Flavodiiron Proteins Promote Fast and Transient O2 Photoreduction in Chlamydomonas1[OPEN]
Flavodiiron Proteins Promote Fast and Transient O2 Photoreduction in Chlamydomonas1[OPEN]
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DOI：
10.1104/pp.17.00421
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发表时间：
2017-07-01
期刊：
影响因子：
7.4
通讯作者：
Peltier, Gilles
中科院分区：
文献类型：
--
作者：
Chaux, Frederic;Burlacot, Adrien;Peltier, Gilles
产氧光合作用时，光能转换产生的还原力主要用于还原二氧化碳。在细菌和古细菌中，黄二铁 (Flv) 蛋白催化 O-2 或 NO 还原，从而保护细胞免受氧化或亚硝化应激。这些蛋白质存在于蓝藻、苔藓和微藻中，但在被子植物中丢失了。在这里，我们使用 [O-18] 标记的 O-2 和膜入口质谱仪进行叶绿素荧光和氧交换测量，以表征缺乏 FlvB 和 FlvA 蛋白的莱茵衣藻 flvB 插入突变体。我们发现，Flv 蛋白参与流向氧气的光依赖性电子流，在光合作用诱导过程中驱动大部分光合电子流。因此，flvB 突变体的叶绿素荧光模式在光瞬变期间受到强烈影响，显示出较低的 PSII 操作产量和较慢的非光化学猝灭诱导。 flvB 突变体的光自养生长在恒定光下与野生型没有区别，但在波动光下由于 PSI 光损伤而严重受损。值得注意的是，在波动光照条件的最初几个小时内，flvB突变体的净光合作用高于野生型，但这种优势在长期暴露下消失，并转化为PSI光损伤，从而解释了在这些条件下观察到的明显生长迟缓。我们得出的结论是，莱茵衣藻 Flv 参与了 O-2 的类似 Mehler 还原，这在光瞬变期间驱动了大部分光合电子流，因此对于波动光状态下的生长至关重要。
During oxygenic photosynthesis, the reducing power generated by light energy conversion is mainly used to reduce carbon dioxide. In bacteria and archae, flavodiiron (Flv) proteins catalyze O-2 or NO reduction, thus protecting cells against oxidative or nitrosative stress. These proteins are found in cyanobacteria, mosses, and microalgae, but have been lost in angiosperms. Here, we used chlorophyll fluorescence and oxygen exchange measurement using [O-18]-labeled O-2 and a membrane inlet mass spectrometer to characterize Chlamydomonas reinhardtii flvB insertion mutants devoid of both FlvB and FlvA proteins. We show that Flv proteins are involved in a photo-dependent electron flow to oxygen, which drives most of the photosynthetic electron flow during the induction of photosynthesis. As a consequence, the chlorophyll fluorescence patterns are strongly affected in flvB mutants during a light transient, showing a lower PSII operating yield and a slower nonphotochemical quenching induction. Photoautotrophic growth of flvB mutants was indistinguishable from the wild type under constant light, but severely impaired under fluctuating light due to PSI photo damage. Remarkably, net photosynthesis of flvB mutants was higher than in the wild type during the initial hour of a fluctuating light regime, but this advantage vanished under long-term exposure, and turned into PSI photo damage, thus explaining the marked growth retardation observed in these conditions. We conclude that the C. reinhardtii Flv participates in a Mehler-like reduction of O-2, which drives a large part of the photosynthetic electron flow during a light transient and is thus critical for growth under fluctuating light regimes.