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First published online October 21, 2005; 10.1104/pp.105.068643 Plant Physiology 139:1175-1184 (2005) © 2005 American Society of Plant Biologists
PsbP Protein, But Not PsbQ Protein, Is Essential for the Regulation and Stabilization of Photosystem II in Higher Plants1Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606–8502, Japan (K.I., Y.Y., S.I., F.S.); and Laboratory for Photo-Biology (1), RIKEN Photodynamics Research Center, Aoba-ku, Sendai 980–0845, Japan (T.O.)
PsbP and PsbQ proteins are extrinsic subunits of photosystem II (PSII) and participate in the normal function of photosynthetic water oxidation. Both proteins exist in a broad range of the oxygenic photosynthetic organisms; however, their physiological roles in vivo have not been well defined in higher plants. In this study, we established and analyzed transgenic tobacco (Nicotiana tabacum) plants in which the levels of PsbP or PsbQ were severely down-regulated by the RNA interference technique. A plant that lacked PsbQ showed no specific phenotype compared to a wild-type plant. This suggests that PsbQ in higher plants is dispensable under the normal growth condition. On the other hand, a plant that lacked PsbP showed prominent phenotypes: drastic retardation of growth, pale-green-colored leaves, and a marked decrease in the quantum yield of PSII evaluated by chlorophyll fluorescence. In PsbP-deficient plant, most PSII core subunits were accumulated in thylakoids, whereas PsbQ, which requires PsbP to bind PSII in vitro, was dramatically decreased. PSII without PsbP was hypersensitive to light and rapidly inactivated when the repair process of the damaged PSII was inhibited by chloramphenicol. Furthermore, thermoluminescence studies showed that the catalytic manganese cluster in PsbP-deficient leaves was markedly unstable and readily disassembled in the dark. The present results demonstrated that PsbP, but not PsbQ, is indispensable for the normal PSII function in higher plants in vivo.
1 This work was supported in part by a Research for the Future Program Grant from the Japan Society for the Promotion of Science (JSPS-RFTF 00L01606 to F.S.), by a grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (grant no. 15770026 to K.I.), and a Research Grant from Nissan Science Foundation (to K.I.). 2 These authors contributed equally to the paper. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Fumihiko Sato (fumihiko{at}kais.kyoto-u.ac.jp). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.068643. * Corresponding author; e-mail fumihiko{at}kais.kyoto-u.ac.jp; fax 81–75–753–6398. Received July 21, 2005; returned for revision September 17, 2005; accepted September 19, 2005. This article has been cited by other articles:
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