Abstract
Chloramphenicol (CAP) is an inhibitor of protein synthesis, which is frequently used to decouple photodamage and protein synthesis dependent repair of Photosystem II during the process of photoinhibition. It has been reported earlier that CAP is able to mediate superoxide production by transferring electrons from the acceptor side of Photosystem I to oxygen. Here we investigated the interaction of CAP with Photosystem II electron transport processes by oxygen uptake and variable chlorophyll fluorescence measurements. Our data show that CAP can accept electrons at the acceptor side of Photosystem II, most likely from Pheophytin, and deliver them to molecular oxygen leading to superoxide production. In addition, the presence of CAP enhances photodamage of Photosystem II electron transport in isolated membrane particles, which effect is reversible by superoxide dismutase. It is concluded that CAP acts as electron acceptor in Photosystem II and mediates its superoxide dependent photodamage. This effect has potential implications for the application of CAP in photoinhibitory studies in intact systems.
Highlights
Photosynthesis is a process in which green plants, algae and cyanobacteria utilize energy from sunlight to manufacture carbohydrates from carbon dioxide and water
Since we have shown that CAP functions as PSI electron acceptor, but takes up electrons from Photosystem II (PSII) it has a potential to produce superoxide in PSII complexes as, well
Our data show that CAP accepts electrons from the PSII complex at a site located before the QB quinone electron acceptor, most likely from Phe−
Summary
Photosynthesis is a process in which green plants, algae and cyanobacteria utilize energy from sunlight to manufacture carbohydrates from carbon dioxide and water. Too much light reaching the photosynthetic apparatus can cause photodamage and can lead to the death of a cell This stress situation is known as photoinhibition (Arntzen et al, 1984; Aro et al, 1993; Vass and Aro, 2008). Superoxide radicals have high reactivity, it is expected that locally generated superoxide will induce damaging effects in the vicinity of its production This finding has been considered as a source of potential artifact by several research groups, who used lincomycin instead of CAP in photoinhibition studies (Tyystjarvi and Aro, 1996; Constant et al, 1997; Tyystjarvi et al, 2002; Chow et al, 2005; Campbell and Tyystjärvi, 2012; Miyata et al, 2012; Tikkanen et al, 2014). Fv/Fm was obtained by calculating (Fm-Fo)/Fm, where Fo and Fm represent the minimum fluorescence in dark adapted sample, and the maximal fluorescence yield under continuous saturating light, respectively
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