Integrated transcriptomic and metabolomic analysis reveal the molecular and metabolic basis of flavonoids in Chinese sour jujube fruits in different harvest times

Chinese sour jujube (Ziziphus jujuba var. spinosa (Bunge) Hu ex H. F. Chow) is one of woody plant with the same origin of medicine and food. Specialized metabolites including flavonoids are mainly distributed in its active ingredient, but the composition and biosynthesis mechanism of flavonoids in different harvest times are still unclear. Hence, the accumulation of flavonoids in Chinese sour jujube fruits from five harvest times was investigated, using a combined metabolomics and transcriptomics approach in this study. And a total of 1539 differentially accumulated metabolites (DAMs) and 11592 differentially expressed genes (DEGs) were identified. The flavonoid, flavone, and flavanols biosynthtic pathways were significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs and DAMs. Furthermore, a comprehensive regulatory network was built for flavonoids biosynthesis and it was discovered that one FLS gene, and one NAC transcription factors (TFs) with a high connection with flavonoids biosynthesis by weighted gene co-expression network analysis (WGCNA). Finally, RT-qPCR analysis of 15 flavonoid biosynthesis-related key genes validated the transcriptome sequencing data. This study provides a basis for further research and utilization of flavonoids in Chinese sour jujube and which is beneficial to the metabolic engineering of flavonoids.