title: Chemical quenching of singlet oxygen by carotenoids in plants.
abstract: Carotenoids are considered to be the first line of defense of plants against singlet oxygen ((1)O(2)) toxicity because of their capacity to quench (1)O(2) as well as triplet chlorophylls through a physical mechanism involving transfer of excitation energy followed by thermal deactivation. Here, we show that leaf carotenoids are also able to quench (1)O(2) by a chemical mechanism involving their oxidation. In vitro oxidation of β-carotene, lutein, and zeaxanthin by (1)O(2) generated various aldehydes and endoperoxides. A search for those molecules in Arabidopsis (Arabidopsis thaliana) leaves revealed the presence of (1)O(2)-specific endoperoxides in low-light-grown plants, indicating chronic oxidation of carotenoids by (1)O(2). β-Carotene endoperoxide, but not xanthophyll endoperoxide, rapidly accumulated during high-light stress, and this accumulation was correlated with the extent of photosystem (PS) II photoinhibition and the expression of various (1)O(2) marker genes. The selective accumulation of β-carotene endoperoxide points at the PSII reaction centers, rather than the PSII chlorophyll antennae, as a major site of (1)O(2) accumulation in plants under high-light stress. β-Carotene endoperoxide was found to have a relatively fast turnover, decaying in the dark with a half time of about 6 h. This carotenoid metabolite provides an early index of (1)O(2) production in leaves, the occurrence of which precedes the accumulation of fatty acid oxidation products.
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, Direction des Sciences du Vivant, Institut de Biologie Environnementale et de Biotechnologie, F-13108 Saint-Paul-lez-Durance, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Ramel
authors.forename: Simona
authors.initials: S
authors.lastname: Birtic
authors.forename: Stéphan
authors.initials: S
authors.lastname: Cuiné
authors.forename: Christian
authors.initials: C
authors.lastname: Triantaphylidès
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Ravanat
authors.forename: Michel
authors.initials: M
authors.lastname: Havaux
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics; D002338:Carotenoids / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006207:Half-Life; D008027:Light; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D055668:Photochemical Processes; D045332:Photosystem II Protein Complex / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D026082:Singlet Oxygen; D002338:Carotenoids