Ethylene and salicylic acid control glutathione biosynthesis in ozone‐exposed Arabidopsis thaliana

Abstract

Ozone produces reactive oxygen species and induces the synthesis of phytohormones, including ethylene and salicylic acid. These phytohormones act as signal molecules that enhance cell death in response to ozone exposure. However, some studies have shown that ethylene and salicylic acid can instead decrease the magnitude of ozone-induced cell death. Therefore, we studied the defensive roles of ethylene and salicylic acid against ozone. Unlike the wild-type, Col-0, Arabidopsis mutants deficient in ethylene signaling (ein2) or salicylic acid biosynthesis (sid2) generated high levels of superoxide and exhibited visible leaf injury, indicating that ethylene and salicylic acid can reduce ozone damage. Macroarray analysis suggested that the ethylene and salicylic acid defects influenced glutathione (GSH) metabolism. Increases in the reduced form of GSH occurred in Col-0 6 h after ozone exposure, but little GSH was detected in ein2 and sid2 mutants, suggesting that GSH levels were affected by ethylene or salicylic acid signaling. We performed gene expression analysis by real-time polymerase chain reaction using genes involved in GSH metabolism. Induction of gamma-glutamylcysteine synthetase (GSH1), glutathione synthetase (GSH2), and glutathione reductase 1 (GR1) expression occurred normally in Col-0, but at much lower levels in ein2 and sid2. Enzymatic activities of GSH1 and GSH2 in ein2 and sid2 were significantly lower than in Col-0. Moreover, ozone-induced leaf damage observed in ein2 and sid2 was mitigated by artificial elevation of GSH content. Our results suggest that ethylene and salicylic acid protect against ozone-induced leaf injury by increasing de novo biosynthesis of GSH.

Salicylic acid-induced glutathione status in tomato crop and resistance to root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood

“…3,38 Integration of SA and JA signaling has been demonstrated 39 and SA reported to increase de novo biosynthesis of GSH. 40 In our studies, the ratio of GSH/GSSG was observed to be more in leaf and fruit than root tissues. In parallel with our observations, imbalances in GHS/GSSG ratio were reported when plants were exposed to oxidative stress.…”

Glutamate Receptor-Like Channel3.3 Is Involved in Mediating Glutathione-Triggered Cytosolic Calcium Transients, Transcriptional Changes, and Innate Immunity Responses in Arabidopsis

“…Particularly interesting is the finding that GSH induced expression of ICS1 and SARD1 in an AtGLR3.3-dependent manner, two essential genes for SA biosynthesis (Wildermuth et al, 2001;Zhang et al, 2010). A regulatory role for SA in GSH production in plants has been described (Srivastava and Dwivedi, 1998;Yoshida et al, 2009). Our finding that GSH can strongly induce ICS1 expression (Table I) implies that there is a positive AtGLR3.3-dependent feedback mechanism for GSH to enhance SA biosynthesis under stress conditions.…”

Cross-talk between sulfur assimilation and ethylene signaling in plants

“…However, additional evidence suggests that in addition to recycling the Met moieties via the Yang cycle, the de novo synthesis of Met is required when high rates of ethylene production are induced. 79 Moreover, S availability and ethylene have been shown to regulate GSH synthesis and stress tolerance to ozone 80 and Cd 81,82 stress. Glutathione acts as a storage and transport form for Cys; otherwise the excess Cys present in the cell becomes toxic.…”