Ginsenosides accumulation and related genes expression in different underground parts of Panax notoginseng during maturation stage

Ginsenosides, which mainly exist in rhizomes and roots of Panax notoginseng (Burk) F. H. Chen, exhibit various physiological functions and medicinal values. However, the accumulation process of ginsenosides in the rhizome, epidermis, and xylem of the main root is unknown. Herein, the temporospatial distribution and mechanism of variation of ginsenosides in the underground parts of three-year-old P. notoginseng were investigated. The results showed that the accumulation of ginsenosides in rhizomes accelerated from May. In 12-month growth stages (except May), the content of ginsenosides in the xylem and epidermis were higher than that in the rhizome. However, the ginsenosides in rhizomes increased rapidly, whereas the ginsenosides in the main root decreased from May to July. The expression levels of genes encoding squalene epoxidase, dammarenediol synthase, and uridine diphosphate-dependent glycosyltransferase (UGTPg1) in rhizomes were increased in May, whereas genes encoding squalene synthase, protopanaxadiol synthase, protopanaxatriol synthase, UGTPg45, and UGTPg29 were expressed at considerably increased levels in June. Distinct expression levels of genes related to ginsenoside biosynthesis were the main reasons for the temporospatial fluctuation of ginsenoside accumulation in the two tissues. weighted gene co-expression network analysis demonstrated that many transcripts regulated ginsenoside accumulation in underground tissues. These results provide essential data for farmers and processors participating in P. notoginseng cultivation and utilisation.