title: Zeaxanthin and Echinenone Protect the Repair of Photosystem II from Inhibition by Singlet Oxygen in Synechocystis sp. PCC 6803.
abstract: Carotenoids are important components of antioxidative systems in photosynthetic organisms. We investigated the roles of zeaxanthin and echinenone in the protection of PSII from photoinhibition in Synechocystis sp. PCC 6803, using mutants of the cyanobacterium that lack these carotenoids. The activity of PSII in mutant cells deficient in either zeaxanthin or echinenone was more sensitive to strong light than the activity in wild-type cells, and the activity in mutant cells deficient in both carotenoids was hypersensitive to strong light, indicating that the absence of these carotenoids increased the extent of photoinhibition. Nonetheless, the rate of photodamage to PSII, as measured in the presence of chloramphenicol, which blocks the repair of PSII, was unaffected by the absence of either carotenoid, suggesting that these carotenoids might act by protecting the repair of PSII. Knockout of the gene for the so-called orange carotenoid protein (OCP), in which the 3'-hydroxyechinenone cofactor, a derivative of echinenone, is responsible for the thermal dissipation of excitation energy, increased the extent of photoinhibition but did not affect photodamage, suggesting that thermal dissipation also protects the repair of PSII. In mutant cells lacking OCP, as well as those lacking zeaxanthin and echinenone, the production of singlet oxygen was stimulated and the synthesis de novo of various proteins, including the D1 protein, was markedly suppressed under strong light. These observations suggest that the carotenoids and thermal dissipation might protect the repair of photodamaged PSII by depressing the levels of singlet oxygen that inhibits protein synthesis.
authors: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan.
authors: Yuri
authors: Y
authors: Kusama
authors: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan.
authors: Shuhei
authors: S
authors: Inoue
authors: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan.
authors: Haruhiko
authors: H
authors: Jimbo
authors: Department of Biology, Nippon Medical School, Kyonan-cho, Musashino, Tokyo, 180-0023 Japan.
authors: Shinichi
authors: S
authors: Takaichi
authors: Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480 Japan.
authors: Kintake
authors: K
authors: Sonoike
authors: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan Institute for Environmental Science and Technology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan.
authors: Yukako
authors: Y
authors: Hihara
authors: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan Institute for Environmental Science and Technology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan nishiyama@molbiol.saitama-u.ac.jp.
authors: Yoshitaka
authors: Y
authors: Nishiyama
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000187:drug effects; D002338:Carotenoids / Q000096:biosynthesis / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D016680:Genome, Bacterial; D042541:Intracellular Space / Q000378:metabolism; D008027:Light; D009154:Mutation / Q000528:radiation effects; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D020011:Protective Agents / Q000494:pharmacology*; D026082:Singlet Oxygen / Q000633:toxicity*; D046939:Synechocystis / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D065146:Zeaxanthins / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; D020011:Protective Agents; D065146:Zeaxanthins; C109473:orange carotenoid protein, Synechocystis; D026082:Singlet Oxygen; D002338:Carotenoids; C105515:echinenone
keywords: Echinenone; Orange carotenoid protein; Photoinhibition; Photosystem II; Singlet oxygen; Zeaxanthin