title: Elucidating the toxicity targets of β-ionone on photosynthetic system of Microcystis aeruginosa NIES-843 (Cyanobacteria).
abstract: In order to explore the potential targets of toxicity of β-ionone on the photosynthetic system of Microcystis aeruginosa, the polyphasic rise in chlorophyll a (Chl a) fluorescence transient and transcript expression for key genes in photosystem II (PSII) of M. aeruginosa NIES-843 were studied. The EC₅₀ value of β-ionone on M. aeruginosa NIES-843 was found to be 21.23±1.87 mg/L. It was shown that β-Ionone stress can lead to a decrease in pigment content of M. aeruginosa NIES-843 cells, and that carotenoids were more sensitive to β-ionone stress than Chl a. The normalized Chl a fluorescence transients were slightly decreased at 6.67 and 10 mg/L β-ionone, but significantly increased at 15, 22.5 and 33.75 mg/L. There was no significant variation on transcript expression of psbA and psbO at a concentration of 6.67 mg/L β-ionone, but they were down-regulated at 22.5 mg/L. Ultrastructural examination by transmission electron microscopy indicated that the thylakoids were distorted, and the thylakoid membrane stacks began to collapse when M. aeruginosa NIES-843 was exposed to β-ionone at a concentration of 22.5 and 33.75 mg/L. Our results indicate that the reaction centre of PS II and the electron transport at the acceptor side of PS II are the targets responsible for the toxicity of β-ionone on the PS II of M. aeruginosa NIES-843.
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Jihai
authors.initials: J
authors.lastname: Shao
authors.forename: Yao
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhongjie
authors.initials: Z
authors.lastname: Wang
authors.forename: Yongguang
authors.initials: Y
authors.lastname: Jiang
authors.forename: Gongliang
authors.initials: G
authors.lastname: Yu
authors.forename: Xin
authors.initials: X
authors.lastname: Peng
authors.forename: Renhui
authors.initials: R
authors.lastname: Li
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D015870:Gene Expression / Q000187:drug effects; D046931:Microcystis / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D045792:Norisoprenoids / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects* / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D045792:Norisoprenoids; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; C008157:beta-ionone; D000077194:Chlorophyll A