Overexpression of plastid terminal oxidase in Synechocystis sp PCC 6803 alters cellular redox state
Overexpression of plastid terminal oxidase in Synechocystis sp PCC 6803 alters cellular redox state
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DOI：
10.1098/rstb.2016.0379
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发表时间：
2017-09-26
影响因子：
6.3
通讯作者：
Krieger-Liszkay, Anja
中科院分区：
文献类型：
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作者：
Feilke, Kathleen;Ajlani, Ghada;Krieger-Liszkay, Anja
蓝藻是最古老的进行光合作用的生物，是植物质体的祖先。所有质体都含有质体末端氧化酶（PTOX），而只有某些蓝藻含有PTOX。PTOX在高等植物中的许多假定功能已经被讨论，包括在非生物胁迫如强光、盐度和极端温度下的光保护作用。由于PTOX氧化PQH（2）并将氧气还原为水，因此认为其通过从质体醌（PQ）池中去除过量电子来防止光氧化损伤。为了研究PTOX的作用，我们过表达水稻PTOX融合麦芽糖结合蛋白（MBP-OsPTOX）在集胞藻属PCC 6803，模式蓝藻，不编码PTOX。通过叶绿素荧光和P-700吸收测量，融合蛋白被高度表达并且OsPTOX是活性的。PTOX的存在导致NAD（P）H/NAD（P）（+）池的高度氧化状态，如通过NAD（P）H荧光检测的。此外，在PTOX过表达的PSI相对于PSII的电子传递能力较高，表明光系统I（PSI）的光系统II（PSII）的化学计量的改变。我们认为PTOX以不同于PQ/PQH（2）比率的方式控制光合机构的响应基因的表达。本文是主题问题“增强作物光合作用：改进目标”的一部分。
Cyanobacteria are the most ancient organisms performing oxygenic photosynthesis, and they are the ancestors of plant plastids. All plastids contain the plastid terminal oxidase (PTOX), while only certain cyanobacteria contain PTOX. Many putative functions have been discussed for PTOX in higher plants including a photoprotective role during abiotic stresses like high light, salinity and extreme temperatures. Since PTOX oxidizes PQH(2) and reduces oxygen to water, it is thought to protect against photo-oxidative damage by removing excess electrons from the plastoquinone (PQ) pool. To investigate the role of PTOX we overexpressed rice PTOX fused to the maltose-binding protein (MBP-OsPTOX) in Synechocystis sp. PCC 6803, a model cyanobacterium that does not encode PTOX. The fusion was highly expressed and OsPTOX was active, as shown by chlorophyll fluorescence and P-700 absorption measurements. The presence of PTOX led to a highly oxidized state of the NAD(P) H/NAD(P)(+) pool, as detected by NAD(P)H fluorescence. Moreover, in the PTOX overexpressor the electron transport capacity of PSI relative to PSII was higher, indicating an alteration of the photosystem I (PSI) to photosystem II (PSII) stoichiometry. We suggest that PTOX controls the expression of responsive genes of the photosynthetic apparatus in a different way from the PQ/PQH(2) ratio.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.