PoNoxA mediates the crosstalk between fungal immune signaling and antimicrobial metabolite biosynthesis to enhance pathogen defense and food preservation

ABSTRACT Reactive oxygen species (ROS) generation by NADPH oxidases (NOXs) are critical for fungal physiology, but their roles in coordinating fungal metabolic byproducts and chemical defense are poorly understood. Using oyster mushroom ( Pleurotus ostreatus ) as a model, this study investigated the distinct functions of two NOXs (PoNoxA and PoNoxB) in defense against brown blotch disease (BBD) pathogen Pseudomonas tolaasii . PoNoxA overexpression significantly enhanced BBD resistance, while its silencing increases susceptibility. Integrated metabolomic and transcriptomic analyses uncovered that PoNoxA specially upregulated organooxygen compounds, fatty acyls, and terpenoid biosynthesis pathways. This coordination triggered the accumulation of three antimicrobial metabolites, 3-octanone, 1-octen-3-ol, and (-)-dihydrocarveol. These metabolites exhibited potent broad-spectrum antibacterial activity in vitro, inhibiting 93.9–99.5% of P. tolaasii and 62.8–99.5% of Escherichia coli growth, with IC 50 values ranging from 3.6 to 5.5 mM. Furthermore, external application of these metabolites to postharvest bananas and peppers extends shelf life by 4–6 days without altering sensory quality. Our results identify PoNoxA as a key regulator that bridges fungal immune activation to the biosynthesis of antimicrobial metabolites, and demonstrate the potential of these naturally derived compounds as effective and sustainable candidates to synthetic preservatives for agricultural disease management and food safety applications.