In photosynthetic organisms, the photosystem I-light-harvesting complex, responsible for converting light energy into chemical energy during photosynthesis, exhibits significant structural and size variations reflecting adaptations to diverse light environments. This diversification has undergone profound evolution, particularly during the transition from coastal zones toward both terrestrial and marine environments.
Coccolithophores originated in ancient coastal zones, conquered the open ocean during the Mesozoic era, and reached their peak prosperity, holding significant implications for contemporary global climate and ecology. Emiliania huxleyi, the most renowned model organism within the coccolithophores group, is also a crucial subject of study in coastal biology.
On September 11, Dr. Wang Yin-chu from Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, in collaboration with the research team of Professor Wang Wenda from the Institute of Botany, Chinese Academy of Sciences, published a cover paper titled “Structure and function of a huge photosystem I-fucoxanthin chlorophyll supercomplex from a coccolithophore” in the top international academic journal Science (Figure 1). Wang Yin-chu from the Yantai Institute of Coastal Zone Research is the co-first author of the paper.
Figure 1. Science cover featuring the PSI-FCPI super-complex model of the coccolithophore Emiliania huxleyi
This study report a structure of a PSI-fucoxanthin chlorophyll a/c binding protein (FCPI) supercomplex from a coccolithophore Emiliania huxleyi (Eh) at 2.79 Å resolution by cryo-EM, which showed a huge Eh-PSI-FCPI supercomplex containing 38 peripheral Eh-FCPI antennae and a linker-protein (EhLP) in addition to the PSI core. A total of 819-pigment network was found in Eh-PSI-FCPI, which function to capture and transfer the light energy with a 95% quantum efficiency. This elucidates how its modular Eh-FCPI arrangement contributes to the expansion of PSI cross-section and efficient light harvesting. This study reveals for the first time at the atomic level the unique strategy employed by coccolithophores to adapt to marine light environments by expanding and optimizing its photosystem architecture, marking a major discovery in the evolution of light adaptation in photosynthetic organisms (Figure 2).
Figure 2. Structural relationship of PSI-LHCs from typical photosynthetic species based on subunit arrangement.
Dr. Wang Yinchu is dedicated to database-driven research on the evolution of coastal plant resources. The China Coastal Plant Resource Database he established was successfully selected for inclusion in the National Basic Science Data Center in 2021, establishing coastal science as a recognized foundational discipline. In advancing the discipline development alongside the database, this research completes the third part of the tetralogical story of coastal zone organisms: “1) Origin, 2) Landing, 3) Ocean Conquest, and 4) Coexistence.”
Article link: https://doi.org/10.1126/science.adv2132
