Photosystem II Biogenesis and Repair Mechanisms in Photosynthetic Organisms

Photosystem II (PSII) is a multi‐subunit pigment–protein complex embedded in the thylakoid membrane that drives water oxidation and oxygen evolution, forming the foundation of oxygenic photosynthesis. Its biogenesis follows a highly orchestrated sequence of events: co‐translational insertion of the D1 reaction centre subunit, sequential association of core proteins D2, CP43 and CP47, and integration of extrinsic oxygen‐evolving complex proteins. A suite of conserved auxiliary assembly factors guides the formation of early assembly intermediates such as the RC47 complex and stabilises nascent subunits. PSII is prone to photodamage, particularly to the D1 polypeptide under high‐light stress, triggering the PSII repair cycle. This repair entails selective degradation of damaged D1, transient disassembly of the PSII complex, re‐insertion of a newly synthesised D1, reassembly of the supercomplex and reactivation of water‐splitting activity. Repair also relies on specialised factors that facilitate disulfide bond rearrangement, subunit exchange and protection against reactive oxygen species. A deep understanding of these processes is crucial for improving photosynthetic efficiency, engineering stress tolerance in crops and designing artificial light‐harvesting devices.

Research from Nature Portfolio

Recent structural analysis of a PSII repair intermediate from a model green alga has captured an early stage of the repair cycle, revealing a complex containing three dedicated repair factors. These proteins appear to mediate the release of the manganese‐stabilising PsbO subunit, disassembly of peripheral antenna complexes and blockage of the quinone site to prevent premature electron transfer. The structure also reveals an α‐tocopherol quinone molecule adjacent to cytochrome b559, suggesting a novel photoprotective role in quenching reactive oxygen species during repair.

Photosystem II Biogenesis and Repair Mechanisms in Photosynthetic Organisms publication trend

The graph below shows the total number of articles in photosystem ii biogenesis and repair mechanisms in photosynthetic organisms across all publications each year (not limited to Nature Index journals).

Technical terms

Photosystem II (PSII): A membrane‐bound protein complex that catalyses light‐driven water oxidation and oxygen evolution in photosynthesis.

D1 protein: The core reaction centre subunit of PSII that binds key cofactors for charge separation and is frequently damaged under high light.

RC47 intermediate: A PSII assembly intermediate comprising the reaction centre core (D1–D2) associated with the CP47 antenna protein.

Photoinhibition: Light‐induced damage to PSII, primarily affecting the D1 protein, necessitating repair and replacement processes.

References

1. Co-translational Assembly of the D1 Protein into Photosystem II*. Journal of Biological Chemistry (1999).
2. Structural basis for an early stage of the photosystem II repair cycle in Chlamydomonas reinhardtii. Nature Communications (2024).
3. Eukaryote-specific assembly factor DEAP2 mediates an early step of photosystem II assembly in Arabidopsis. Plant Physiology (2023).
4. The Cyanobacterial Homologue of HCF136/YCF48 Is a Component of an Early Photosystem II Assembly Complex and Is Important for Both the Efficient Assembly and Repair of Photosystem II in Synechocystis sp. PCC 6803*. Journal of Biological Chemistry (2008).