Combined Increases in Mitochondrial Cooperation and Oxygen Photoreduction Compensate for Deficiency in Cyclic Electron Flow in Chlamydomonas reinhardtii
Combined Increases in Mitochondrial Cooperation and Oxygen Photoreduction Compensate for Deficiency in Cyclic Electron Flow in Chlamydomonas reinhardtii
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DOI：
10.1105/tpc.114.126375
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发表时间：
2014-07-01
期刊：
影响因子：
11.6
通讯作者：
Peltier, Gilles
中科院分区：
文献类型：
--
作者：
Dang, Kieu-Van;Plet, Julie;Peltier, Gilles
在产氧光合作用过程中，CO2固定的代谢反应需要比从光系统II到光系统I（PSI）的线性电子流所提供的更多的ATP。不同的机制，如PSI周围的循环电子流（CEF），已被提出参与重新平衡ATP/NADPH平衡。为了确定CEF对微藻生物量生产力的贡献，在这里，我们研究了质子梯度调节类似物1（PGRL 1）介导的CEF基因敲除莱茵衣藻突变体（pgrl 1）的光合作用和生长性能。稳态生物量生产力的pgrl 1突变体，在光生物反应器中作为turbidostats操作，是类似于其野生型的祖先在很宽的范围内的照明和CO2浓度。在pgrl 1中观察到几个变化，包括光合作用对线粒体抑制剂的敏感性更高，光依赖性O-2吸收增加，以及黄二铁（FLV）蛋白的量增加。我们得出结论，PSI（Mehler反应）的线粒体合作和氧光还原下游的组合提供额外的ATP的光合作用在pgrl 1突变体，导致在稳态条件下正常的生物质生产力。在pgrl 1突变体中观察到的较低的生物量生产率在波动的光归因于补偿机制无法响应ATP需求的快速增加。
During oxygenic photosynthesis, metabolic reactions of CO2 fixation require more ATP than is supplied by the linear electron flow operating from photosystem II to photosystem I (PSI). Different mechanisms, such as cyclic electron flow (CEF) around PSI, have been proposed to participate in reequilibrating the ATP/NADPH balance. To determine the contribution of CEF to microalgal biomass productivity, here, we studied photosynthesis and growth performances of a knockout Chlamydomonas reinhardtii mutant (pgrl1) deficient in PROTON GRADIENT REGULATION LIKE1 (PGRL1)-mediated CEF. Steady state biomass productivity of the pgrl1 mutant, measured in photobioreactors operated as turbidostats, was similar to its wild-type progenitor under a wide range of illumination and CO2 concentrations. Several changes were observed in pgrl1, including higher sensitivity of photosynthesis to mitochondrial inhibitors, increased light-dependent O-2 uptake, and increased amounts of flavodiiron (FLV) proteins. We conclude that a combination of mitochondrial cooperation and oxygen photoreduction downstream of PSI (Mehler reactions) supplies extra ATP for photosynthesis in the pgrl1 mutant, resulting in normal biomass productivity under steady state conditions. The lower biomass productivity observed in the pgrl1 mutant in fluctuating light is attributed to an inability of compensation mechanisms to respond to a rapid increase in ATP demand.