Structural analysis of primitive red alga Galdieria sulphuraria photosystem I-light harvesting Complex

May 20, 2025

This structure of primitive red alga provides a framework for exploring evolutionary adaptation

A collaborative research group from Shizuoka University, Okayama University, Kyoto University, and the RIKEN CSRS has determined the structure of the photosystem I-light harvesting complex I (PSI-LHCI) from the primitive red alga Galdieria sulphuraria at a resolution of 2.19Å by cryo-EM single-particle analysis. This study provides a key framework for understanding the evolutionary adaptation of the photosynthetic apparatus in red algae and is expected to contribute to future progress in photosynthesis research.

Red algae are known to possess unique light-harvesting systems that differ from those of green plants and cyanobacteria. The structure of G. sulphuraria PSI reveals the absence of phylloquinone, which is normally present as a secondary electron acceptor in PSI, and the presence of a benzoquinone-like molecule instead. Furthermore, a phylogenetic analysis of the light-harvesting complex I (LHCI) subunits suggests that this alga has retained ancestral traits while undergoing adaptive evolution. These findings provide a valuable framework for understanding the molecular evolution of PSI-LHCI and how red algae have adapted their photosynthetic machinery to their unique habitats.

 

Original article

Science Advances doi: 10.1126/sciadv.adv7488

K. Kato, M. Kumazawa, Y. Nakajima, T. Suzuki, N. Dohmae, J.-R. Shen, K. Ifuku, R. Nagao,

"Structure of a photosystem I supercomplex from Galdieria sulphuraria close to an ancestral red alga".

Contact

Naoshi Dohmae
Unit Leader
Biomolecular Characterization Unit