Ethanol accumulation inhibited the growth of Saccharomyces cerevisiae during wine fermentation. Autophagy and the release of reactive oxygen species (ROSs) were also induced under ethanol stress. However, the relation between autophagy and ethanol stress was still unclear. In this study, expression of the autophagy genes ATG1 and ATG8 and production of ROS under ethanol treatment in yeast were measured. The results showed that ethanol stress very significantly induced expression of ATG1 and ATG8 genes and the production of peroxide hydrogen (H₂O₂) and superoxide anion (O₂·-). Moreover, the atg1 and atg8 mutants aggregated more H₂O₂ and O₂·- than the wild-type yeast. In addition, inhibitors of the ROS scavenging enzyme induced expression of the ATG1 and ATG8 genes by increasing the levels of H₂O₂ and O₂·-. In contrast, glutathione (GSH) and N-acetylcystine (NAC) decreased the ATG1 and ATG8 expression by reducing H₂O₂ and O₂·- production. Rapamycin and 3-methyladenine also caused an obvious change in autophagy levels and simultaneously altered the release of H₂O₂ and O₂·-. Finally, inhibitors of mitochondrial electron transport chain (mtETC) increased the production of H₂O₂ and O₂·- and also promoted expression levels of the ATG1 and ATG8 genes. In conclusion, ethanol stress induced autophagy which was regulated by H₂O₂ and O₂·- derived from mtETC, and in turn, the autophagy contributed to the elimination H₂O₂ and O₂·-.
Keywords: Autophagy; ethanol stress; fermentation; hydrogen peroxide; reactive oxygen specie; superoxide anion.