Interactive effects of temperature and water activity on growth, mycotoxin production, and transcriptomic profiles of Aspergillus flavus, Aspergillus parasiticus, and Fusarium verticillioides.

Maize is frequently contaminated with aflatoxins (AFs) and fumonisins (FBs), posing a significant global food safety threat. Understanding how environmental factors regulate fungal toxigenesis under global warming is crucial. This study systematically investigated the in vitro stress responses of Aspergillus flavus, Aspergillus parasiticus, and Fusarium verticillioides (strains isolated from contaminated maize) across broad gradients of temperature (15-40 °C) and water activity (0.93-0.995 aw). Phenotypically, primary and secondary metabolism exhibited striking divergence: A. flavus grew optimally at 30 °C and 0.98 aw, yet intriguingly accumulated peak AFB2 specifically under severe drought stress (0.93 aw). A. parasiticus showed broad thermal adaptability for growth, but its AFB1 production was strictly confined to 25 °C. F. verticillioides maximized FB1 at 20 °C and 0.98 aw,. Transcriptomics revealed novel regularity underlying these patterns: under drought stress, A. flavus AFB2 biosynthesis uniquely decoupled from the classical aflM-dependent pathway via metabolic flux redirection; lepI was identified as an unprecedentedly strict temperature-dependent switch for A. parasiticus AFB1; and a FUM13-centric hub network coordinated FB1 synthesis in F. verticillioides. These findings provide a theoretical basis for developing targeted mycotoxin mitigation strategies under environmental factors change.