title: Photodamage to the oxygen evolving complex of photosystem II by visible light.
abstract: Light damages photosynthetic machinery, primarily photosystem II (PSII), and it results in photoinhibition. A new photodamage model, the two-step photodamage model, suggests that photodamage to PSII initially occurs at the oxygen evolving complex (OEC) by light energy absorbed by manganese and that the PSII reaction center is subsequently damaged by light energy absorbed by photosynthetic pigments due to the limitation of electrons to the PSII reaction center. However, it is still uncertain whether this model is applicable to photodamage to PSII under visible light as manganese absorbs visible light only weakly. In the present study, we identified the initial site of photodamage to PSII upon illumination of visible light using PSII membrane fragments isolated from spinach leaves. When PSII samples were exposed to visible light in the presence of an exogenous electron acceptor, both PSII total activity and the PSII reaction centre activity declined due to photodamage. The supplemental addition of an electron donor to the PSII reaction centre alleviated the decline of the reaction centre activity but not the PSII total activity upon the light exposure. Our results demonstrate that visible light damages OEC prior to photodamage to the PSII reaction center, consistent with two-step photodamage model.
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
authors.forename: Alonso
authors.initials: A
authors.lastname: Zavafer
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
authors.forename: Mun Hon
authors.initials: MH
authors.lastname: Cheah
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
authors.forename: Warwick
authors.initials: W
authors.lastname: Hillier
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
authors.affiliation: Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D004583:Electrons; D008027:Light; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D018724:Spinacia oleracea / Q000378:metabolism / Q000528:radiation effects
chemical_list: D045332:Photosystem II Protein Complex; D010100:Oxygen