The antifungal activity of o-vanillin against Aspergillus flavus via disrupting ergosterol biosynthesis and promoting oxidative stress, and an RNA-seq analysis thereof

Abstract

o-Vanillin is an effective plant-derived compound inhibiting the growth of Aspergillus flavus (A. flavus). In this study, o-vanillin disrupted the cell membrane of A. flavus via hindering K+ transport across plasma membrane, decreasing the content of lipid, ergosterol and trehalose, and inducing lipid peroxidation. The HOG pathway might be upregulated as the content of glycerol increased. Moreover, o-vanillin significantly promoted oxidative stress, as indicated by the accumulation of intracellular reactive oxygen species (ROS) and decreased activities of antioxidant enzymes (e.g. superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)). Finally, transcriptomic analysis was conducted to quantify the differentially expressed genes of A. flavus treated by o-vanillin. Consistent with the above phenotypic changes, genes involved in several biological pathways (ergosterol biosynthesis, osmotic stress, and oxidative stress response) were significantly regulated by o-vanillin. Real-time quantitative PCR (QRT-PCR) results showed that almost all enzymes participating in ergosterol biosynthesis were downregulated by o-vanillin. In addition, o-vanillin can effectively suppress the pathogenicity of A. flavus on peanut butter. This study provides a new evidence in the antifungal activity of o-vanillin against cell membranes of A. flavus, and will promote the application of o-vanillin into the preservation of grains and agricultural products.