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

Hydrogen peroxide (H 2 O 2 ) 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 H 2 O 2 at 10 mmol/L for 8 h to study the mechanism of how H 2 O 2 regulates leaf senescence. The data indicated that H 2 O 2 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. H 2 O 2 treatment also induced the accumulation of H 2 O 2 and malondialdehyde (MDA), decreased POD and SOD enzyme activities and inhibited H 2 S production by reducing the expression of LCD1/2 and DCD1/2. A correlation analysis indicated that H 2 O 2 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 H 2 S showed the highest load value followed by O 2 •- , H 2 O 2 , DCD1 , SAG15 , etc. Therefore, these findings provide a basis for studying the role of H 2 O 2 in regulating detached tomato leaf senescence and demonstrated that H 2 O 2 plays a positive role in the senescence of detached leaves by repressing antioxidant enzymes and H 2 S production.