Control of hydrogen photoproduction by the proton gradient generated by cyclic electron flow阅读笔记

Control of hydrogen photoproduction by the proton gradient generated by cyclic electron flow in Chlamydomonas reinhardtii 题目翻译：莱茵衣藻中通过环式电子传递产生的质子梯度控制光致产氢作者：摘要：阅读笔记：真核微藻的光致产氢，通过光合电子传递链和质体氢化酶之间的联系：“Hydrogen photoproduction by eukaryotic microalgae results from a connection between the photosynthetic electron transport chain and a plastidial hydrogenase. ”藻类产氢，在自然条件下，通常是一种短暂的现象，通常被认为是一种避免光合电子传递链过度还原的一种保护安全阀：“Algal H2 production is a transitory phenomenon under most natural conditions, often viewed as a safety valve protecting the photosynthetic electron transport chain from overreduction. ”分析莱茵衣藻的突变株，基于暗-光叶绿素荧光分析，分离出一株环绕PSI的环式电子传递CEF 受损的突变株，由于其缺乏“质子梯度调节蛋白Proton Gradient Regulation Like1 (PGRL1) protein”：“From the colony screening of an insertion mutant library of the unicellular green algaChlamydomonas reinhardtii based on the analysis of dark-light chlorophyll fluorescence transients, we isolated a mutant impaired in cyclic electron flow around photosystem I (CEF) due to a defect in the Proton Gr adient Regulation Like1 (PGRL1) protein. ”在好氧生活条件下，在突变株pgrl1中，非光化学淬灭（NPQ）显著降低：“Under aerobiosis, nonphotochemical quenching of fluorescence (NPQ) is strongly decreased in pgrl1.”在厌氧生活条件下，在突变株pgrl1中的光致产氢显著增加，无论是在短期还是长期测量中（缺硫条件下）：“Under anaerobiosis, H2 photoproduction is strongly enhanced in the pgrl1 mutant, both during short-term and long-term measurements (in conditions of sulfur deprivation).”根据NPQ和产生氢气的光依赖性，同时，在加入解耦联剂FCCP（uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP)）时野生型的产氢量也增加，得出结论：CEF产生的质子梯度引起野生型中氢化酶的电子供应抑制，而在突变株pgrl1中是没有这种抑制的：“Based on the light dependence of NPQ and hydrogen production, as well as on the enhanced hydrogen production observed in the wild-type strain in the presence of the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone, we conclude that the proton gradient generated by CEF provokes a strong inhibition of electron supply to the hydrogenase in the wild-type strain, which is released in the pgrl1 mutant.”通过检测pgrl1的表达对跨类囊体膜质子梯度的调节，展示了重新设计微藻细胞的代谢来增加氢气生产量的新视野：“Regulation of thetrans-thylakoidal proton gradient by monitoring pgrl1 expression opens new perspectives toward reprogramming the cellular metabolism of microalgae for enhanced H2 production.”模式生物莱茵衣藻在产氢中的研究应用：“A few microalgae species, including the model species Chlamydomonas reinhardtii , have been reported to produce H2 in the light (Gaffron and Rubin, 1942; Healey, 1970)”藻类产氢的过程（WX）：“During this process, electrons produced by the photosynthetic electron transport chain are diverted at the level of ferredoxin toward [Fe-Fe] hydrogenase, which catalyzes the reversible reduction of protons into molecular hydrogen in algae (Florin et al., 2001).”藻类产氢优势/前景（WX）：“The use of microalgae is considered to be a promising approach for developing sustainable H2 production from sunlight energy and water as the main resources (Melis and Happe, 2001).”藻类产氢开发的障碍，增加产量和控制（WX）：“Harnessing and enhancing microalgal H2 production is recognized as a major step in developing clean and sustainable hydrogen economy (Ghirardi etal., 2000; Melis, 2002; Kruse et al., 2005a).”产氢过程的主要限制：光合产的氧使敏感的产氢的氢化酶失活：“Themain limitation to hydrogenproduction is considered to resultfrom the O2 sensitivity ofhydrogenase enzymes: molecular O2produced at photosystem II (PSII)during photosynthesis rapidlyinduces the irreversible inhibition ofthe algal [FeFe]-hydrogenase (Happeet al., 2002; Stripp et al., 2009).”实验操作发现，缺硫可以避免这种情况，通过产氧气和产氢气的阶段在时间上分离：“An experimentalprotocol based on sulfur deficiencywas reported to circumvent thislimitation by inducing a time-basedseparation of O2- and H2-producingphases (Melis et al., 2000). ”解释：在好氧时，光合作用的还原力以淀粉形式贮存，在之后厌氧时通过产生氢气或在线粒体进行呼吸作用维持厌氧环境（WX。

）：“Duringthis process, the reducing powergenerated by photosynthesis istemporarily stored as starch duringthe aerobic phase and consumedduring a subsequent anaerobicperiod to supply reductants either toproduce H2 or to maintainanaerobiosis by feedingmitochondrial respiration (Melis et al.,2000; Chochois et al., 2009).”其他一些实验通过基因手段降低氢化酶对氧气的活性：“Other experimental approaches have used genetic engineering aiming at lowering the O2 sensitivity of hydrogenase.”在产氢气时两条电子传递的途径（在缺硫的情况下）：一条是“直接的途径”：电子来自光合过程中从PSII传递到PSI的电子，之后经过【还原态铁氧还蛋白】传递到氢化酶；在“间接途径”中：光合作用的还原力首先由于缺硫而贮存为淀粉starch，淀粉分解作用的还原当量进入系统间的电子传递链质体醌库plastoquinone (PQ) pool，现已发现此过程中的酶（WX。

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“Two main pathways of electron supply have been previously identified under conditions of sulfur limitation, a direct and an indirect pathway (Fouchard et al., 2005; Chochois et al., 2009). During the direct pathway, hydrogen is produced using electrons supplied by the photosynthetic electron transport chain from PSII to photosystem I (PSI) and then to the hydrogenase via reduced ferredoxin. During the indirect pathway, the reducing power generated by oxygenic photosynthesis, first stored as starchin response to sulfur starvation, is remobilized in a second step. During this process, the reducing equivalents generated during starch catabolism are injected into the intersystem electron transport chain at the level of the plastoquinone (PQ) pool. The enzyme involved in this process has recently been identified as a plastidial type II NADH dehydrogenase called Nda2 (Jans et al., 2008; Desplats et al., 2009).”这两种途径都公用的电子载体有：cytochrome b6/f complex, plastocyanin, and PSI（注意，当然还有PQ库）：“Both pathways of hydrogen production share common electron carriers, such as the cytochrome b6/f co mplex, plastocyanin, and PSI.”【CEF】产生跨类囊体膜质子梯度，促进建立NPQ：“CEF has been shownto generate a thylakoidtrans-membrane proton gradientinvolved in the establishment ofnonphotochemical quenching(NPQ).”在衣藻中，CEF受到状态转换的调控，这包含在激发能在PSI与PSII之间的再分配：“In Chlamydomonas, CEF isregulated by state transition (Finazziet al., 2002), a phenomenoninvolved in the redistribution of theexcitation energy between PSI andPSII.”状态转换1→2：发生在PQ库的氧环状态增加时，如：在厌氧条件下：“Transition from state 1 to state 2occurs in response to an increase inthe redox state of the PQ pool, for instance, under anaerobic conditions. ”诱导了STT7 激酶的激发来磷酸化可移动的LHCII从PSII 向PSI移动（WX）：“This triggers the STT7 kinase to phosphorylate mobile light-harvesting complex II (LHCII), resulting in a move of phosphorylated LHCII from PSII to PSI (Depège et al., 2003). ”CEF的调控蛋白：PGR5 和后来发现的PGRL1，后者可以与PGR5 和铁氧还蛋白相互作用（WX）：“PGR5 was first identified in Arabidopsis thaliana as an essential molecular component of CEF from a screen of Arabidopsis mutants affected in NPQ (Munekage et al., 2002). More recently, Proton Gradient Regulation Like1 (PGRL1) has been identified in Arabidopsis as another essential component of CEF, inte racting with both PGR5 and ferredoxin (DalCorso et al., 2008).”CEF的调控蛋白：PGR5和后来发现的PGRL1，后者可以与PGR5 和铁氧还蛋白相互作用（WX）：“PGR5 wasfirst identified inArabidopsis thaliana asan essential molecularcomponent of CEFfrom a screen ofArabidopsis mutantsaffected in NPQ(Munekage et al.,2002). More recently,Proton GradientRegulation Like1(PGRL1) has beenidentified inArabidopsis as anotheressential componentof CEF, interacting withboth PGR5 andferredoxin (DalCorsoet al., 2008).”在莱茵衣藻中，PGRL1 的下行调节使CEF受损，特别是在缺铁的条件下（WX）：“In C. reinhardtii,downregulation of PGRL1 resulted in an impairment of CEF, particularly under conditions of iron deficiency (Petroutsos et al., 2009).”【结果】：①突变体的ETR和NPQ结果：图1B，单独做的荧光信号的“暗-光-暗”的记录：“ a dark-light-dark transient”图1F、G，a dark-light transient过程的每次打饱和光测定ETR和NPQ，类似IC测量；★结果：突变体的荧光信号的“暗-光-暗”动力学曲线变化，突变体的ETR高，而NPQ低；“Whereas the ETR was higher in the pgrl1 mutant than in the wild type (Figure 1F), NPQ remained lower (Figure 1G). ”图2D and 2E，ETR和NPQ的光响应曲线的测量/ 光响应曲线光强应用：“ETR (图2D) and NPQ(图2E) determined from chlorophyll fluorescence measurements performed on light-adapted cells after 40 s of illumination at each given fluence.”图1：“The ETR reached similar ★结果：ETR在突变和野生型之间差异不明显，而突变株的NPQ显著降低：values in pgrl1 and in the wild type under a wide range of light intensities (Figure 2D). By contrast, NPQ was strongly diminished in pgrl1 (Figure 2E).”原因解释：CEF损伤，跨膜质子梯度不足：如：（WX）之前在PGR5 and PGRL1 genes突变体的拟南芥中叶发现NPQ的显著降低，是由于缺少光诱导的质子梯度，而这是由于CEF的受损：“Strongly reduced NPQ ability was previously reported in Arabidopsis mutants affected in PGR5 and PGRL1 genes and was attributed to the existence of a lower light-induced proton gradient resulting from CEF impairment (Munekage et al., 2002; DalCorso et al., 2008). ”②突变体的CEF结果：【CEF测量】两种方法（WX。