Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
Aquat Toxicol. 2011 Jul;104(1-2):48-55. doi: 10.1016/j.aquatox.2011.03.014. Epub 2011 Mar 30.
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.
为了探究β-紫罗兰酮对铜绿微囊藻光合作用系统毒性的潜在靶标，研究了铜绿微囊藻 NIES-843 中光系统 II（PSII）关键基因的叶绿素 a（Chl a）荧光动力学和转录表达的多相上升。发现β-紫罗兰酮对铜绿微囊藻 NIES-843 的 EC₅₀值为 21.23±1.87mg/L。结果表明，β-紫罗兰酮胁迫会导致铜绿微囊藻 NIES-843 细胞色素含量降低，类胡萝卜素比 Chl a 对β-紫罗兰酮胁迫更敏感。在 6.67 和 10mg/Lβ-紫罗兰酮下，归一化 Chl a 荧光动力学略有下降，但在 15、22.5 和 33.75mg/L 下显著增加。在 6.67mg/Lβ-紫罗兰酮浓度下，psbA 和 psbO 的转录表达没有显著变化，但在 22.5mg/L 时下调。透射电子显微镜的超微结构检查表明，当铜绿微囊藻暴露于 22.5 和 33.75mg/Lβ-紫罗兰酮时，类囊体扭曲，类囊体膜堆叠开始崩溃。我们的结果表明，PS II 的反应中心和 PS II 的受体侧电子传递是β-紫罗兰酮对铜绿微囊藻 PS II 毒性的靶标。
