Hydrogen sulfide improves performance under suppressed photorespiration in Arabidopsis thaliana and orchestrates molecular reprogramming to alleviate stress

• Hydrogen sulfide (H 2 S) acts as a master regulator that enables Arabidopsis to tolerate the stress caused by suppressed photorespiration (NPC) due to high CO 2 environments. • The H 2 S protection is linked to a metabolic and molecular reprogramming, correcting the C/N elemental imbalance, restoring the profile of specific amino acids and regulating polyunsaturated fatty acids (PUFAs) accumulation which are critical for cell function. • H 2 S exerts its protective role via persulfidation at the posttranslational level, but also at the transcriptional level, specifically repressing hypoxia marker genes and negatively modulating the ABA signaling pathway controlling stomatal function under NPC. • This integrated study provides novel evidence positioning H 2 S as a key orchestrator of plant resilience that can be utilized in metabolic engineering strategies to enhance crop performance in future highCO 2 environments. High levels of atmospheric carbon dioxide result in suppression of plant photorespiration. The non-photorespiratory conditions (NPC) result in unbalancing the C/N metabolism, overproducing reactive oxygen species (ROS), and reducing stomatal activity. In plant stress responses, hydrogen sulfide (H 2 S) has been identified as an important signaling molecule through persulfidation of specific proteins. Previous works demonstrated that H₂S protects Arabidopsis thaliana against NPC-induced stress, and this work investigates the molecular basis of such protection. H₂S modulates a metabolic reprogramming influencing elemental homeostasis of C/N ratio, amino acids profile, central carbon metabolites and accumulation of polyunsaturated fatty acids (PUFAs). Persulfidation level under NPC was also restored after H₂S treatment. At the transcriptomic level, several well-known hypoxia marker genes, such as plant CYSTEINE OXIDASE 1 and 2 , ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR ERF71 AND ETHYLENE RECEPTOR 2 , are induced under NPC, and sulfide treatment decreases their expression levels to the ones in active photorespiration conditions (APC). H₂S also negatively regulates ABA signaling by targeting genes controlling ion transport and stomatal development which are involved in stomatal function. These integrated responses across metabolism, redox regulation and developmental programming emphasize the key contribution of H₂S to orchestrating plant adaptation to high CO₂ environments, positioning it as a master regulator that ensures plant resilience in the face of climate change.