Bioenergy and Defense Technologies, Sandia National Laboratories, Albuquerque, NM, 87123, USA.
Department of Biology, Washington University, St. Louis, MO, 63130, USA.
Photosynth Res. 2017 Nov;134(2):165-174. doi: 10.1007/s11120-017-0422-7. Epub 2017 Jul 21.
Cyanobacterial phycobilisome (PBS) pigment-protein complexes harvest light and transfer the energy to reaction centers. Previous ensemble studies have shown that cyanobacteria respond to changes in nutrient availability by modifying the structure of PBS complexes, but this process has not been visualized for individual pigments at the single-cell level due to spectral overlap. We characterized the response of four key photosynthetic pigments to nitrogen depletion and repletion at the subcellular level in individual, live Synechocystis sp. PCC 6803 cells using hyperspectral confocal fluorescence microscopy and multivariate image analysis. Our results revealed that PBS degradation and re-synthesis comprise a rapid response to nitrogen fluctuations, with coordinated populations of cells undergoing pigment modifications. Chlorophyll fluorescence originating from photosystem I and II decreased during nitrogen starvation, but no alteration in subcellular chlorophyll localization was found. We observed differential rod and core pigment responses to nitrogen deprivation, suggesting that PBS complexes undergo a stepwise degradation process.
蓝藻藻胆体（PBS）色素-蛋白复合物吸收光并将能量转移到反应中心。以前的整体研究表明，蓝藻通过改变 PBS 复合物的结构来响应养分可用性的变化，但由于光谱重叠，这个过程在单细胞水平上无法对单个色素进行可视化。我们使用超高分辨率共聚焦荧光显微镜和多元图像分析，在单个活的集胞藻 PCC 6803 细胞中，在亚细胞水平上对四种关键光合作用色素对氮饥饿和补充的反应进行了表征。我们的结果表明，PBS 的降解和重新合成是对氮波动的快速反应，伴随着细胞群体中色素修饰的协调进行。在氮饥饿期间，来自光系统 I 和 II 的叶绿素荧光减少，但未发现亚细胞叶绿素定位的改变。我们观察到对氮缺乏的杆状和核心色素的不同反应，表明 PBS 复合物经历了逐步降解过程。
