How Does Cyclic Electron Flow Alleviate Photoinhibition in Arabidopsis?1[W][OA]
How Does Cyclic Electron Flow Alleviate Photoinhibition in Arabidopsis?1[W][OA]
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DOI：
10.1104/pp.108.134122
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发表时间：
2008-12
期刊：
影响因子：
7.4
通讯作者：
S. Takahashi;Sara E. Milward;Da-Yong Fan;W. Chow;M. Badger
中科院分区：
文献类型：
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作者：
S. Takahashi;Sara E. Milward;Da-Yong Fan;W. Chow;M. Badger
围绕光系统I的循环电子流（CEF）在避免光系统II（PSII）的光抑制方面具有作用，光抑制发生在PSII的光损伤速率超过其修复速率的条件下。然而，CEF如何有助于光保护的分子机制尚未得到很好的理解。我们利用暴露在强光下的拟南芥（Arabidopsis thaliana）的CEF（pgr5）和热能耗散（qE）（npq1和npq4）突变体，研究了CEF受损和热能耗散受损对光抑制的影响。pgr5突变导致的CEF受损抑制了qE并加速了光抑制。我们发现，pgr5、npq1和npq4突变导致的qE受损，在D1蛋白从头合成步骤抑制了光损伤PSII的修复。在存在叶绿体蛋白质合成抑制剂氯霉素的情况下，CEF受损（而非qE受损）加速了光抑制，当叶片用质子载体尼日利亚菌素渗透时也得到了类似的效果。这些结果表明，类囊体膜上依赖CEF产生的ΔpH通过至少两种不同的光保护机制有助于减轻光抑制：一种与qE产生相关，防止在蛋白质合成步骤抑制光损伤PSII的修复；另一种与qE无关，抑制对PSII的光损伤。
Cyclic electron flow (CEF) around photosystem I has a role in avoiding photoinhibition of photosystem II (PSII), which occurs under conditions in which the rate of photodamage to PSII exceeds the rate of its repair. However, the molecular mechanism underlying how CEF contributes to photoprotection is not yet well understood. We examined the effect of impairment of CEF and thermal energy dissipation (qE) on photoinhibition using CEF (pgr5) and qE (npq1 and npq4) mutants of Arabidopsis (Arabidopsis thaliana) exposed to strong light. Impairment of CEF by mutation of pgr5 suppressed qE and accelerated photoinhibition. We found that impairment of qE, by mutations of pgr5, npq1, and npq4, caused inhibition of the repair of photodamaged PSII at the step of the de novo synthesis of the D1 protein. In the presence of the chloroplast protein synthesis inhibitor chloramphenicol, impairment of CEF, but not impairment of qE, accelerated photoinhibition, and a similar effect was obtained when leaves were infiltrated with the protonophore nigericin. These results suggest that CEF-dependent generation of ΔpH across the thylakoid membrane helps to alleviate photoinhibition by at least two different photoprotection mechanisms: one is linked to qE generation and prevents the inhibition of the repair of photodamaged PSII at the step of protein synthesis, and the other is independent of qE and suppresses photodamage to PSII.