Transcriptomics and functional characterization identify CYP73A16 as a key regulator of flavonoid biosynthesis in mulberry leaves

BACKGROUND: Mulberry cultivars are well known for their flavonoid content. However, flavonoid content and the key genes involved in flavonoid biosynthesis in mulberry cultivars Zhong Shen 1 Hao (ZS) and Lv Shenzi (LSZ) are not well documented. This study aimed to analyze the flavonoid content and the key genes involved in flavonoid biosynthesis in ZS and LSZ cultivars. In this study, biochemical, transcriptomic, and functional analyses via virus-induced gene silencing (VIGS) were performed to analyze flavonoid content and key genes involved in flavonoid biosynthesis in ZS and LSZ. RESULTS: The content of flavonoids in LSZ is higher than in ZS, increasing by 38.1% compared to ZS. Transcriptome analysis identified 1938 differentially expressed genes (DEGs), with 1124 downregulated and 814 upregulated, and 14 DEGs were identified as key genes significantly enriched in flavonoid biosynthesis. Transient silencing of MaCYP73A16 notably decreased not only the expression of downstream genes, including MaCYP73A16, MaLAR, MaCHS, MaCYP93B1, and MaCYP98A2, but also reduced flavonoid content, with peak silencing efficiency observed on the ninth day, underscoring the impact of silencing MaCYP73A16 on other genes involved in the flavonoid biosynthesis pathway. CONCLUSION: This study provides a fundamental overview of flavonoid biosynthesis in LSZ and ZS and the key genes involved, which will help facilitate a comprehensive analysis of this pathway and provide significant insight into the large-scale biosynthesis of medicinal flavonoids, thereby improving flavonoid content in these cultivars.