme for ginsenoside generation via the MEP pathway.
• These findings offer valuable information for future synthetic biology studies on ginsenoside metabolic regulation.