Molecular Mechanism of p-Hydroxybenzoic Acid in Promoting the Pathogenicity of Fusarium oxysporum: A Multi-Omics Study Based on Transcriptome, Metabolome, and HPLC-MS Analysis

p-Hydroxybenzoic acid (p-HBA), a crucial component of plant root exudates, directly or indirectly influences the incidence of plant root rot in soil. To further elucidate the mechanism by which p-HBA enhances the pathogenicity of Fusarium oxysporum , the primary pathogen responsible for plant root rot, transcriptomic, metabolomic, and HPLC-MS analyses were conducted to investigate the relationships among mycotoxin production, differential metabolites, and gene expression in F. oxysporum under stress induced by different concentrations of p-HBA. The results demonstrated that an optimal concentration of p-HBA significantly promoted the secretion of beauvericin (BEA) by F. oxysporum and led to notable enrichment of key metabolic pathways and genes associated with conidiospore formation. Specifically, treatment with 5 mmol·L ^-1 p-HBA increased BEA secretion by 4.8-fold compared with that of the control. In contrast, the addition of p-HBA inhibited fusaric acid(FSA) production. Metabolomic analysis revealed that L-phenylalanine, a precursor of BEA biosynthesis, was the most significantly differentially accumulated metabolite following p-HBA treatment, further confirming the effect of p-HBA on BEA production. Transcriptomic analysis indicated that treatment with 5 and 7.5 mmol·L ^-1 p-HBA significantly enriched metabolic pathways and genes related to amino acid metabolism, including phenylalanine, tyrosine, arginine, proline, and lysine metabolism, all associated with conidiospore formation. These findings suggest that the primary mechanism by which p-HBA enhances the pathogenicity of F. oxysporum is by promoting conidiospore production and BEA synthesis.