PT  - JOURNAL ARTICLE
AU  - Susumu Yoshizawa
AU  - Tomonori Azuma
AU  - Keiichi Kojima
AU  - Keisuke Inomura
AU  - Masumi Hasegawa
AU  - Yosuke Nishimura
AU  - Masuzu Kikuchi
AU  - Gabrielle Armin
AU  - Hideaki Miyashita
AU  - Kentaro Ifuku
AU  - Takashi Yamano
AU  - Adrian Marchetti
AU  - Hideya Fukuzawa
AU  - Yuki Sudo
AU  - Ryoma Kamikawa
TI  - Proton-pumping rhodopsins in marine diatoms
AID  - 10.1101/2022.01.18.476826
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.01.18.476826
4099  - http://biorxiv.org/content/early/2022/01/20/2022.01.18.476826.short
4100  - http://biorxiv.org/content/early/2022/01/20/2022.01.18.476826.full
AB  - Diatoms are a major phytoplankton group responsible for about 20% of Earth’s primary production. They carry out photosynthesis inside the plastid, an organelle obtained through eukaryote-eukaryote endosymbiosis. Recently, microbial rhodopsin, a photoreceptor distinct from chlorophyll-based photosystems, has been identified in certain diatoms. However, the physiological function of diatom rhodopsin is not well understood. Here we show that the diatom rhodopsin acts as a light-driven proton pump and localizes to the outermost membrane of the four membrane-bound complex plastids. Heterologous expression techniques were used to investigate the protein function and subcellular localization of diatom rhodopsin. Using model simulations, we further evaluated the physiological role of the acidic pool in the plastid produced by proton-transporting rhodopsin. Our results propose that the rhodopsin-derived acidic pool may be involved in a photosynthetic CO2-concentrating mechanism and assist CO2 fixation in diatom cells.Competing Interest StatementThe authors have declared no competing interest.