Light-harvesting complexes access analogue emissive states in different environments

Area of Science:

• Photosynthesis research
• Plant molecular biology
• Biophysics

Background:

• Light-harvesting complexes (LHCs) in plants modulate excitation levels under fluctuating light.
• LHCs switch between functional states with distinct fluorescence properties for regulation.
• Isolated LHCs are highly fluorescent, while aggregates show fluorescence quenching, crucial for photoprotection.

Purpose of the Study:

• Investigate how the conformational landscape of LHCs is modulated in different environments.
• Clarify the role of aggregation in the photoprotective state of LHCs.
• Analyze the heterogeneity of emissive states in CP29 aggregates.

Main Methods:

• Time-resolved fluorescence experiments on CP29 aggregates.
• Comparison with data from isolated CP29.
• Study of mutants lacking specific chlorophylls.

Main Results:

• Aggregation stabilizes short-lived conformations but primarily enhances quenching via energetic connectivity.
• Dissipative states, accessed in isolated forms, are maintained in aggregates.
• Far-red emission enhancement in oligomers is due to long-lived redshifted complexes competing with quenched complexes.

Conclusions:

• Protein aggregation in LHCs is not the sole trigger for photoprotection; energetic connectivity plays a key role.
• Specific chlorophylls significantly influence the conformational landscape of LHCs.
• Understanding LHC conformational dynamics is vital for comprehending plant photoprotection strategies.