Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, 6726 Szeged, Hungary.
Climate Change Cluster, University of Technology Sydney, Ultimo, NSW 2007, Australia.
Int J Mol Sci. 2022 Apr 28;23(9):4927. doi: 10.3390/ijms23094927.
Photosynthesis is a series of redox reactions, in which several electron transport processes operate to provide the energetic balance of light harvesting. In addition to linear electron flow, which ensures the basic functions of photosynthetic productivity and carbon fixation, alternative electron transport pathways operate, such as the cyclic electron flow (CEF), which play a role in the fine tuning of photosynthesis and balancing the ATP/NADPH ratio under stress conditions. In this work, we characterized the electron transport processes in microalgae species that have high relevance in applied research and industry (e.g., , , , sp.) by using flash-induced fluorescence relaxation kinetics. We found that a wave phenomenon appeared in the fluorescence relaxation profiles of microalgae to different extents; it was remarkable in the red cells of , and , but it was absent in green cells of and . Furthermore, in microalgae, unlike in cyanobacteria, the appearance of the wave required the partial decrease in the activity of Photosystem II, because the relatively high Photosystem II/Photosystem I ratio in microalgae prevented the enhanced oxidation of the plastoquinone pool. The wave phenomenon was shown to be related to the antimycin A-sensitive pathway of CEF in but not in other species. Therefore, the fluorescence wave phenomenon appears to be a species-specific indicator of the redox reactions of the plastoquinone pool and certain pathways of cyclic electron flow.
光合作用是一系列氧化还原反应，其中几个电子传递过程协同作用以提供光能的能量平衡。除了确保光合作用生产力和碳固定基本功能的线性电子流外，还存在替代的电子传递途径，如循环电子流（CEF），它们在光合作用的微调以及在胁迫条件下平衡 ATP/NADPH 比方面发挥作用。在这项工作中，我们通过使用闪光诱导荧光弛豫动力学来描述在应用研究和工业中具有高度相关性的微藻物种中的电子传递过程（例如，，，，sp.）。我们发现，荧光弛豫谱中的波现象在不同程度上出现在微藻中；在 、和 的红色细胞中非常显著，但在 和 的绿色细胞中则不存在。此外，与蓝藻不同，在微藻中，波的出现需要部分降低光系统 II 的活性，因为微藻中相对较高的光系统 II/光系统 I 比阻止了质体醌库的增强氧化。波现象被证明与 中的抗霉素 A 敏感的 CEF 途径有关，但在其他物种中则没有。因此，荧光波现象似乎是质体醌库的氧化还原反应和某些循环电子流途径的种特异性指标。
