Transcriptomic Analysis Reveals Mechanisms Underlying the Inhibitory Effects of (E)-2-Heptenal on Spore Germination of Aspergillus Flavus

Plant volatile organic compounds are an abundant resource that can be used to explore natural gaseous fungicides. Recently, we found that (E)-2-heptenal, a green leaf volatile, could effectively inhibit the growth of Aspergillus flavus, showing promise for application as a biofumigant to prevent grain spoilage by A. flavus. In this study, the inhibitory effects of (E)-2-heptenal on A. flavus spore germination and mechanisms underlying these effects were investigated through morphological, biochemical, and transcriptomic analyses. The minimum inhibitory concentration and minimum fungicidal concentration of (E)-2-heptenal for spore germination of A. flavus were 4.0 and 6.0 µL/mL, respectively. (E)-2-heptenal treatment resulted in irregularly deformed, collapsed, and ruptured surface morphology of A. flavus spores, as well as destroyed cell wall integrity and reduced ergosterol content in A. flavus spores. Transcriptomic analysis revealed 4,312 differentially expressed genes in A. flavus spores exposed to (E)-2-heptenal, including 1,913 upregulated and 2,399 downregulated genes; these genes were mainly involved in ribosome biogenesis, cell cycle, linoleic acid metabolism, MAPK signaling, nucleoplasmic transport, meiosis, lipoic acid metabolism, DNA replication, and pyruvate metabolism pathways. (E)-2-heptenal can induce reactive oxygen species accumulation and mitochondrial dysfunction in A. flavus spores in a dose-dependent manner. Besides, DNA damage and autophagy was observed in (E)-2-heptenal-treated A. flavus spores with 4′,6-diamidino-2-phenylindole and monodansylcadaverine fluorescence staining. The findings of the present study provide insights into the underlying inhibitory mechanisms of (E)-2-heptenal on A. flavus spore germination.