[Transcriptomics-based mining of key genes for biosynthesis of iridoid glycosides in Morinda officinalis]

In this study, Morinda officinalis roots(MG), stems(MJ), and leaves(MY) were used as test materials. The main iridoid glycosides in various tissues were analyzed qualitatively and quantitatively using high-performance liquid chromatography(HPLC). Simultaneously, combined with transcriptome data, metabolite and gene association analyses were conducted to identify key candidate genes in the iridoid glycoside biosynthetic pathway. The expression levels of these key candidate genes were further validated by fluorescence quantitative PCR(qRT-PCR). HPLC results indicated that the content of iridoid glycosides in MG and MJ was significantly higher than in MY, being approximately twice as much. Transcriptome sequencing revealed that 6 275, 10 108, and 7 330 differentially expressed genes(DEGs) were identified in the three comparative groups of MG vs MJ, MG vs MY, and MJ vs MY, respectively. Among the differential genes, 21 genes related to the iridoid glycoside biosynthetic pathway were annotated. Correlation analysis showed that the DXS, IDI, GES, 10-HGO, and IS genes were positively correlated with the content of iridoid glycosides(r>0.8), suggesting that these five genes are likely key candidates in the iridoid glycoside synthesis process. The results of qRT-PCR confirmed that the expression levels of these five key candidate genes in different tissues were consistent with the transcriptome data. In conclusion, this study provides an important theoretical foundation and research base for the in-depth exploration of the molecular mechanisms underlying the biosynthesis and regulation of iridoid glycosides in M. officinalis, as well as valuable insights for the cultivation and production of high-quality M. officinalis medicinal materials.