Apoptosis is a regulated form of cell death crucial for development and homeostasis in metazoans. In yeast, apoptosis can be induced by glutathione depletion, low doses of H₂O₂, or mutations in CDC48 or expression of mammalian Bax. Oxygen radicals accumulate in yeast cells during apoptosis, suggesting their role in the process. The study shows that ROS are essential for the apoptotic phenotype in yeast, and their accumulation is a key event in the ancestral apoptotic pathway. The presence of ROS in yeast cells indicates that apoptosis may have evolved before the divergence of fungi and metazoans. The study also demonstrates that the expression of Bax in yeast leads to ROS accumulation, which is suppressed by Bcl-X_L. Cycloheximide prevents apoptosis by inhibiting protein synthesis, indicating the involvement of cellular metabolism in the process. The study further shows that yeast lacking glutathione exhibit apoptotic markers, and that ROS scavengers or anaerobic conditions can suppress apoptosis. These findings suggest that ROS play a central role in yeast apoptosis, and that the mechanisms involved are conserved across species. The study highlights the importance of ROS in the regulation of apoptosis and provides insights into the evolutionary origins of this process.Apoptosis is a regulated form of cell death crucial for development and homeostasis in metazoans. In yeast, apoptosis can be induced by glutathione depletion, low doses of H₂O₂, or mutations in CDC48 or expression of mammalian Bax. Oxygen radicals accumulate in yeast cells during apoptosis, suggesting their role in the process. The study shows that ROS are essential for the apoptotic phenotype in yeast, and their accumulation is a key event in the ancestral apoptotic pathway. The presence of ROS in yeast cells indicates that apoptosis may have evolved before the divergence of fungi and metazoans. The study also demonstrates that the expression of Bax in yeast leads to ROS accumulation, which is suppressed by Bcl-X_L. Cycloheximide prevents apoptosis by inhibiting protein synthesis, indicating the involvement of cellular metabolism in the process. The study further shows that yeast lacking glutathione exhibit apoptotic markers, and that ROS scavengers or anaerobic conditions can suppress apoptosis. These findings suggest that ROS play a central role in yeast apoptosis, and that the mechanisms involved are conserved across species. The study highlights the importance of ROS in the regulation of apoptosis and provides insights into the evolutionary origins of this process.