Dose-dependent mitochondrial H 2 O 2  signaling drives toxicity or stress adaptation and longevity in fission yeast.
The spatiotemporal dynamics of hydrogen peroxide (H 2 O 2 ) signaling and its effects on gene expression and cell fitness remain unclear. Using fission yeast, we applied genetic tools to control and monitor intracellular H 2 O 2  levels. We expressed the H 2 O 2  biosensor HyPer7 in four subcellular compartments, overexpressed D-amino acid oxidase (Dao1) in specific locations to induce localized H 2 O 2  production, and modulated H 2 O 2  detoxification or sensing. H 2 O 2  concentrations showed 2- to 5-fold reductions across membranes, and D-amino acid treatments generated nanomolar H 2 O 2  levels in Dao1-expressing cells. Mitochondrial-targeted Dao1 produced H 2 O 2  fluxes capable of reaching the nucleus. While high mitochondrial H 2 O 2  disrupted mitochondrial morphology and respiration, lower levels triggered antioxidant defenses, enhancing stress resistance and longevity. These findings establish a quantitative framework for mitochondrial H 2 O 2  signaling and demonstrate that localized redox signals from mitochondria can either promote or impair cellular fitness depending on their intensity.
de Cubas L, Crevatin MF, Vega M, Boronat S, Ayté J, Hidalgo E