Aflatoxin production of Aspergillus flavus is affected by abiotic factors such as temperature, water activity, oxidative stress, etc. These factors likely affect different metabolic pathways and result in altered aflatoxin production. Aflatoxin was determined in liquid media at 28 °C, solid media at 28 °C and solid media at 37 °C. The proteomic method was used to elucidate the mechanism of aflatoxin production in A. flavus in liquid media at 28 °C, solid media at 28 °C and solid media at 37 °C. Potential factors affecting aflatoxin production were found by GO and KEGG analysis. A. flavus produces more aflatoxin at 28 °C compared to 37 °C. Our study also found that A. flavus cultured on solid media produced more aflatoxin than in liquid media. In this study, we identified 5029 proteins from A. flavus NRRL3357, in which 1547 differential proteins were identified between liquid media and solid-state media, while 546 differential proteins were identified between 28 °C and 37 °C. Biological informatics analysis showed that these differential proteins were widely involved in a variety of biological processes, molecular functions, and cellular components, and were associated with multiple metabolic pathways. Compared to the liquid media, extracellular hydrolase for nutrient uptake and proteins related to sclerotia development were differentially expressed on solid media (p < 0.05). Enzymes involved in oxidative stress showed significantly down-regulated in liquid media and up-regulated at 28 °C (p < 0.05). Furthermore, our research also revealed aflatoxin synthesis is a complex process that is affected by a variety of factors such as nutrient uptake, oxidative stress, sclerotia development, G protein signaling pathways and valine, leucine and isoleucine degradation, and a speculative model summarizing the regulation of aflatoxin biosynthesis in A. flavus is presented.
Keywords: Aflatoxin; Aspergillus flavus; G protein signaling pathways; Oxidative stress; Proteomics.
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