Alternative photosynthetic electron flow to oxygen in marine Synechococcus

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• 作者：Shaun Bailey ; Anastasios Melis ; Katherine R.M. Mackey ; Pierre Cardol ; Giovanni Finazzi ; Gert van Dijken ; Gry Mine Berg ; Kevin Arrigo ; Jeff Shrager ; Arthur Grossman
• 关键词：Cyanobacteria ; Photosystem ; Oxidase ; Iron ; Oxygen ; Electron transport ; Alternative electron transport ; Synechococcus WH80102
• 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
• 出版年：2008
• 出版时间：March 2008
• 年：2008
• 卷：1777
• 期：3
• 页码：269-276
• 全文大小：544 K

文摘

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 b₆f 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 O₂, 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.