Production of reactive oxygen species in chloride- and calcium-depleted photosystem II and their involvement in photoinhibition

Abstract

Mixed photosystem II (PSII) samples consisting of Cl(-)-depleted and active, or Ca(2+)-depleted and active PSII enriched membrane fragments, respectively, were investigated with respect to their susceptibility to light. In the presence of Cl(-)-depleted PSII, active centers were damaged more severely, most likely caused by a higher amount of reactive oxygen species formed in the nonfunctional centers. Cl(-) depletion led to an increased H(2)O(2) production, which seemed to be responsible for the stimulation of PSII activity loss. To distinguish between direct H(2)O(2) formation by partial water oxidation and indirect H(2)O(2) formation by oxygen reduction involving the prior formation of O(2)(-?), the production of reactive oxygen species was followed by spin trapping EPR spectroscopy. All samples investigated, i.e. PSII with a functional water splitting complex, Ca(2+)- and Cl(-)-depleted PSII, produced upon illumination O(2)(-?) and OH(?) radicals on the acceptor side, while Cl(-)-depleted PSII produced additionally OH(?) radicals originating from H(2)O(2) formed on the donor side of PSII.

Amino acid oxidation of the D1 and D2 proteins by oxygen radicals during photoinhibition of Photosystem II

“…S1B). This observation is in agreement with previous reports that chloride-depleted PSII membranes produced more HO • compared with control PSII membranes (33,34). The involvement of chloride in HO • formation is supported by the observation that acetate and DIDS nearly abolished detectable HO • production (Fig.…”

PsbP Protein, But Not PsbQ Protein, Is Essential for the Regulation and Stabilization of Photosystem II in Higher Plants

“…Reductants such as ascorbate or ferrocyanide do not release Mn from PSII depleted of PsbP and PsbQ (Ghanotakis et al, 1984b). Previous studies suggested that H 2 O 2 is generated from the PSII acceptor side when the oxidation of Q A 2 is perturbed (Schrö der and Å kerlund, 1990), or from the PSII donor side when the function of the Mn cluster is impaired (Schrö der and Å kerlund, 1986;Fine and Frasch, 1992;Hillier and Wydrzynski, 1993;Klimov et al, 1993;Arató et al, 2004). PSII depleted of the Mn cluster has also been reported to generate O 2 2 efficiently (Chen et al, 1995).…”

Oxygen Metabolism in Chloroplast

“…At the acceptor side, H 2 O 2 can be formed outside thylakoids by the dismutation of O 2 •− produced within membrane (Arato et al, 2004;Klimov et al, 1993) or inside the membrane by the interaction of O 2 •− with non-heme iron of PSII (Pospíšil et al, 2004). At the donor side H 2 O 2 can be formed as an intermediate during water oxidizing cycle operation if this cycle is seriously disrupted (Ananyev et al, 1992;Hillier & Wydrzynski, 1993).…”

“…The various treatments of isolated PSII particles can lead to hydroxyl radical generation (Arato et al, 2004;Pospíšil et al, 2004). Production of hydroxyl radical by PSII is limited under normal functional conditions unlike under the strong stress conditions.…”