Transcriptome and metabolome combined analysis of the molecular mechanisms underlying dendrobine biosynthesis in Dendrobium nobile.

Dendrobium nobile (Dendrobium nobile Lindl.) is an epiphytic perennial herbaceous medicinal plant of the genus Dendrobium in the family Orchidaceae, which has important pharmacological effects, and its medicinal value mainly stems from the active ingredient dendrobine contained in D. nobile. It was found that dendrobine is a terpenoid or sesquiterpenoid alkaloid, which is mainly biosynthesized through the terpenoid skeleton. The study aimed to explore the differences in the biosynthesis of dendrobine in D. nobile at the transcriptome and metabolome levels in the two periods, and to clarify the main pathways related to the biosynthesis of dendrobine in D. nobile, to provide scientific evidence for the study of the biosynthesis of dendrobine.In this study, we revealed the key genes and metabolic pathways of dendrobine biosynthesis in D. nobile by combined transcriptome and metabolome analysis. A total of 29,043 genes were obtained from RNA sequencing, and 25,772 genes were obtained through quality control, filtering, and de-hybridization. and A total of 2,075 DEGs were screened out, of which 1,229 genes were up-regulated and 846 genes were down-regulated. A total of 7821 metabolites were detected by metabolomic analysis, including 20 terpenoids, including 6 sesquiterpenes, 1 polyterpene, 2 diterpenes, 4 monoterpenes, 2 triterpenes, and 5 other terpenes, and a total of 383 DEMs were identified, of which 163 metabolites were up-regulated and 220 were down-regulated. In this study, we analyzed the differences in dendrobine between the two samples and found that the dendrobine content was significantly higher in the young shoot stage than in the robust period, and the accumulation trend was synchronized with the expression of key genes for terpene skeleton synthesis. Metabolome analysis revealed that these differential metabolites were mainly concentrated in terpenoids, sesquiterpenoids, and organic nitrogen compounds. Transcriptome analysis revealed that the accumulation of sesquiterpenoids was correlated with the high expression of FDPS and GGPPS1, among others, a phenomenon that suggests that these genes play a key role in regulating the conversion of FPP to sesquiterpenoid products, thereby affecting the synthesis efficiency of dendrobine. KEGG enrichment analysis revealed significant activation (p < 0.05) of the terpene skeleton biosynthesis pathway and cross-regulation with the phenylpropane biosynthesis pathway. The phenylalanine deaminase (PAL) gene may be involved in the late modification of dendrobine by providing phenylpropane derivatives during the juvenile shoot stage.This study provides new insights into the biosynthesis of dendrobine in D. nobile and provides some theoretical basis for the subsequent biosynthesis of dendrobine. By integrating transcriptomic and metabolomic data, this study revealed the key genes and metabolic pathways of dendrobine biosynthesis and provided a scientific basis for optimizing the synthesis efficiency of dendrobine and developing developmental-stage-based precision harvesting technology.