Abstract
Photosynthetic activity and respiration share the thylakoid membrane in cyanobacteria. We present a series of spectrally resolved fluorescence experiments where whole cells of the cyanobacterium Synechocystis sp. PCC 6803 and mutants thereof underwent a dark-to-light transition after different dark-adaptation (DA) periods. Two mutants were used: (i) a PSI-lacking mutant (ΔPSI) and (ii) M55, a mutant without NAD(P)H dehydrogenase type-1 (NDH-1). For comparison, measurements of the wild-type were also carried out. We recorded spectrally resolved fluorescence traces over several minutes with 100 ms time resolution. The excitation light was at 590 nm so as to specifically excite the phycobilisomes. In ΔPSI, DA time has no influence, and in dichlorophenyl-dimethylurea (DCMU)-treated samples we identify three main fluorescent components: PB–PSII complexes with closed (saturated) RCs, a quenched or open PB–PSII complex, and a PB–PSII ‘not fully closed.’ For the PSI-containing organisms without DCMU, we conclude that mainly three species contribute to the signal: a PB–PSII–PSI megacomplex with closed PSII RCs and (i) slow PB → PSI energy transfer, or (ii) fast PB → PSI energy transfer and (iii) complexes with open (photochemically quenched) PSII RCs. Furthermore, their time profiles reveal an adaptive response that we identify as a state transition. Our results suggest that deceleration of the PB → PSI energy transfer rate is the molecular mechanism underlying a state 2 to state 1 transition.
| Original language | English |
|---|---|
| Pages (from-to) | 307–320 |
| Number of pages | 14 |
| Journal | Photosynthesis Research |
| Volume | 137 |
| Issue number | 2 |
| Early online date | 29 Mar 2018 |
| DOIs | |
| Publication status | Published - Aug 2018 |
Funding
Acknowledgements AMA gratefully acknowledges Michael Reus for his assistance in re-building the multiple LED set-up in Amsterdam and Joris Snellenburg for his valuable assistance during the automation of the data acquisition as well as helpful discussions. Roberta Croce and Alfred Holzwarth are thanked for letting us use this set-up. The ΔPSI mutant which was originally constructed by Wim Vermaas (Arizona State University, Tempe, Arizona, U.S.) was kindly provided to us by Christiane Funk (Umeå University, Sweden). M55 was kindly provided by Teruo Ogawa (Nagoya University, Japan). This research was performed as part of the BioSolar Cells research program, sponsored by the Dutch Ministry of Economic Affairs. This work is part of the research program of the Netherlands Organization for Scientific Research (NWO, previously FOM). AMA gratefully acknowledges Michael Reus for his assistance in re-building the multiple LED set-up in Amsterdam and Joris Snellenburg for his valuable assistance during the automation of the data acquisition as well as helpful discussions. Roberta Croce and Alfred Holzwarth are thanked for letting us use this set-up. The ΔPSI mutant which was originally constructed by Wim Vermaas (Arizona State University, Tempe, Arizona, U.S.) was kindly provided to us by Christiane Funk (Umeå University, Sweden). M55 was kindly provided by Teruo Ogawa (Nagoya University, Japan). This research was performed as part of the BioSolar Cells research program, sponsored by the Dutch Ministry of Economic Affairs. This work is part of the research program of the Netherlands Organization for Scientific Research (NWO, previously FOM). Alonso M. Acuña and Pascal van Alphen have contributed equally to this work.
| Funders | Funder number |
|---|---|
| Ministerie van Economische Zaken | |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | |
| Nagoya University | |
| Umeå Universitet |
Keywords
- Cyanobacteria
- Cyclic electron flow
- Plastoquinone pool
- Singular value decomposition
- Spectrally resolved fluorometry
- Time-resolved spectroscopy