Université Paris-Saclay, CNRS, CEA, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif sur Yvette, France.
Photochem Photobiol Sci. 2020 May 1;19(5):585-603. doi: 10.1039/c9pp00451c. Epub 2020 Mar 12.
Photosynthetic organisms are exposed to a fluctuating environment in which light intensity and quality change continuously. Specific illumination of either photosystem (PSI or PSII) creates an energy imbalance, leading to the reduction or oxidation of the intersystem electron transport chain. This redox imbalance could trigger the formation of dangerous reactive oxygen species. Cyanobacteria, like plants and algae, have developed a mechanism to re-balance this preferential excitation of either reaction center, called state transitions. State transitions are triggered by changes in the redox state of the membrane-soluble plastoquinone (PQ) pool. In plants and green algae, these changes in redox potential are sensed by Cytochrome bf, which interacts with a specific kinase that triggers the movement of the main PSII antenna (the light-harvesting complex II). By contrast, although cyanobacterial state transitions have been studied extensively, there is still no agreement about the molecular mechanism, the PQ redox state sensor and the signaling pathways involved. In this review, we aimed to critically evaluate the results published on cyanobacterial state transitions, and discuss the "new" and "old" models in the subject. The phycobilisome and membrane contributions to this physiological process were addressed and the current hypotheses regarding its signaling transduction pathway were discussed.
光合生物暴露在不断变化的环境中，其中光强和光质不断变化。对光合作用系统 I（PSI）或光合作用系统 II（PSII）的特定照射会产生能量不平衡，导致两个光系统之间的电子传递链的还原或氧化。这种氧化还原失衡可能会引发危险的活性氧物质的形成。蓝藻与植物和藻类一样，已经开发出一种重新平衡这种优先激发任何一个反应中心的机制，称为状态转变。状态转变是由膜可溶性质体醌（PQ）池的氧化还原状态变化触发的。在植物和绿藻中，这些氧化还原电位的变化由细胞色素 bf 感知，细胞色素 bf 与一种特定的激酶相互作用，触发主要 PSII 天线（光捕获复合物 II）的运动。相比之下，尽管蓝藻的状态转变已经得到了广泛的研究，但关于涉及的分子机制、PQ 氧化还原状态传感器和信号转导途径，仍然没有达成一致。在这篇综述中，我们旨在批判性地评估已发表的关于蓝藻状态转变的研究结果，并讨论该主题的“新”和“旧”模型。我们还讨论了藻胆体和膜对这一生理过程的贡献，以及关于其信号转导途径的当前假说。
