Jasmonic Acid Signaling Modulates Ozone-Induced Hypersensitive Cell Death

Recent studies suggest that cross-talk between salicylic acid (SA)‐, jasmonic acid (JA)‐, and ethylene-dependent signaling pathways regulates plant responses to both abiotic and biotic stress factors. Earlier studies demonstrated that ozone (O 3 ) exposure activates a hypersensitive response (HR)‐like cell death pathway in the Arabidopsis ecotype Cvi-0. We now have confirmed the role of SA and JA signaling in influencing O 3 -induced cell death. Expression of salicylate hydroxylase (NahG) in Cvi-0 reduced O 3 -induced cell death. Methyl jasmonate (Me-JA) pretreatment of Cvi-0 decreased O 3 -induced H 2 O 2 content and SA concentrations and completely abolished O 3 -induced cell death. Cvi-0 synthesized as much JA as did Col-0 in response to O 3 exposure but exhibited much less sensitivity to exogenous Me-JA. Analyses of the responses to O 3 of the JA-signaling mutants jar1 and fad3/7/8 also demonstrated an antagonistic relationship between JA- and SA-signaling pathways in controlling the magnitude of O 3 -induced HR-like cell death.