PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

Contribution of ATP synthesis to the repair of Photosystem II in the photodamage-repair cycle in Synechocystis. Suleyman Allakhverdiev^{*,1, 2}, Yoshitaka Nishiyama^{1, 3}, Shunichi Takahashi¹, Sachio Miyairi^{1, 4}, Iwane Suzuki¹, Norio Murata¹, ¹ National Institute for Basic Biology, Okazaki 444-8585, Japan² Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia³ Ehime University, Matsuyama 790-8577, Japan⁴ National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8566, Japan

ABSTRACT- The photosynthetic machinery, in particular, the photosystem II complex (PSII) is susceptible to strong light, and this phenomenon is called photodamage or photoinhibition. In living organisms, the photodamaged PSII is rapidly repaired and, as a result, the extent of photodamage is a result of balance between the photodamage and the repair of PSII. In this study, we examined the effects of electron transport and ATP synthesis on these two processes by measuring them separately and systematically in the cyanobacterium Synechocystis sp. PCC 6803. We found that the rate of photodamage which was proportional to light intensity was unaffected by inhibition of the electron transport in PSII, by acceleration of electron transport in PSI, or by inhibition of ATP synthesis. By contrast, the rate of repair was decreased by the inhibition of ATP synthesis either via PSI or PSII. Northern blotting and [³⁵S]methionine labeling analyses revealed that the synthesis of the D1 protein was enhanced by ATP synthesis. These observations suggest that ATP synthesis, but not the electron transport, regulates the repair of PSII, in particular, at the translation of the psbA genes, whereas neither of them affects the photodamage.

KEY WORDS: Photodamage, Repair, Photosystem II, D1 protein