Transcriptomics and metabolomic profiling identify molecular mechanism for Aspergillus flavus infection in grain

Aspergillus flavus is a ubiquitous saprophyte and opportunistic fungal pathogen with worldwide distribution, which causes diseases commonly in agricultural commodities and seriously threatens food security and human health. In this study, we try to reveal the mechanisms of A. flavus infection in grain from the perspective of apparent changes in physicochemical properties, microscopic structure, and ultrastructural changes at transcriptome-metabolomics levels. The results showed that the A. flavus infection included the preinfection (1-3 days) and postinfection period (4-7 days). The downregulated expression of creA promoted the cellulase expression and initiated infection. The metabolite oleic acid promoted infection as a nutrient carbon source and energy source. Then the entry of acetate units into the aflatoxin synthesis pathway was inhibited, whereas aflH, hypD, and hypB were significantly upregulated (p < .05) to stimulate the aflatoxin synthesis to complete the infection on the surface. During the postinfection period, the upregulation of aflS and other toxin-producing regulatory genes accelerated aflatoxin synthesis and completed the internal infection. At the same time, the upregulation of vitamin B-6 and allysine involved in amino acid metabolism, and galactose 1-phosphate involved in energy metabolism ensured the production of acetyl-CoA and the energy supply for A. flavus infection. The research findings highlight the underlying mechanisms of A. flavus infection at the transcriptome-metabolomics levels, which is important for developing effective strategies to prevent postharvest contamination.