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.
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.
Khatoon
Mahbuba
M
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
Inagawa
Kayo
K
Pospísil
Pavel
P
Yamashita
Amu
A
Yoshioka
Miho
M
Lundin
Björn
B
Horie
Junko
J
Morita
Noriko
N
Jajoo
Anjana
A
Yamamoto
Yoko
Y
Yamamoto
Yasusi
Y
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
D002412:Cations; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species