Jasmonic acid signaling modulates ozone-induced hypersensitive cell death

Recent studies suggest that cross-talk between salicylic acid (SA)-, jasmon ic acid (JA)-, and ethylene-dependent signaling pathways regulates plant re sponses to both abiotic and biotic stress factors. Earlier studies demonstr ated that ozone (O-3) exposure activates a hypersensitive response (HR)-lik e cell death pathway in the Arabidopsis ecotype Cvi-0. We now have confirme d the role of SA and JA signaling in influencing O-3-induced cell death. Ex pression of salicylate hydroxylase (NahG) in Cvi-0 reduced O-3-induced cell death. Methyl jasmonate (Me-JA) pretreatment of Cvi-O decreased O-3-induce d H2O2 content and SA concentrations and completely abolished O-3-induced c ell death. Cvi-0 synthesized as much JA as did Col-0 in response to O-3 exp osure but exhibited much less sensitivity to exogenous Me-JA. Analyses of t he responses to O-3 Of the JA-signaling mutants jar1 and fad3/7/8 also demo nstrated an antagonistic relationship between JA- and SA-signaling pathways in controlling the magnitude of O-3-induced HR-like cell death.