Hydrogen Peroxide Promotes Tomato Leaf Senescence by Regulating Antioxidant System and Hydrogen Sulfide Metabolism

Hydrogen peroxide (H₂O₂) is relatively stable among ROS (reactive oxygen species) and could act as a signal in plant cells. In the present work, detached tomato leaves were treated with exogenous H₂O₂ at 10 mmol/L for 8 h to study the mechanism of how H₂O₂ regulates leaf senescence. The data indicated that H₂O₂ treatment significantly accelerated the degradation of chlorophyll and led to the upregulation of the expression of leaf senescence-related genes (NYC1, PAO, PPH, SGR1, SAG12 and SAG15) during leaf senescence. H₂O₂ treatment also induced the accumulation of H₂O₂ and malondialdehyde (MDA), decreased POD and SOD enzyme activities and inhibited H₂S production by reducing the expression of LCD1/2 and DCD1/2. A correlation analysis indicated that H₂O₂ was significantly and negatively correlated with chlorophyll, the expression of leaf senescence-related genes, and LCD1/2 and DCD1/2. The principal component analysis (PCA) results show that H₂S showed the highest load value followed by O₂^•-, H₂O₂, DCD1, SAG15, etc. Therefore, these findings provide a basis for studying the role of H₂O₂ in regulating detached tomato leaf senescence and demonstrated that H₂O₂ plays a positive role in the senescence of detached leaves by repressing antioxidant enzymes and H₂S production.