Insights into the phylogenetic, structural and functional evolution of LHC superfamily in photosynthetic organisms

Photosynthesis is the fundamental process for the survival of photosynthetic organisms. The light-harvesting complexes (LHCs) play a crucial role in light energy capture and transfer. Despite their conserved role in energy transfer, the evolutionary basis for functional diversification of LHCs across photosynthetic lineages remains largely unclear. In this study, we performed phylogenetic analyses based on 65 genomes covering all major linages of photosynthetic organisms and identified 1922 LHC proteins, which were classified into four groups: LHCA, LHCB, LHC-like, and FCP. The LHC gene family has undergone dynamic diversification through lineage-specific mechanisms in which green algae primarily utilized dispersed duplications, while land plants increasingly relied on whole-genome duplications (WGDs). Structural analyses revealed key adaptive modifications: PSI-LHCI transitioned from a double-layer crescent antenna in green algae to a simplified single-layer configuration in land plants, while PSII-LHCII in angiosperms replaced the N-LHCII trimer with CP24 to optimize light harvesting. Expression profiling revealed the functional diversification of different LHC members, with LHCA/LHCB members showing constitutive expression in photosynthetic tissues and strong induction of abiotic stresses, while LHC-like exhibited specialized responses to specific environmental challenges. Our study enhances better understanding of the evolutionary scenario of LHC superfamily during the evolution of photosynthetic organisms, and provides a foundation for future research on the molecular mechanisms underlying the adaptation of LHCs to extreme environments.