Transcriptional Regulatory Of Ginsenosides Synthesis In Cultivated Ginseng (Panax Ginseng C.A.Meyer) Of Different Growth Years

Ginseng(Panax ginseng C.A.Meyer),a perennial herb,is mainly found in northeastern China,southern Russia,and Korea.As a traditional Chinese medicinal herb,ginseng has great medicinal value and has been shown to have therapeutic effects on tumours,repair of the nervous system and antioxidant damage.Ginseng has many important secondary metabolites,such as saponins,polysaccharides,flavonoids,etc.Among them,ginsenosides are the most important medicinal active ingredient in ginseng and an important indicator of ginseng quality.Cultivated ginseng is domesticated from wild ginseng and is now widely cultivated in China.Numerous studies have shown that the ginsenoside content of cultivated ginseng varies with the growth period of ginseng,but the expression pattern of genes related to ginsenoside synthesis and their regulatory mechanisms are still unclear.With the elucidation of ginsenoside synthesis pathways by scholars at home and abroad,a large number of key enzymes and genes related to ginsenoside synthesis have been identified,which provides a theoretical basis for investigating the molecular regulation mechanism of ginsenoside synthesis.In this study,we used one-year-old,three-year-old,five-year-old and six-year-old cultivated ginseng as experimental materials,sequencing the amount of gene expression and determine the ginsenoside content of root,stem and leaf tissues respectively,and combined with differential expression analysis,differential alternative splicing analysis,and WGCNA to reveal the expression pattern and transcriptional regulation mechanism of ginsenoside synthesis genes,and to explore their effects on the ginsenoside content in different cultivated ginseng.Integrating the above analyses,the main results obtained in this study are as follows.(1)The ginsenoside content in cultivated ginseng was significantly influenced by the cultivation age.In the root tissues,the ginsenoside content increased with increasing cultivation years,while it decreased in the stem and leaf tissues.In general,the ginsenoside content also varied among different tissues,with the highest ginsenoside content in the leaves,followed by the roots and the lowest in the stems in the same growth year ginseng.(2)Differentially expressed genes(DEGs)in root,stem and leaf tissues were mainly enriched in MAPK signalling pathway,ABC transporter protein and sesquiterpene and triterpene synthesis pathways;the expression levels of saponin synthesis genes also differed significantly among cultivated ginseng tissues of different years of cultivation.The expression levels of saponin synthesis genes also differed significantly among cultivated ginseng plants,mainly including genes encoding enzymes such as HMGCS,HMGCR,SQE and UGTs.(3)By comparing the differential alternative splicing of ginsenoside synthesis genes among different cultivation years,it was found that genes encoding 10 enzymes in the ginsenoside synthesis pathway had a total of 48 differential alternative splicing events,with genes encoding enzymes isp D,SS,β-AS and DDS having a higher frequency of differential variable splicing events.(4)A weighted gene co-expression network analysis combining ginsenoside content and transcriptional data from ginseng roots,stems and leaves revealed that the expression of a large number of ginsenoside synthesis genes correlated highly with the expression of specific transcription factors in the modules related to ginsenoside content,especially the genes encoding UGTs,whose expression correlated extremely well with transcription factors such as MYB,ERF and WRKY.In summary,this study combined transcriptome data and ginsenoside content data to reveal the effect of cultivation years on the transcriptional regulation mechanism of ginsenoside content and genes related to ginsenosides synthesis,which provides a reference for systematically understanding the mechanism and regulatory network of ginsenoside synthesis,and lays a theoretical foundation for improving ginsenoside content through molecular breeding,as well as exploring the synthesis of triterpenoids in medicinal plants.It also opens up new ideas for the synthesis of triterpenoids in medicinal plants.