Inhibition of CO2 fixation by iodoacetamide stimulates cyclic electron flow and non-photochemical quenching upon far-red illumination
Inhibition of CO2 fixation by iodoacetamide stimulates cyclic electron flow and non-photochemical quenching upon far-red illumination
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DOI：
10.1007/s11120-013-9826-1
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发表时间：
2013-05-01
影响因子：
3.7
通讯作者：
Alric, Jean
中科院分区：
文献类型：
--
作者：
Joliot, Pierre;Alric, Jean
当二硫键通过叶绿体中的铁氧还蛋白-硫氧还蛋白系统还原而打开时，本森-卡尔文循环酶在体内被激活。碘乙酰胺与半胱氨酸残基的游离 -SH 基团发生不可逆反应，并抑制负责 CO2 固定的酶。在这里，我们研究了碘乙酰胺渗入菠菜叶时对电子传输的影响。使用荧光和吸收光谱，我们表明（i）碘乙酰胺在两个光系统照射时非常有效地阻止线性电子流（光系统II的光化学产率降低）和（ii）碘乙酰胺有利于PSI特有的光激发时的循环电子流。这些效应使得碘乙酰胺在远红光照射下比在饱和光下的对照中更快地形成 NPQ。 NPQ 的这种增加取决于类囊体膜上的质子梯度（通过添加尼日利亚霉素解偶联）和 PGR5（拟南芥 pgr5 突变体中不存在）。碘乙酰胺非常紧密地隔离类囊体膜水平的电子流，防止任何电子泄漏到碳代谢，因此，为研究 PSI 周围的循环电子流提供了选择条件。
The Benson-Calvin cycle enzymes are activated in vivo when disulfide bonds are opened by reduction via the ferredoxin-thioredoxin system in chloroplasts. Iodoacetamide reacts irreversibly with free -SH groups of cysteine residues and inhibits the enzymes responsible for CO2 fixation. Here, we investigate the effect of iodoacetamide on electron transport, when infiltrated into spinach leaves. Using fluorescence and absorption spectroscopy, we show that (i) iodoacetamide very efficiently blocks linear electron flow upon illumination of both photosystems (decrease in the photochemical yield of photosystem II) and (ii) iodoacetamide favors cyclic electron flow upon light excitation specific to PSI. These effects account for an NPQ formation even faster in iodoacetamide under far-red illumination than in the control under saturating light. Such an increase in NPQ is dependent upon the proton gradient across the thylakoid membrane (uncoupled by nigericin addition) and PGR5 (absent in Arabidopsis pgr5 mutant). Iodoacetamide very tightly insulates the electron current at the level of the thylakoid membrane from any electron leaks toward carbon metabolism, therefore, providing choice conditions for the study of cyclic electron flow around PSI.