VfUGT87H9 Enhances Fusarium Resistance in Vernicia fordii via Myricetin Glucosylation‐Mediated Flavonoid Metabolism

Plant uridine diphosphate-dependent glycosyltransferases (UGTs) play a key role in plant growth and defense mechanisms. Tung oil tree (Vernicia fordii), suffers from disease caused by Fusarium oxysporum f. sp. Fordiis (Fol). However, little is known about how to enhance the resistance mechanism. In this study, we observed significant enrichment of flavonoid biosynthesis pathway in V. fordii roots following Fol infection, including myricetin-glucoside and kaempferol-glucoside. Based on transcriptomic analysis, we screened 11VfUGTs showing elevated expression in response to Fol infection. Through correlation analysis (Pearson's r) between flavonoid metabolite level and 11VfUGTs transcription levels, we discovered that increased flavonol glycoside accumulation post-infection was associated with VfUGT87H9 activity. Furthermore, the VfUGT87H9 gene exhibited strong root-specific expression and rapid transcriptional induction upon Fol challenge. In vitro enzymatic assays confirmed VfUGT87H9's ability to catalyze myricetin glucosylation, producing myricetin-glucoside. Transgenic plants overexpressing VfUGT87H9 demonstrated enhanced pathogen resistance compared to control plants, with OE-VfUGT87H9 roots accumulating significantly higher myricetin-glucoside level. In vitro assays showed that myricetin-glu inhibits mycelial growth and host infection by Fol. Our findings established VfUGT87H9 as a flavonoid glucosyltransferase that positively regulates plant disease resistance by maintaining flavonol glycosides homeostasis. This study advances our understanding of flavonoid-mediated plant-pathogen interactions and metabolic defense strategies.