Light-driven Proton Pumps as a Potential Regulator for Carbon Fixation in Marine Diatoms
Date of Original Version
Diatoms are a major phytoplankton group responsible for approximately 20% of carbon fixation on Earth. They perform photosynthesis using light-harvesting chlorophylls located in plastids, an organelle obtained through eukaryote-eukaryote endosymbiosis. Microbial rhodopsin, a photoreceptor distinct from chlorophyll-based photosystems, was recently identified in some diatoms. However, the physiological function of diatom rhodopsin remains unclear. Heterologous expression techniques were herein used to investigate the protein function and subcellular localization of diatom rhodopsin. We demonstrated that diatom rhodopsin acts as a light-driven proton pump and localizes primarily to the outermost membrane of four membrane-bound complex plastids. Using model simulations, we also examined the effects of pH changes inside the plastid due to rhodopsin-mediated proton transport on photosynthesis. The results obtained suggested the involvement of rhodopsin-mediated local pH changes in a photosynthetic CO2-concentrating mechanism in rhodopsin-possessing diatoms.
Publication Title, e.g., Journal
Microbes and Environments
Yoshizawa, Susumu, Tomonori Azuma, Keiichi Kojima, Keisuke Inomura, Masumi Hasegawa, Yosuke Nishimura, Masuzu Kikuchi, Gabrielle Armin, Yuya Tsukamoto, Hideaki Miyashita, Kentaro Ifuku, Takashi Yamano, Adrian Marchetti, Hideya Fukuzawa, Yuki Sudo, and Ryoma Kamikawa. "Light-driven Proton Pumps as a Potential Regulator for Carbon Fixation in Marine Diatoms." Microbes and Environments 38, 2 (2023). doi: 10.1264/jsme2.ME23015.