[转移贴]Nature：噬蓝藻体中也存在光合体系-I

cao1976

原贴由wwwkkk83发表于 2009-9-23 16:36

植物叶绿体一样，海洋蓝细菌的光合作用膜也含有两个光合体系：光合体系-II（PSII）调控电子从水到质体醌（亦称叶绿醌）的转移，而光合体系-I（PSI）调控电子从质体蓝素向铁氧化还原蛋白的转移，从而减少以NADPH（还原型辅酶Ⅱ）形式固定CO2所需能量。

核心PSII基因最近在噬蓝藻体（感染蓝细菌的病毒）中被发现，在那里它们的作用可能是补充宿主的光合作用能力。现在，对来自“Sorcerer II全球海洋取样考察”项目的元基因组数据和有关病毒生物区系的研究数据所做的一项分析表明，PSI成分也存在于噬蓝藻体中，也可能具有帮助提高光合作用整体表现的功能。
原始出处：Nature 461, 258-262 (10 September 2009) | doi:10.1038/nature08284

Photosystem I gene cassettes are present in marine virus genomes

Itai Sharon1,2,9, Ariella Alperovitch1,9, Forest Rohwer4,5, Matthew Haynes4, Fabian Glaser3, Nof Atamna-Ismaeel1, Ron Y. Pinter2, Frédéric Partensky6, Eugene V. Koonin7, Yuri I. Wolf7, Nathan Nelson8 & Oded Béjà1

Cyanobacteria of the Synechococcus and Prochlorococcus genera are important contributors to photosynthetic productivity in the open oceans1, 2, 3. Recently, core photosystem II (PSII) genes were identified in cyanophages and proposed to function in photosynthesis and in increasing viral fitness by supplementing the host production of these proteins4, 5, 6, 7. Here we show evidence for the presence of photosystem I (PSI) genes in the genomes of viruses that infect these marine cyanobacteria, using pre-existing metagenomic data from the global ocean sampling expedition8 as well as from viral biomes9. The seven cyanobacterial core PSI genes identified in this study, psaA, B, C, D, E, K and a unique J and F fusion, form a cluster in cyanophage genomes, suggestive of selection for a distinct function in the virus life cycle. The existence of this PSI cluster was confirmed with overlapping and long polymerase chain reaction on environmental DNA from the Northern Line Islands. Potentially, the seven proteins encoded by the viral genes are sufficient to form an intact monomeric PSI complex. Projection of viral predicted peptides on the cyanobacterial PSI crystal structure10 suggested that the viral–PSI components might provide a unique way of funnelling reducing power from respiratory and other electron transfer chains to the PSI.