Long-Term Acclimation of the Cyanobacterium Synechocystis sp PCC 6803 to High Light Is Accompanied by an Enhanced Production of Chlorophyll That Is Preferentially Channeled to Trimeric Photosystem I
Long-Term Acclimation of the Cyanobacterium Synechocystis sp PCC 6803 to High Light Is Accompanied by an Enhanced Production of Chlorophyll That Is Preferentially Channeled to Trimeric Photosystem I
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DOI：
10.1104/pp.112.207274
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发表时间：
2012-12-01
期刊：
影响因子：
7.4
通讯作者：
Sobotka, Roman
中科院分区：
文献类型：
--
作者：
Kopecna, Jana;Komenda, Josef;Sobotka, Roman
蓝细菌通过降低类囊体膜中光系统I（PSI）的丰度来调节光系统的化学计量来适应强光条件。由于PSI复合物结合蓝藻细胞中的大部分叶绿素（Chl），因此控制PSI水平/合成的机制与Chl生物合成途径紧密相关。然而，在不同的光照条件下，叶绿素是如何分布到光系统中的仍然是未知的。使用放射性标记的S-35和C-14结合本地/二维电泳，我们评估了合成和积累的光合复合物的合成与叶绿素的合成在集胞藻属PCC 6803细胞适应不同的光强度。虽然细胞适应较高的辐照度（150和300 μ E m（-2）s（-1））表现出显着减少PSI含量时，与细胞生长在较低的辐照度（10和40 μ E m（-2）s（-1））相比，他们生长得更快，并合成显着更多的叶绿素，以及两个光系统。有趣的是，即使在高辐射下，几乎所有标记的从头叶绿素定位在三聚体PSI，而只有一个弱的叶绿素标记的光系统II（PSII）伴随着密集的S-35蛋白标记，这是比PSI强得多。这些结果表明，PSII亚基主要是利用回收的叶绿素分子之前释放的PSII修复驱动的蛋白质降解合成。相比之下，大部分新鲜Chl用于合成PSI复合物，可能在细胞增殖期间维持恒定的PSI水平。
Cyanobacteria acclimate to high-light conditions by adjusting photosystem stoichiometry through a decrease of photosystem I (PSI) abundance in thylakoid membranes. As PSI complexes bind the majority of chlorophyll (Chl) in cyanobacterial cells, it is accepted that the mechanism controlling PSI level/synthesis is tightly associated with the Chl biosynthetic pathway. However, how Chl is distributed to photosystems under different light conditions remains unknown. Using radioactive labeling by S-35 and by C-14 combined with native/two-dimensional electrophoresis, we assessed the synthesis and accumulation of photosynthetic complexes in parallel with the synthesis of Chl in Synechocystis sp. PCC 6803 cells acclimated to different light intensities. Although cells acclimated to higher irradiances (150 and 300 mu E m(-2)s(-1)) exhibited markedly reduced PSI content when compared with cells grown at lower irradiances (10 and 40 mu E m(-2)s(-1)), they grew much faster and synthesized significantly more Chl, as well as both photosystems. Interestingly, even under high irradiance, almost all labeled de novo Chl was localized in the trimeric PSI, whereas only a weak Chl labeling in photosystem II (PSII) was accompanied by the intensive S-35 protein labeling, which was much stronger than in PSI. These results suggest that PSII subunits are mostly synthesized using recycled Chl molecules previously released during PSII repair-driven protein degradation. In contrast, most of the fresh Chl is utilized for synthesis of PSI complexes likely to maintain a constant level of PSI during cell proliferation.