Endogenous ascorbic acid delays ethylene-induced leaf senescence in Arabidopsis thaliana

Leaf senescence is an important event in the plant life cycle. Ethylene and ascorbic acid (AsA) both regulate the leaf senescence process. The role of endogenous AsA in ethylene-induced leaf senescence was explored in two independent endogenous AsA changing Arabidopsis thaliana mutants. The line vtc2-1 with a single base change in VTC was AsA-deficient mutant; the GLDH-overexpressing line (GLDHOE) driven by the CaMV 35S promoter was AsA-overaccumulating mutant. After spraying 600 μM ethephon for 6 d, vtc2-1 showed the most serious leaf chlorosis, reactive oxygen species (ROS) accumulation, chlorophyll breakdown, Rubisco degradation, and had the highest expression level of senescence-associated genes (SAGs), such as SAG12, SAG13, SAG20, and SAG21 among the three lines. In contrast, GLDHOE maintained the highest photosynthetic pigments contents, Rubisco content, antioxidant capacity, and the lowest expression of SAG2, SAG20, and SAG21 among the three lines. Taken together, we conclude that endogenous AsA can delay ethylene-induced senescence by scavenging ROS and inhibiting SAGs expression.