Exploitation of Host-Derived N-Feruloylputrescine by Fusarium graminearum Promotes DON Biosynthesis and Wheat Rachis Colonisation.

Plants reprogramme their metabolism upon pathogen attack, producing compounds that can either enhance immunity or be exploited by pathogens. Metabolomic profiling of wheat during Fusarium graminearum infection revealed pronounced accumulation of phenolamides, driven by activation of their biosynthetic pathways. Notably, exogenous N-feruloylputrescine (Ferput), a representative phenolamide, enhanced resistance to wheat stripe rust, powdery mildew and rice blast but increased susceptibility to Fusarium head blight. Ferput inhibited fungal infection in the lemma while promoting rachis colonisation, indicating pathogen- and tissue-specific effects. Mechanistic analyses showed that Ferput stimulates deoxynivalenol (DON) biosynthesis by inducing TRI gene expression, toxisome formation and DON-associated cellular differentiation, underlying the shift from lemma resistance to rachis susceptibility. Together, these findings highlight the context-dependent roles of phenolamide in plant-pathogen interactions and suggest that, under specific pathological contexts, defence-associated metabolites can be exploited by pathogens to enhance their virulence. This insight underscores the necessity of considering the dual functional roles of plant metabolites when engineering broad-spectrum disease resistance.