Abstract
Plants and green algae optimize photosynthesis in changing light conditions by balancing the amount of light absorbed by photosystems I and II. These photosystems work in series to extract electrons from water and reduce NADP+ to NADPH. Light-harvesting complexes (LHCs) are held responsible for maintaining the balance by moving from one photosystem to the other in a process called state transitions. In the green alga Chlamydomonas reinhardtii, a photosynthetic model organism, state transitions are thought to involve 80% of the LHCs. Here, we demonstrate with picosecond-fluorescence spectroscopy on C. reinhardtii cells that, although LHCs indeed detach from photosystem II in state 2 conditions, only a fraction attaches to photosystem I. The detached antenna complexes become protected against photodamage via shortening of the excited-state lifetime. It is discussed how the transition from state 1 to state 2 can protect C. reinhardtii in high-light conditions and how this differs from the situation in plants.
Original language | English |
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Pages (from-to) | 3460-3465 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 111 |
Issue number | 9 |
DOIs | |
Publication status | Published - 2014 |
Keywords
- light-harvesting-complex
- excitation-energy transfer
- resolved chlorophyll fluorescence
- alga scenedesmus-obliquus
- protein-phosphorylation
- thylakoid membrane
- charge separation
- supramolecular organization
- arabidopsis-thaliana
- angstrom resolution