Transporters govern weak acid adaptation, ochratoxin a biosynthesis, and host colonization in aspergillus...

The mechanisms underlying fungal resistance to weak acid preservatives remain poorly understood, particularly regarding the roles of membrane transporters. Using transcriptomic analysis of Aspergillus westerdijkiae exposed to benzoic acid, we identified three transporters potentially involved in weak acid adaptation: the polyamine transporter AwPat1, the amino acid permease AwAap1, and the major facilitator superfamily (MFS) transporter AwMfs1. Targeted deletion of AwPat1 or AwAap1 disrupted cellular morphology, causing collapsed hyphae, reduced conidiation, and arrested sclerotial maturation, whereas the ΔAwMfs1 mutant maintained normal vegetative growth. Contamination assays across postharvest food matrices (sorghum grains, grapes, and pears) showed that all three transporters are required for substrate colonization and mycotoxin production under preservative stress. Notably, despite normal growth under standard conditions, the ΔAwMfs1 strain exhibited an acid-specific sensitivity. Although baseline colonization varied among the deletion strains, weak acid application severely restricted their growth on the tested commodities and completely inhibited ochratoxin A (OTA) biosynthesis. Quantitative analysis confirmed that each transporter deletion reduced OTA accumulation, with the greatest reduction occurring in the ΔAwPat1 strain. These physiological data indicate that AwPat1 and AwAap1 govern both structural development and general stress tolerance, whereas AwMfs1 functions specifically in acid adaptation and postharvest colonization. Overall, our work connects membrane transport directly to preservative survival and toxigenesis, identifying practical molecular targets to enhance preservative efficacy and mitigate mycotoxin contamination in stored foods.