Multiplex Approach of Metabolite and Transcript Profiling Identify a Biosynthetic Mechanism for Kayaflavone Biosynthesis in Torreya Grandis

Torreya grandis is a medicinal and edible food plant from southern China that is high in flavonoids and other bioactive compounds. Among these, Torreya grandis-enriched kayaflavone is a unique biflavone with potent antibacterial, antioxidant, and other health-promoting properties. However, the regulatory mechanisms directing kayaflavone biosynthesis in Torreya grandis remain unclear. Therefore, an integrated metabolite and transcript profiling of various Torreya grandis tissues was carried out. The results demonstrated a tissue-specific pattern in the kayaflavone content, with roots and kernels displaying the lowest levels and arils, leaves, and stems displaying the highest enriched content. Kyoto Encyclopedia of Genes and Genome (KEGG) analysis of different tissues revealed that differentially expressed genes were primarily enriched in the flavonoid biosynthesis pathway. Asides, a key apigenin 4’-O-methyltransferase for kayaflavone biosynthesis, TgOMT1, was annotated and characterized using weighted gene co-expression network analysis (WGCNA), RT-qPCR and enzyme assays. Additionally, transcription factors involved in TgOMT1 regulation, including MADS, HD-ZIP and ERF, were screened by co-expression assays, suggesting their roles in kayaflavone biosynthesis. These results elucidated the mechanisms underlying kayaflavone discrepancy in different tissues, providing a better insight on kayaflavone production in Torreya grandis and aiding future biotechnological attempts for valued medicinal production.