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A specific role for tocopherol and of chemical singlet oxygen quenchers in the maintenance of photosystem II structure and function in Chlamydomonas reinhardtii
Author(s) -
Trebst Achim,
Depka Brigitte,
Holländer-Czytko Heike
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02526-7
Subject(s) - singlet oxygen , chlamydomonas reinhardtii , photosystem ii , chemistry , photochemistry , photosynthesis , photosynthetic reaction centre , tocopherol , quenching (fluorescence) , oxygen , singlet state , biochemistry , vitamin e , excited state , organic chemistry , antioxidant , fluorescence , mutant , physics , quantum mechanics , nuclear physics , gene
α‐Tocopherol concentrations were determined at low and high light intensities and compared with the rate of photosynthesis, photosystem II (PS II) and its reaction center D1 protein. Blocking of tocopherol biosynthesis at the 4‐hydroxyphenylpyruvate dioxygenase by the herbicide pyrazolynate led to a quick disappearance of α‐tocopherol in high light, as well as of PS II activity and the D1 protein. Homogentisic acid rescued all activities. It is concluded that α‐tocopherol has a continuous turnover as a scavenger of the singlet oxygen that arises from the quenching by oxygen of the triplet of the PS II reaction center and triggers the degradation of the D1 protein. Thus tocopherols are essential to keep photosynthesis active. We suggest that this is why plants make and need tocopherols. Chemical quenchers of singlet oxygen, notably diphenylamines, completely protect PS II, prevent D1 protein degradation and keep tocopherol levels even at very high light intensities. This supports the notion that 1 O 2 is the intermediate in light triggered D1 protein turnover.