Transcriptomic analysis shows the antifungal mechanism of honokiol against Aspergillus flavus

Plant-derived substances as antifungal agents have received considerable attention in recent years to reduce the use of chemical fungicides in food preservatives. In this study, honokiol, a type of phenolic compound in Magnolia officinalis, was found to inhibit spore germination and mycelia growth of Aspergillus flavus at 100 μg/mL. In addition, a pathogenicity assay showed that honokiol had potent antifungal activity against A. flavus in corn flour by suppressing conidia production. Fluorescence staining, transmission electron microscopy and biochemical assays were performed to explore its possible inhibition mechanisms against A. flavus. The results showed that the destructive effect of honokiol on A. flavus appeared to be related to increased plasma membrane permeability, the inhibition of ATPase activity, mitochondrial dysfunction and the accumulation of reactive oxygen species. Furthermore, a transcriptomic analysis showed that honokiol treatment resulted in 1578 different expressed genes. Gen Ontology and Kyoto Encyclopedia of Genes and Genomes analysis revealed that some genes of A. flavus related to spore development, integrity of the cell wall and membrane, oxidative stress and energy metabolism were significantly downregulated. In addition, RNA-seq results were validated by quantitative real-time polymerase chain reactions. Our finding enhanced the understanding of the antifungal activity of honokiol and underlying mechanisms of action at the molecular level, supporting honokiol as a potential agent in preventing contamination by A. flavus.