title: Quality control of photosystem II: direct imaging of the changes in the thylakoid structure and distribution of FtsH proteases in spinach chloroplasts under light stress.
abstract: Under light stress, the reaction center-binding protein D1 of PSII is photo-oxidatively damaged and removed from PSII complexes by proteases located in the chloroplast. A protease considered to be responsible for degradation of the damaged D1 protein is the metalloprotease FtsH. We showed previously that the active hexameric FtsH protease is abundant at the grana margin and the grana end membranes, and this homo-complex removes the photodamaged D1 protein in the grana. Here, we showed a change in the distribution of FtsH in spinach thylakoids during excessive illumination by transmission electron microscopy (TEM) and immunogold labeling of FtsH. The change in distribution of the protease was accompanied by structural changes to the thylakoids, which we detected using spinach leaves by TEM after chemical fixation of the samples. Quantitative analyses showed several characteristic changes in the structure of the thylakoids, including shrinkage of the grana, outward bending of the marginal portions of the thylakoids and an increase in the height of the grana stacks under excessive illumination. The increase in the height of the grana stacks may include swelling of the thylakoids and an increase in the partition gaps between the thylakoids. These data strongly suggest that excessive illumination induces partial unstacking of the thylakoids, which enables FtsH to access easily the photodamaged D1 protein. Finally three-dimensional tomography of the grana was recorded to observe the effect of light stress on the overall structure of the thylakoids.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 JapanThese authors contributed equally to this work. yoshi-m3@cc.okayama-u.ac.jp.
authors.forename: Miho
authors.initials: M
authors.lastname: Yoshioka-Nishimura
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 JapanThese authors contributed equally to this work.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nanba
authors.affiliation: Techinical support center, JEOL, Akishima, 196-0022 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Takaki
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Ohba
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan.
authors.forename: Nodoka
authors.initials: N
authors.lastname: Tsumura
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Morita
authors.affiliation: Ushimado Marine Institute, Okayama University, Setouchi, 701-4303 Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sakamoto
authors.affiliation: National Institute for Physiological Sciences, Okazaki, 444-8585 Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Murata
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan.
authors.forename: Yasusi
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D001692:Biological Transport; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D021621:Imaging, Three-Dimensional; D008027:Light; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D010447:Peptide Hydrolases / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism; D018724:Spinacia oleracea / Q000378:metabolism / Q000648:ultrastructure*; D013312:Stress, Physiological; D020524:Thylakoids / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D010447:Peptide Hydrolases
keywords: FtsH protease; Light stress; Photosystem II; Spinach chloroplast; TEM; Thylakoid