Photosystem Architecture and Dynamics in Oxygenic Photosynthesis

Oxygenic photosynthesis relies on two large multisubunit assemblies, photosystem II (PSII) and photosystem I (PSI), embedded within the thylakoid membrane. Each photosystem comprises a reaction centre core surrounded by light-harvesting antenna proteins that bind chlorophylls and carotenoids to capture solar energy. Assembly into supercomplexes enables rapid excitation energy transfer from peripheral pigments to the reaction centre, where charge separation drives electron transport. Structural diversity across cyanobacteria, algae and higher plants reflects adaptation to varying light environments, with modifications in subunit composition and pigment networks fine-tuning light capture and photoprotection. Dynamics of photosystem architecture include state transitions, in which phosphorylated antennae migrate between PSII and PSI to balance excitation, and conformational shifts in response to temperature, light intensity and electric fields. The organisation of photosystems within stacked grana and non-appressed stroma lamellae further influences energy distribution and electron flow. Understanding these structural and dynamic features is essential for improving crop performance under fluctuating conditions and for designing bio-inspired solar energy devices.

Research from Nature Portfolio

Recent studies have resolved the cryo-electron microscopy structure of a PSI–LHCI supercomplex from symbiotic dinoflagellates, revealing two previously unrecognised core subunits alongside a suite of peripheral antenna proteins. Extended termini and loop rearrangements facilitate tight docking of light-harvesting pigments, while computational analysis of excitation energy transfer uncovers specialised pigment networks optimised for symbiotic ecosystems. Foundational work has also identified stable megacomplexes that physically couple PSII and PSI in higher plants, demonstrating that direct energy transfer between reaction centres contributes to photoprotection. These assemblies form and dissociate in response to light conditions, allowing PSII to divert excess excitation to PSI when its reaction centres are closed, thereby mitigating photodamage.

Photosystem Architecture and Dynamics in Oxygenic Photosynthesis publication trend

The graph below shows the total number of articles in photosystem architecture and dynamics in oxygenic photosynthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Photosystem I (PSI): A multi-subunit protein complex that performs light-driven electron transfer to produce reducing power.

Photosystem II (PSII): The membrane-embedded complex that oxidises water to release oxygen and electrons.

Light-harvesting complex I (LHCI): Peripheral antenna proteins associated with PSI that bind pigments to collect light energy.

Supercomplex: A stable assembly of core photosystem subunits with associated antenna proteins and cofactors.

Excitation energy transfer: The movement of excitation energy between pigments, directing it to the reaction centre.

Cryo-electron microscopy: A structural technique that images biological complexes at near-atomic resolution under cryogenic conditions.

References

1. Architecture of symbiotic dinoflagellate photosystem I–light-harvesting supercomplex in Symbiodinium. Nature Communications (2024).
2. Stimuli‐Induced Subconformation Transformation of the PSI‐LHCI Protein at Single‐Molecule Resolution. Advanced Science (2023).
3. Structural basis and evolution of the photosystem I–light-harvesting supercomplex of cryptophyte algae. The Plant Cell (2023).
4. The structure of plant photosystem I super-complex at 2.8 Å resolution. eLife (2015).
5. Thylakoid Protein Phosphorylation in Higher Plant Chloroplasts Optimizes Electron Transfer under Fluctuating Light. Plant Physiology (2009).
6. A megacomplex composed of both photosystem reaction centres in higher plants. Nature Communications (2015).
7. Three-Dimensional Architecture of Grana and Stroma Thylakoids of Higher Plants as Determined by Electron Tomography. Plant Physiology (2011).