Abstract
Singlet oxygen, generated by photodynamic actions, is a strong oxidant that potentially damages various molecules of biological importance. We investigated the action in vivo of singlet oxygen in the photodamage to photosystem II (PSII) in the cyanobacterium Synechocystis sp. PCC 6803. Increases in intracellular concentrations of singlet oxygen by the presence of rose bengal resulted in inhibition of the repair of the photodamaged PSII and not in acceleration of direct damage to PSII. Labeling of proteins in vivo revealed that singlet oxygen inhibited the synthesis of proteins de novo and, in particular, that of the D1 protein. Northern blot analysis indicated that the accumulation of psbA mRNAs for the D1 protein was unaffected by the production of singlet oxygen, suggesting that the primary target of singlet oxygen might be translation.
