Dang Kieu-Van, Plet Julie, Tolleter Dimitri, Jokel Martina, Cuiné Stéphan, Carrier Patrick, Auroy Pascaline, Richaud Pierre, Johnson Xenie, Alric Jean, Allahverdiyeva Yagut, Peltier Gilles
CEA, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, CEA Cadarache, F-13108 Saint-Paul-lez-Durance, France CNRS, UMR 7265 Biologie Végétale et Microbiologie Environnementale, F-13108 Saint-Paul-lez-Durance, France Aix Marseille Université, UMR 7265 Biologie Végétale et Microbiologie Environnementale, F-13284 Marseille, France.
Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
Plant Cell. 2014 Jul;26(7):3036-50. doi: 10.1105/tpc.114.126375. Epub 2014 Jul 2.
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 O2 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.
在有氧光合作用过程中，二氧化碳固定的代谢反应所需的ATP比从光系统II到光系统I（PSI）的线性电子流所提供的ATP更多。已提出不同的机制，如PSI周围的循环电子流（CEF），参与重新平衡ATP/ NADPH的平衡。为了确定CEF对微藻生物量生产力的贡献，我们在此研究了缺乏质子梯度调节样蛋白1（PGRL1）介导的CEF的莱茵衣藻敲除突变体（pgrl1）的光合作用和生长性能。在作为浊度恒定器运行的光生物反应器中测量的pgrl1突变体的稳态生物量生产力，在广泛的光照和二氧化碳浓度下与其野生型亲本相似。在pgrl1中观察到了一些变化，包括光合作用对线粒体抑制剂的更高敏感性、光依赖性氧气吸收增加以及黄素二铁（FLV）蛋白量的增加。我们得出结论，线粒体协作和PSI下游的氧光还原（梅勒反应）的组合为pgrl1突变体的光合作用提供了额外的ATP，从而在稳态条件下产生正常的生物量生产力。在波动光下pgrl1突变体中观察到的较低生物量生产力归因于补偿机制无法应对ATP需求的快速增加。
