NAD(P)H Dehydrogenase-Dependent Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechocystis PCC 6803: a Study of Dark-Starved Cells and Spheroplasts
NAD(P)H Dehydrogenase-Dependent Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechocystis PCC 6803: a Study of Dark-Starved Cells and Spheroplasts
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DOI：
10.1093/oxfordjournals.pcp.a078580
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发表时间：
1994
影响因子：
4.9
通讯作者：
H. Mi;T. Endo;U. Schreiber;T. Ogawa;K. Asada
中科院分区：
文献类型：
--
作者：
H. Mi;T. Endo;U. Schreiber;T. Ogawa;K. Asada
通过呼吸底物和PSI中的光还原剂通过系间链中的质醌向P700+供电子，已被证明是由集胞体PCC6803细胞中的NAD(P)H-脱氢酶复合体(NDH)介导的[Mi等人]。(1992)植物细胞生理学。33：1233]。为了证实NDH参与了PSI周围的循环电子流动，分析了暗饥饿导致呼吸底物缺乏的细胞和球体中P700和CHI荧光的氧化还原动力学。暗饥饿的细胞在远红光(FR)照射下显示出高水平的P700+稳态水平，质醌池处于高度氧化状态。一个NDH缺陷突变体在黑暗饥饿前后的FR下始终表现出高水平的P700氧化。利用野生型细胞的球形体，证明了外源NADPH或光还原的NADPH+的电子通过叶绿体递送到系统间链，而来自NDH缺陷突变体的球体则没有，这是通过CHI荧光动力学和P700的氧化还原状态的变化来监测的。线粒体NDH和琥珀酸脱氢酶的抑制剂鱼藤酮、Hg2+离子和2-噻吩甲酰三氟丙酮对NADPH介导的电子流向PSI很敏感，但对抗霉素A不敏感。细胞质中可通过光化光照射P700+的电子池大小随着光照时间的延长而增加，在野生型细胞和球体中对鱼藤酮都敏感，但在聚合胞6803的NDH缺陷突变体中没有得到这样的结果。这些结果支持了我们先前的结论，即NDH是蓝藻聚球藻呼吸电子流和从PSI到系统间链的循环电子流的中介体。
Electron donation to P700+through plastoquinone in the intersystem chain from both respiratory substrates and the photoreductants in PSI has been shown to be mediated by the NAD(P)H-dehydrogenase complex (NDH) inSynechocystisPCC 6803 cells [Mi et al. (1992)Plant Cell Physiol. 33: 1233]. To confirm the participation of NDH in the cyclic electron flow around PSI, the redox kinetics of P700 and Chi fluorescence were analyzed in cells rendered deficient in respiratory substrates by dark starvation and in spheroplasts.Dark-starved cells showed a high steady-state level of P700+under far-red (FR) illumination and the plastoquinone pool was in a highly oxidized state. An NDH-defective mutant consistently showed a high level of P700 oxidation under FR before and after the dark starvation. Donation of electrons either from exogenous NADPH or from photoreduced NADPH+to the intersystem chain via plastoquinone was demonstrated using spheroplasts from wild-type cells, but not those from the NDH-defective mutant, as monitored by following changes in the kinetics of Chi fluorescence and the redox state of P700. The electron flow to PSI via plastoquinone, mediated by NADPH, was sensitive to rotenone, Hg2+ions and 2-thenoyltrifluoroacetone, inhibitors of mitochondrial NDH and succinate dehydrogenase, but not to antimycin A. The pool size of electrons that can be donated to P700+from the cytosol through the intersystem chain increased with increasing duration of illumination time by actinic light and was sensitive to rotenone in both wild-type cells and spheroplasts, but no such results were obtained in the NDH-defective mutant ofSynechocystis6803. The results support our previous conclusion that NDH is a mediator of both respiratory electron flow and cyclic electron flow around PSI to the intersystem chain in the cyanobacteriumSynechocystis.