Extracellular production and degradation of superoxide in the coral Stylophora pistillata and cultured Symbiodinium.
Extracellular production and degradation of superoxide in the coral Stylophora pistillata and cultured Symbiodinium.
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DOI：
10.1371/journal.pone.0012508
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发表时间：
2010-09-14
期刊：
影响因子：
3.7
通讯作者：
Shaked Y
中科院分区：
文献类型：
--
作者：
Saragosti E;Tchernov D;Katsir A;Shaked Y
活性氧（ROS）被认为是在细胞死亡途径和漂白的石珊瑚中发挥重要作用。珊瑚中活性氧的直接测量明显供不应求，部分原因是细胞系统中活性氧定量的固有问题。在这项研究中，我们的特点是动态的活性氧物种超氧阴离子自由基（O2 −）的珊瑚Stylophora pistillata的外部环境。使用一个敏感的，快速的和选择性的荧光为基础的技术，我们测量了细胞外超氧化物的生产和解毒活性的共生体（非漂白）和aposymbiont（漂白）珊瑚，和培养的共生藻（从分支A和C）。漂白和未漂白的柱花草碎片在黑暗中产生超氧化物的速率相当，为10−11-10−9 mol O2 − mg protein−1 min−1。在光照下，在未漂白的珊瑚中观察到O2 −产生速率的两倍增强，但在漂白的珊瑚中没有。培养的共生藻在黑暗中产生超氧化物的速率为。研究发现，光照可以显著提高O2 −的产生。NADPH氧化酶抑制剂氯化二苯基碘铵（DPI）强烈抑制珊瑚（和藻类）的O2 −产生，可能表明NADPH氧化酶参与了这一过程。发现漂白和未漂白的Stylophora具有细胞外O2 −解毒活性，但Symbiodinium没有。O2 −解毒活性被部分表征，并发现类似于超氧化物歧化酶（SOD）。大量的细胞外O2 −产生以及细胞外O2 −解毒活性的发现可能揭示共生体与其宿主之间以及珊瑚与其环境之间的化学相互作用。共生藻产生的超氧化物可能意味着含藻珊瑚更容易受到内部O2 −积累的影响，这可能反过来与氧化应激介导的漂白有关。
Reactive oxygen species (ROS) are thought to play a major role in cell death pathways and bleaching in scleractinian corals. Direct measurements of ROS in corals are conspicuously in short supply, partly due to inherent problems with ROS quantification in cellular systems. In this study we characterized the dynamics of the reactive oxygen species superoxide anion radical (O2 −) in the external milieu of the coral Stylophora pistillata. Using a sensitive, rapid and selective chemiluminesence-based technique, we measured extracellular superoxide production and detoxification activity of symbiont (non-bleached) and aposymbiont (bleached) corals, and of cultured Symbiodinium (from clades A and C). Bleached and non-bleached Stylophora fragments were found to produce superoxide at comparable rates of 10−11–10−9 mol O2 − mg protein−1 min−1 in the dark. In the light, a two-fold enhancement in O2 − production rates was observed in non-bleached corals, but not in bleached corals. Cultured Symbiodinium produced superoxide in the dark at a rate of . Light was found to markedly enhance O2 − production. The NADPH Oxidase inhibitor Diphenyleneiodonium chloride (DPI) strongly inhibited O2 − production by corals (and more moderately by algae), possibly suggesting an involvement of NADPH Oxidase in the process. An extracellular O2 − detoxifying activity was found for bleached and non-bleached Stylophora but not for Symbiodinium. The O2 − detoxifying activity was partially characterized and found to resemble that of the enzyme superoxide dismutase (SOD). The findings of substantial extracellular O2 − production as well as extracellular O2 − detoxifying activity may shed light on the chemical interactions between the symbiont and its host and between the coral and its environment. Superoxide production by Symbiodinium possibly implies that algal bearing corals are more susceptible to an internal build-up of O2 −, which may in turn be linked to oxidative stress mediated bleaching.
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