Abstract
Sunlight drives photosynthesis but can also cause photodamage. To protect themselves, photosynthetic organisms dissipate the excess absorbed energy as heat, in a process known as nonphotochemical quenching (NPQ). In green algae, diatoms, and mosses, NPQ depends on the light-harvesting complex stress-related (LHCSR) proteins. Here we investigated NPQ in Chlamydomonas reinhardtii using an approach that maintains the cells in a stable quenched state. We show that in the presence of LHCSR3, all of the photosystem (PS) II complexes are quenched and the LHCs are the site of quenching, which occurs at a rate of ∼150 ps −1 and is not induced by LHCII aggregation. The effective light-harvesting capacity of PSII decreases upon NPQ, and the NPQ rate is independent of the redox state of the reaction center. Finally, we could measure the pH dependence of NPQ, showing that the luminal pH is always above 5.5 in vivo and highlighting the role of LHCSR3 as an ultrasensitive pH sensor.
| Original language | English |
|---|---|
| Pages (from-to) | 8320-8325 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 116 |
| Issue number | 17 |
| Early online date | 8 Apr 2019 |
| DOIs | |
| Publication status | Published - 23 Apr 2019 |
Funding
We thank Jean-David Rochaix (University of Geneva) for providing the stt7-9 mutant, Giovanni Finazzi (CEA Grenoble) for the npq4/stt7-9 double mutant, Stefano Caffarri (Université Aix-Marseille) for the PsbS antibodies, Bart van Oort (VU Amsterdam) for critically reading the manuscript, Lauren Nicol (VU Amsterdam) for the isolated thylakoid membrane of Arabidopsis, and Tom van den Berg (VU Amsterdam) for assistance in the HPLC experiment. W.J.N. was supported by a European Commission Marie Curie Actions Individual Fellowship (799083). This work was supported by the European Research Council via an ERC consolidator grant (214113 to R.C.) and by the Dutch Organization for Scientific Research (NWO) via a Vici grant (to R.C.). the PsbS antibodies, Bart van Oort (VU Amsterdam) for critically reading the manuscript, Lauren Nicol (VU Amsterdam) for the isolated thylakoid membrane of Arabidopsis, and Tom van den Berg (VU Amsterdam) for assistance in the HPLC experiment. W.J.N. was supported by a European Commission Marie Curie Actions Individual Fellowship (799083). This work was supported by the European Research Council via an ERC consolidator grant (214113 to R.C.) and by the Dutch Organization for Scientific Research (NWO) via a Vici grant (to R.C.).
| Funders | Funder number |
|---|---|
| Dutch Organization for Scientific Research | |
| European Commission Marie Curie Actions | |
| Horizon 2020 Framework Programme | 799083 |
| European Research Council | 214113 |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | |
| Université de Genève |
Keywords
- Fluorescence
- Low pH
- Photosynthesis
- Photosystem II
- Ultrafast spectroscopy
