title: Quality control of photosystem II: Thylakoid unstacking is necessary to avoid further damage to the D1 protein and to facilitate D1 degradation under light stress in spinach thylakoids.
abstract: Photosystem II is vulnerable to light damage. The reaction center-binding D1 protein is impaired during excessive illumination and is degraded and removed from photosystem II. Using isolated spinach thylakoids, we investigated the relationship between light-induced unstacking of thylakoids and damage to the D1 protein. Under light stress, thylakoids were expected to become unstacked so that the photodamaged photosystem II complexes in the grana and the proteases could move on the thylakoids for repair. Excessive light induced irreversible unstacking of thylakoids. By comparing the effects of light stress on stacked and unstacked thylakoids, photoinhibition of photosystem II was found to be more prominent in stacked thylakoids than in unstacked thylakoids. In accordance with this finding, EPR spin trapping measurements demonstrated higher production of hydroxyl radicals in stacked thylakoids than in unstacked thylakoids. We propose that unstacking of thylakoids has a crucial role in avoiding further damage to the D1 protein and facilitating degradation of the photodamaged D1 protein under light stress.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
authors.forename: Mahbuba
authors.initials: M
authors.lastname: Khatoon
authors.forename: Kayo
authors.initials: K
authors.lastname: Inagawa
authors.forename: Pavel
authors.initials: P
authors.lastname: Pospísil
authors.forename: Amu
authors.initials: A
authors.lastname: Yamashita
authors.forename: Miho
authors.initials: M
authors.lastname: Yoshioka
authors.forename: Björn
authors.initials: B
authors.lastname: Lundin
authors.forename: Junko
authors.initials: J
authors.lastname: Horie
authors.forename: Noriko
authors.initials: N
authors.lastname: Morita
authors.forename: Anjana
authors.initials: A
authors.lastname: Jajoo
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yasusi
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D002412:Cations; D002736:Chloroplasts / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D004591:Electrophoresis, Polyacrylamide Gel; D008027:Light; D008954:Models, Biological; D010777:Photochemistry / Q000379:methods; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species; D013053:Spectrophotometry / Q000379:methods; D018724:Spinacia oleracea / Q000201:enzymology / Q000502:physiology; D020524:Thylakoids / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002412:Cations; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species