Abstract

Fusarium oxysporum f. sp. pseudostellariae (Fop) is the major causal agent of root rot in Pseudostellaria heterophylla . This study focused on VeA, a conserved pathogenicity regulator in Fop. RNA interference constructs targeting the Velvet domain (VeA-1) and nuclear localization signal (NLS) region (VeA-2) were generated to assess their effects on fungal growth, virulence and host responses. Phylogenetic and structural analyses showed that Fop VeA contains a canonical Velvet domain and NLS motif conserved across filamentous fungi. Silencing of VeA significantly impaired colony growth and conidiation, indicating its positive regulatory role in development. Pathogenicity assays revealed markedly reduced virulence of ΔVeA-1 and ΔVeA-2 strains, with alleviated root rot symptoms in P. heterophylla . Biochemical assays showed that wild-type infection induced strong antioxidant enzyme activities (peroxidase, catalase, superoxide dismutase), whereas these responses were attenuated under VeA silencing, corresponding to reduced oxidative stress. Reverse transcription-quantitative PCR confirmed that VeA modulates host defence gene expression ( PR2 , PR4 , PR5 ). Transcriptomic enrichment further indicated activation of immune-related pathways during infection. Collectively, VeA acts as a key regulator coordinating fungal development and virulence while indirectly manipulating host oxidative and immune responses, providing a potential molecular target for biological control of root rot in P. heterophylla .