Smolinski Sharon L, Lubner Carolyn E, Guo Zhanjun, Artz Jacob H, Brown Katherine A, Mulder David W, King Paul W
National Renewable Energy Laboratory 15013 Denver West Parkway Golden CO 80401 USA
RSC Adv. 2022 May 16;12(23):14655-14664. doi: 10.1039/d2ra01295b. eCollection 2022 May 12.
The capacity of cyanobacteria to adapt to highly dynamic photon flux and nutrient availability conditions results from controlled management and use of reducing power, and is a major contributing factor to the efficiency of photosynthesis in aquatic environments. The response to changing conditions includes modulating gene expression and protein-protein interactions that serve to adjust the use of electron flux and mechanisms that control photosynthetic electron transport (PET). In this regard, the photochemical activity of photosystem I (PSI) reaction centers can support balancing of cyclic (CEF) and linear electron flow (LEF), and the coupling of redox carriers for use by electron utilization pathways. Therefore, changes in the utilization of reducing power might be expected to result in compensating changes at PSI as a means to support balance of electron flux. To understand this functional relationship, we investigated the properties of PSI and its photochemical activity in cells that lack flavodiiron 1 catalyzed oxygen reduction activity (ORR1). In the absence of ORR1, the oxygen evolution and consumption rates declined together with a shift in the oligomeric form of PSI towards monomers. The effect of these changes on PSI energy and electron transfer properties was examined in isolated trimer and monomer fractions of PSI reaction centers. Collectively, the results demonstrate that PSI photochemistry is modulated through coordination with the depletion of electron demand in the absence of ORR1.
蓝细菌适应高度动态的光子通量和养分可利用性条件的能力源于对还原力的可控管理和利用，并且是水生环境中光合作用效率的一个主要促成因素。对变化条件的响应包括调节基因表达和蛋白质-蛋白质相互作用，这些作用有助于调整电子通量的利用以及控制光合电子传递（PET）的机制。在这方面，光系统I（PSI）反应中心的光化学活性可以支持循环电子流（CEF）和线性电子流（LEF）的平衡，以及氧化还原载体的偶联以供电子利用途径使用。因此，还原力利用的变化可能会导致PSI发生补偿性变化，以此作为支持电子通量平衡的一种手段。为了理解这种功能关系，我们研究了缺乏黄素二铁1催化的氧还原活性（ORR1）的细胞中PSI的特性及其光化学活性。在缺乏ORR1的情况下，氧气释放和消耗速率下降，同时PSI的寡聚形式向单体转变。在分离的PSI反应中心三聚体和单体组分中研究了这些变化对PSI能量和电子转移特性的影响。总体而言，结果表明在缺乏ORR1的情况下，PSI光化学通过与电子需求耗尽的协调而受到调节。
