Institute of Molecular Biosciences, Department of Biosciences, University of Frankfurt, Frankfurt, Germany.
J Exp Bot. 2012 Jun;63(10):3673-81. doi: 10.1093/jxb/ers049. Epub 2012 Mar 21.
Analysis of photosystem I (PSI) complexes from Cyclotella meneghiniana cultured under different growth conditions led to the identification of three groups of antenna proteins, having molecular weights of around 19, 18, and 17 kDa. The 19-kDa proteins have earlier been demonstrated to be more peripherally bound to PSI, and their amount in the PSI complexes was significantly reduced when the iron supply in the growth medium was lowered. This polypeptide was almost missing, and thus the total amount of fucoxanthin-chlorophyll proteins (Fcps) bound to PSI was reduced as well. When treating cells with high light in addition, no further changes in antenna polypeptide composition were detected. Xanthophyll cycle pigments were found to be bound to all Fcps of PSI. However, PSI of high light cultures had a significantly higher diatoxanthin to diadinoxanthin ratio, which is assumed to protect against a surplus of excitation energy. PSI complexes from the double-stressed cultures (high light plus reduced iron supply) were slightly more sensitive against destruction by the detergent treatment. This could be seen as a higher 674-nm emission at 77 K in comparison to the PSI complexes isolated from other growth conditions. Two major emission bands of the Fcps bound to PSI at 77 K could be identified, whereby chlorophyll a fluorescing at 697 nm was more strongly coupled to the PSI core than those fluorescing at 685 nm. Thus, the build up of the PSI antenna of several Fcp components enables variable reactions to several stress factors commonly experienced by the diatoms in vivo, in particular diatoxanthin enrichment under high light and reduction of antenna size under reduced iron conditions.
对在不同生长条件下培养的Cyclotella meneghiniana 的光系统 I（PSI）复合物进行分析，导致鉴定出三组天线蛋白，分子量约为 19、18 和 17 kDa。先前已经证明 19 kDa 的蛋白质更靠近 PSI 外周结合，并且当生长培养基中的铁供应降低时，PSI 复合物中这种多肽的含量显着降低。这种多肽几乎不存在，因此与 PSI 结合的叶黄素-叶绿素蛋白（Fcps）的总量也减少了。此外，当用高光处理细胞时，没有检测到天线多肽组成的进一步变化。发现叶黄素循环色素与 PSI 的所有 Fcps 结合。然而，高光培养的 PSI 具有明显更高的二氢玉米黄质与玉米黄质的比值，这被认为可以防止过剩的激发能量。来自双重胁迫培养（高光加铁供应减少）的 PSI 复合物对去污剂处理的破坏略为敏感。与从其他生长条件分离的 PSI 复合物相比，这可以在 77 K 下以 674nm 发射更高的 674nm 发射看出。可以在 77 K 下鉴定出结合到 PSI 的 Fcps 的两个主要发射带，其中在 697nm 处荧光的叶绿素 a 比在 685nm 处荧光的叶绿素 a 更强烈地与 PSI 核心耦合。因此，几个 Fcp 成分的 PSI 天线的构建能够对真核生物中硅藻通常经历的几种胁迫因素做出可变反应，特别是高光下二氢玉米黄质的富集和铁减少条件下天线大小的减少。
