Integrated transcriptomic and metabolomic analyses reveal the mechanism of hypoxia tolerance in Aspergillus chevalieri under controlled nitrogen atmosphere.

A controlled nitrogen atmosphere (CNA) is favorable for postharvest grain management in large-grain warehouses. Storage fungi with a high hypoxic tolerance pose a potential threat to the safe storage of grains under a CNA. In this study, CNA storage of wheat grain was simulated, and Aspergillus chevalieri was identified as the predominant storage fungus after a 30-day storage period. Under an atmosphere of 2% O2, A. chevalieri grows on agar plates with the same colony diameter as that under normoxic conditions. The dry weight of A. chevalieri mycelia grown in liquid culture under hypoxic conditions was reduced by 60.56% compared with that under normoxic conditions. Scanning electron microscopy revealed that A. chevalieri mycelia exposed to hypoxic stress were shriveled and wrinkled. The ergosterol content of A. chevalieri mycelia under hypoxic stress increased by 151.17% compared with the control group. Catalase and superoxide dismutase were significantly upregulated in A. chevalieri by hypoxic stress, whereas the levels of H2O2, superoxide anions, and ATP were considerably decreased. Transcriptomic analysis identified 1345 differentially expressed genes, primarily enriched in pathways related to longevity regulation, mitochondrial autophagy, amino acid metabolism, ubiquitination metabolism, coenzyme A biosynthesis and glycolysis. Metabolomic profiling further revealed 87 markedly altered metabolites primarily involved in starch and sucrose metabolism, arginine and proline metabolism, and lysine degradation. By integrating multi-omics data with physiological and biochemical analyses, this study systematically elucidates the hypoxia adaptation mechanism of A. chevalieri under CNA conditions, providing insights that may facilitate the prevention and control of hypoxia-tolerant storage fungi.