VmUGT88A65 and VmUGT88A66 orchestrate root development and pathogen resistance in tung tree via flavonoid and lignin glycosylation

Vernicia montana possesses a robust root system and exhibits high resistance to the soil-borne fungus Fusarium. The molecular mechanism underlying this resistance remains largely elusive. Here, we identified the species-specific UDP-glucosyltransferase coding genes VmUGT88A65 and VmUGT88A66 in V. montana through evolutionary analysis. These genes displayed exclusively root-specific expression patterns and were significantly upregulated upon infection with Fof-1. Transgenic tung trees overexpressing VmUGT88A65 and VmUGT88A66 exhibited a substantial increase in root index from 1.59 g to 2.16 g and enhanced resistance to Fof-1, which was associated with elevated levels of flavonoid and lignin glycosides. Conversely, RNAi-mediated suppression of VmUGT88A65 and VmUGT88A66 resulted in increased susceptibility to Fof-1, reduced root size, and decreased glycoside accumulation. In vitro and in vivo experiments further confirmed that VmUGT88A65 and VmUGT88A66 catalyze the glycosylation of specific compounds, producing flavonoid glycosides (N7G and Q7G) and lignin glycosides (CA4G and FA4G). Exogenous application of a combination of N7G and Q7G significantly inhibited Fof-1 mycelial growth and host infection in vitro. Additionally, CA4G and FA4G contributed to enhanced lignin deposition in roots, thereby strengthening the physical barrier against Fof-1. Our findings reveal a pathway through which VmUGT88A65 and VmUGT88A66 overexpression enhances the accumulation of flavonoid and lignin glycosides and promotes root growth, collectively contributing to improved disease resistance in tung trees.