Abstract
Ozone induces the synthesis of phytohormones, including ethylene and salicylic acid (SA), and these phytohormones act as signal molecules that enhance cell death. However some studies have shown that these phytohormones can decrease the magnitude of ozone-induced cell death. Here, we studied the defensive roles of ethylene and SA against ozone. Unlike wild-type plants, Arabidopsis mutants deficient in ethylene-signaling (ein2) or SA-biosynthesis (sid2) exhibited visible leaf injury, indicating that these phytohormones can reduce ozone damage. Induction of glutathione synthetase (GSH2) expression and the enzymatic activity in ein2 and sid2 were lower than those in Col-0. Increases of glutathione occurred in Col-0 was also suppressed in ozone-exposed ein2 and sid2 mutants. Moreover, ozone-induced leaf damage observed in these mutants was mitigated by artificial complementation of glutathione. Our results suggest that ethylene and SA protect against ozone-induced leaf injury by increasing de novo biosynthesis of glutathione.
