Interruption of the Calvin cycle inhibits the repair of Photosystem II from photodamage.
Interruption of the Calvin cycle inhibits the repair of Photosystem II from photodamage.
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DOI：
10.1016/j.bbabio.2005.04.003
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发表时间：
2005-07
期刊：
影响因子：
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通讯作者：
S. Takahashi;N. Murata
中科院分区：
文献类型：
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作者：
S. Takahashi;N. Murata
在光合生物中，卡尔文循环中酶活性的损害增加了光系统II （PSII）的光失活程度。我们在单细胞绿藻莱茵衣藻中研究了导致这一现象的分子机制。当卡尔文循环被已知可抑制磷酸脲激酶的乙醇醛打断时，PSII的光失活程度增强。乙醇醛的作用与氯霉素非常相似，都能抑制叶绿体中蛋白质的新生合成。通过引入核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）大亚基的错义突变而中断卡尔文循环也增强了PSII的光失活程度。在这种突变的10-6C细胞中，乙醇醛和氯霉素对光失活都没有任何额外的影响。PSII光损伤后，野生型细胞在弱光下孵育，PSII活性逐渐恢复，达到接近初始水平。然而，乙醇醛抑制野生型细胞的恢复，也抑制10-6C细胞的恢复。放射性标记和Northern印迹表明，卡尔文循环的中断抑制了叶绿体蛋白（如D1和D2蛋白）的新生合成，但不影响psbA和psbD mrna的水平。我们的研究结果表明，与卡尔文循环中断相关的PSII光失活主要归因于叶绿体翻译水平上PSII蛋白合成依赖性修复的抑制。
In photosynthetic organisms, impairment of the activities of enzymes in the Calvin cycle enhances the extent of photoinactivation of Photosystem II (PSII). We investigated the molecular mechanism responsible for this phenomenon in the unicellular green alga Chlamydomonas reinhardtii. When the Calvin cycle was interrupted by glycolaldehyde, which is known to inhibit phosphoribulokinase, the extent of photoinactivation of PSII was enhanced. The effect of glycolaldehyde was very similar to that of chloramphenicol, which inhibits protein synthesis de novo in chloroplasts. The interruption of the Calvin cycle by the introduction of a missense mutation into the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) also enhanced the extent of photoinactivation of PSII. In such mutant 10-6C cells, neither glycolaldehyde nor chloramphenicol has any additional effect on photoinactivation. When wild-type cells were incubated under weak light after photodamage to PSII, the activity of PSII recovered gradually and reached a level close to the initial level. However, recovery was inhibited in wild-type cells by glycolaldehyde and was also inhibited in 10-6C cells. Radioactive labelling and Northern blotting demonstrated that the interruption of the Calvin cycle suppressed the synthesis de novo of chloroplast proteins, such as the D1 and D2 proteins, but did not affect the levels of psbA and psbD mRNAs. Our results suggest that the photoinactivation of PSII that is associated with the interruption of the Calvin cycle is attributable primarily to the inhibition of the protein synthesis-dependent repair of PSII at the level of translation in chloroplasts.