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Proteomic Profile of Aspergillus flavus responses to oxidative stress


<div>Aflatoxin production by <em>A. flavus</em> and related species of fungi is regulated in concert with other secondary metabolites, developmental processes, and stress-responsive enzymes in response to environmental stress. Specifically, oxidative stress has been shown to be a pre-requisite and stimulator of aflatoxin production. This is of particular interest given the observation that drought stress results in compromised host resistance to aflatoxin contamination, and that drought stress results in the accumulation of ROS in host plant tissues. The objectives of this study were to use proteomics to provide insights into the pathogen responses to H<sub>2</sub>O<sub>2</sub>-derived oxidative stress, and to identify potential biomarkers for fungal infection and targets for host resistance breeding. Three isolates, AF13, NRRL3357, and K54A with high, moderate, and no aflatoxin production, and cultured in medium supplemented with varying levels of H<sub>2</sub>O<sub>2</sub>, were examined using an iTRAQ approach. Overall, 1,173 proteins were identified of which 238 were found to be differentially expressed (DEPs). Observed DEPs encompassed metabolic pathways including antioxidants, carbohydrates, pathogenicity, and secondary metabolism. Increased lytic enzyme, secondary metabolite, and developmental pathway expression in AF13 was correlated with increased tolerance to oxidative stress, likely assisting in host plant infection and microbial competition. Elevated expression of energy and cellular component production in NRRL3357 and K54A implies a greater focus on oxidative damage remediation. These trends provide insights into important mechanisms relevant to host plant interactions under drought stress allowing for more targeted efforts in host resistance research.</div>