title: Cu(2+) inhibits photosystem II activities but enhances photosystem I quantum yield of Microcystis aeruginosa.
abstract: Responses of photosystem I and II activities of Microcystis aeruginosa to various concentrations of Cu(2+) were simultaneously examined using a Dual-PAM-100 fluorometer. Cell growth and contents of chlorophyll a were significantly inhibited by Cu(2+). Photosystem II activity [Y(II)] and electron transport [rETRmax(II)] were significantly altered by Cu(2+). The quantum yield of photosystem II [Y(II)] decreased by 29 % at 100 μg L(-1) Cu(2+) compared to control. On the contrary, photosystem I was stable under Cu(2+) stress and showed an obvious increase of quantum yield [Y(I)] and electron transport [rETRmax(I)] due to activation of cyclic electron flow (CEF). Yield of cyclic electron flow [Y(CEF)] was enhanced by 17 % at 100 μg L(-1) Cu(2+) compared to control. The contribution of linear electron flow to photosystem I [Y(II)/Y(I)] decreased with increasing Cu(2+) concentration. Yield of cyclic electron flow [Y(CEF)] was negatively correlated with the maximal photosystem II photochemical efficiency (F v/F m). In summary, photosystem II was the major target sites of toxicity of Cu(2+), while photosystem I activity was enhanced under Cu(2+) stress.
authors.affiliation: Key Lab of Plateau Lake Ecology and Global Change, College of Tourism and Geographic Science, Yunnan Normal University, Kunming, 650500, China.
authors.forename: Chunnuan
authors.initials: C
authors.lastname: Deng
authors.forename: Xiangliang
authors.initials: X
authors.lastname: Pan
authors.forename: Shuzhi
authors.initials: S
authors.lastname: Wang
authors.forename: Daoyong
authors.initials: D
authors.lastname: Zhang
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D003300:Copper / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport / Q000187:drug effects; D046931:Microcystis / Q000187:drug effects* / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D003300:Copper