Plastocyanin affects photosynthesis and high light acclimation by modulating redox states of electron transport chain in Chlamydomonas reinhardtii
Guangxi Wu, Song Bin, Jun Chen, Jun Li, Heng Yi, Chuyi Wei, Huiqi Zheng, Chen Chen, Byeong‐ha Lee, Xiaoxiong Wang, Wenqiang Yang, Zhangli Hu, Xiaozheng Li
Abstract
The role of plastocyanin in regulating photosynthetic and high light response remains unclear. Here we found that a larger PC pool effectively increased the linear electron flow while lowering the reduction state of plastoquinone (PQ) and ferredoxin (Fd), subsequently decreasing ROS formation. The biomass yield was increased in PC-rich cells, which, along with a decrease in intracellular starch content, up-regulated the RuBisCO activity, thereby enhancing carbon fixation. Meanwhile, we observed that ADP-glucose pyrophosphorylase activity was down-regulated, probably due to a lower Fd reduction state leading to reduced starch synthesis. During the transition from low to high light, PC accumulates to a substantial level, effectively reducing the reduction state of PQ and restoring Fv/Fm. These findings highlight the critical function of PC as a redox capacitor in affecting PET, CO2 fixation, and high light acclimation by modulating the redox states of the electron transport chain (ETC) and its potential for optimizing photosynthetic processes. In-depth studies using Chlamydomonas reinhardtii with different plastocyanin (PC) pool sizes reveal that PC acts as a redox capacitor, optimizing photosynthetic electron transport, CO2 fixation, and high light tolerance, and offers potential strategies for improving photosynthetic efficiency.