Alternative photosynthetic electron flow to oxygen in marine Synechococcus
Alternative photosynthetic electron flow to oxygen in marine Synechococcus
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DOI：
10.1016/j.bbabio.2008.01.002
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发表时间：
2008-03-01
影响因子：
4.3
通讯作者：
Grossman, Arthur
中科院分区：
文献类型：
--
作者：
Bailey, Shaun;Melis, Anastasios;Grossman, Arthur
蓝藻主宰着世界上的海洋，那里的铁通常几乎检测不到。贫营养海洋环境中低铁适应的一个表现是富铁光合组分水平的降低，包括光系统I的反应中心和细胞色素B（6）f复合物[R. F. Strzepek和P.J. Harrison，Photosynthetic architecture differs in coastal and oceanic diatoms，Nature 431（2004）689-692.]。这些类囊体膜组分在线性和循环光合电子传递中具有良好的特征作用，它们的低丰度对光合功能产生了潜在的障碍。在这里，我们表明，海洋蓝藻聚球藻WH 8102表现出显着的替代电子流O-2，一个潜在的适应贫营养海洋的低铁环境。这种交替的电子流似乎在光系统I之前从系统间电子传递链中提取电子。抑制剂的研究表明，没食子酸丙酯敏感的氧化酶介导这种电子流到氧气，这反过来又会导致过度的光系统II激发压力，即使在相对较低的辐照度下也经常发生。这些研究结果也讨论了在满足细胞的能量需求时，光系统I丰度低的背景下。(C)2008 Elsevier B. V.保留所有权利。
Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b(6)f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O-2, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low. (C) 2008 Elsevier B.V. All rights reserved.