title: Enzymatic, but not non-enzymatic, 1O2-mediated peroxidation of polyunsaturated fatty acids forms part of the EXECUTER1-dependent stress response program in the flu mutant of Arabidopsis thaliana.
abstract: The conditional flu mutant of Arabidopsis accumulates excess amounts of protochlorophyllide within plastid membranes in the dark and generates singlet oxygen upon light exposure. By varying the length of the dark period, the level of the photosensitizer protochlorophyllide may be modulated, and conditions have been established that either endorse the cytotoxicity of (1)O(2) or reveal its signaling role. Two criteria have been used to distinguish between these two modes of activity of (1)O(2): the impact of the EXECUTER1 mutation and the prevalence of either non-enzymatic or enzymatic lipid peroxidation. During illumination of etiolated flu seedlings, toxic effects of (1)O(2) prevail and non-enzymatic lipid peroxidation proceeds rapidly. In contrast, in light-grown flu plants that were subjected to an 8 h dark/light shift, lipid peroxidation occurred almost exclusively enzymatically. The resulting oxidation product, 13-hydroperoxy octadecatrienoic acid (13-HPOT), serves as a substrate for synthesis of 12-oxo phytodienoic acid (OPDA) and jasmonic acid (JA), both of which are known to control various metabolic and developmental processes in plants. Inactivation of the EXECUTER1 protein abrogates not only (1)O(2)-mediated cell death and growth inhibition of flu plants, but also enzymatic lipid peroxidation. However, inactivation of jasmonate biosynthesis in the aos/flu double mutant does not affect (1)O(2)-mediated growth inhibition and cell death. Hence, JA and OPDA do not act as second messengers during (1)O(2) signaling, but form an integral part of a stress-related signaling cascade activated by (1)O(2) that encompasses several signaling pathways known to be activated by abiotic and biotic stressors.
authors.affiliation: Swiss Federal Institute of Technology (ETH), Institute of Plant Sciences, Universitätsstrasse 2, CH-8092 Zürich, Switzerland.
authors.forename: Dominika
authors.initials: D
authors.lastname: Przybyla
authors.forename: Cornelia
authors.initials: C
authors.lastname: Göbel
authors.forename: André
authors.initials: A
authors.lastname: Imboden
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.forename: Klaus
authors.initials: K
authors.lastname: Apel
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D016923:Cell Death; D003517:Cyclopentanes / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D015227:Lipid Peroxidation; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D054883:Oxylipins / Q000378:metabolism; D026082:Singlet Oxygen; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; C521350:EXECUTER1 protein, Arabidopsis; C478633:FLU protein, Arabidopsis; D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D026082:Singlet Oxygen; C025999:12-oxophytodienoic acid; C011006:jasmonic acid