Transcriptome and metabolome reveal the accumulation of secondary metabolites in different species of Dioscorea.

BACKGROUND

The genus Dioscorea is traditional Chinese medicine producing a variety of pharmacological active substances especially saponins. In our study, the secondary metabolism of Dioscorea zingiberensis and D. opposita that have significantly different saponin contents were investigated.

RESULT

The saponin content was significantly different between two species. KEGG pathway enrichment analysis of transcriptomic data revealed significant differences between the two species in several metabolic pathways, including secondary metabolite biosynthesis, phenylpropanoid biosynthesis, starch and sucrose metabolism, photosynthesis, flavonoid biosynthesis, and steroid biosynthesis. Notably, 28 differentially expressed genes (DEGs) were linked to steroid biosynthesis. Through further metabolome analysis, we detected a total of 1 010 metabolites, and 212 (52 upregulated and 160 downregulated) differential metabolites (DAMs) were screened. The DAMs were mainly enriched in biosynthesis of secondary metabolites (32), amino acids (17), carbon metabolism (10), pentose phosphate (7), phenylalanine metabolism (6), and steroid (2). The combined analysis of transcriptome and metabolome found that terpenoid backbone biosynthesis, flavonoid biosynthesis and steroid biosynthesis were significantly enriched. In addition, we screened three candidate glycosyltransferase genes involved in dioscin biosynthesis.

CONCLUSIONS

The integration of transcriptome and metabolome analyses revealed a strong correlation between metabolite contents and gene expression. Three genes, J5N97_024139 (sterol 3-beta-glucosyltransferase 1, UGT80A2), J5N97_022450 (sterol 3-beta-glucosyltransferase 2, UGT80B1) and J5N97_004795 (UDP-rhamnose transporter 1, URT1), were significantly positively correlated with dioscin biosynthesis. These results provide valuable data for the study of secondary metabolites, particularly saponins, and lay a solid foundation for breeding ideal Dioscorea plants.