Kinetics of excitation trapping in intact Photosystem I of Chlamydomonas reinhardtii and Arabidopsis thaliana

Ihalainen, Janne A.; Stokkum, Ivo H. M. van; Gibasiewicz, Krzysztof; Germano, M.; Grondelle, Rienk van; Dekker, Jan

doi:10.1016/j.bbabio.2004.11.007

Cited by 71 publications

(106 citation statements)

References 39 publications

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“…It is tempting to consider this loss channel to have the same origin as that found in the native PSI-LHCI particles. 12,52 The time constant for the loss channel from the Intermediate compartment is about 170 ps for the Lhca1/4 dimer. The Lhca1/4 dimer is considered to be a "natural" dimer in the PSI-LHCI particle.…”

Section: Discussionmentioning

confidence: 99%

“…On the basis of the target analysis of time-resolved fluorescence data, the "loss" channel in PSI-LHCI was modeled to be about 150 ps. 12 In principle, the above-mentioned structural rearrangement in the excited state can be very small (on the order of 0.1 Å), and it can be attributed to the formation of an excimer state. Such an excimer character was proposed previously to explain the emission properties of the red pigments.…”

Section: Discussionmentioning

confidence: 99%

“…The red-most states in the PSI antenna are even lower than the main absorption of the reaction center of PSI (700 nm). It has been shown that these red states prolong the overall trapping time of native PSI-LHCI particles in green plants 12,13 and in PSI core particles from cyanobacteria. 14,15 Because isolated LHCI preparations from green plants usually consist of two or three types of dimeric Lhca complexes, the spectroscopic studies on isolated LHCI have revealed information averaged over the Lhca proteins.…”

Section: Introductionmentioning

confidence: 99%

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Excitation Decay Pathways of Lhca Proteins: A Time-Resolved Fluorescence Study

et al. 2005

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Light-harvesting complex I (LHCI), which serves as a peripheral antenna for photosystem I (PSI) in green plants, consists mainly of four polypeptides, Lhca1-4. We report room temperature emission properties of individual reconstituted monomeric Lhca proteins (Lhca1, -2, -3, and -4) and dimeric Lhca1/4, performed by steady-state and time-resolved fluorescence techniques. The emission quantum yields of the samples are approximately 0.12, 0.085, 0.081, 0.041, and 0.063 for Lhca1, -2, -3, -4, and the -1/4 dimer, respectively, which is considerably lower than the value of 0.22 found for light-harvesting complex II (LHCII), the main peripheral antenna complex of photosystem II in green plants. The decay components of LHCI proteins can be divided in two categories: Lhca1 and Lhca3 have decay times of 1.1-1.6 ns and 3.3-3.6 ns, and Lhca2 and Lhca4 have decay times of 0.7-0.9 ns and 3.1-3.2 ns. These categories seem to correlate with the pigment composition of the samples. All decay times are faster than that observed previously for LHCII. When the absolute emission yields and the lifetimes of the Lhca samples are combined, the overall emission properties of the individual Lhca proteins are expressed in terms of their emitting dipole moment strength. In the samples without extreme red states, that is, Lhca1 and Lhca2, the emitting dipole moment has a value close to unity (relative to monomeric chlorophyll in acetone), which is similar to that for LHCII, whereas, in the samples with the red-most state (F-730), that is, Lhca3, -4, and the -1/4 dimer, the emitting dipole moment has a value less than unity (0.6-0.8), which can be explained by mixing the red-most (exciton) state with a dark charge-transfer state, as suggested in previous PSI red pigment studies. In addition, we find a lifetime component of ∼50-150 ps in all red-pigment-containing samples, which cannot be due to "slow" energy transfer, but is instead assigned to an unrelaxed state of the pigment-protein, which, on this time-scale, is converted into the final emitting state.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Excitation Decay Pathways of Lhca Proteins: A Time-Resolved Fluorescence Study

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“…Another possibility is that some CFL 250 ps in WT cells originates from the PSI associated with LHCII formed in state 2. This possibility can be excluded, however, because less than 2% of the fluorescence at 665-685 nm is derived from PSI at room temperature (13), and the CFL of PSI fluorescence at those wavelengths is shorter than ∼70 ps (18)(19)(20), a time range that our FLIM system cannot resolve. Taken together, these observations suggest that the CFL 250 ps observed in WT cells indicates phospho-LHCII dissociation, and that FLIM enabled visualization of the spatiotemporal spread of dissociated phospho-LHCII during state 2 transitions in live cells.…”

Section: Chlorophyll Fluorescence Lifetime Of Dissociated Phospho-lhcmentioning

confidence: 99%

Live-cell imaging of photosystem II antenna dissociation during state transitions

Iwai

Yokono²,

Inada³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

123

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Plants and green algae maintain efficient photosynthesis under changing light environments by adjusting their light-harvesting capacity. It has been suggested that energy redistribution is brought about by shuttling the light-harvesting antenna complex II (LHCII) between photosystem II (PSII) and photosystem I (PSI) (state transitions), but such molecular remodeling has never been demonstrated in vivo. Here, using chlorophyll fluorescence lifetime imaging microscopy, we visualized phospho-LHCII dissociation from PSII in live cells of the green alga Chlamydomonas reinhardtii. Induction of energy redistribution in wild-type cells led to an increase in, and spreading of, a 250-ps lifetime chlorophyll fluorescence component, which was not observed in the stt7 mutant incapable of state transitions. The 250-ps component was also the dominant component in a mutant containing the light-harvesting antenna complexes but no photosystems. The appearance of the 250-ps component was accompanied by activation of LHCII phosphorylation, supporting the visualization of phospho-LHCII dissociation. Possible implications of the unbound phospho-LHCII on energy dissipation are discussed.photosynthesis | fluorescence lifetime imaging microscopy | green algae | light-harvesting | energy dissipation I n the thylakoid membranes of chloroplasts, photosystems I and II (PSI and PSII) work in concert to carry out photosynthetic electron transfer from water to NADP + . For efficient photosynthesis under changing light conditions, balancing absorbed light energy between the two photosystems, or state transition, is important (1-3). The plastoquinone (PQ) pool, an intersystem electron carrier, monitors changes in light quality and quantity and activates a protein kinase for light-harvesting complex (LHC) II (3-5). LHCII phosphorylation leads to a decrease in PSII light absorption (6, 7), which occurs on a timescale of minutes without any changes in gene expression. The decrease is therefore considered to be due to the reorganization of the PSII antenna system, such as dissociation of phospho-LHCII from PSII.The fate of dissociated phospho-LHCII has been investigated in vitro. Subfractionation of phosphorylated thylakoid membranes showed that the stroma lamella (non-appressed) fraction, where PSI was predominantly located, contained more phospho-LHCII than the grana (appressed) fraction, where PSII was predominantly located (8-10). Isolation of PSII under PQ pool-oxidizing conditions provided the evidence that unphospho-LHCII remained bound to PSII, whereas under PQ pool-reducing conditions phospho-LHCII was dissociated from PSII (11). Isolation of PSI under the same conditions revealed that the dissociated LHCII (including both major and minor LHCII) were reassociated with PSI (12). Thus, state transitions are accompanied by LHCII relocation between the two photosystems.However, because such LHCII migrations have been observed only in vitro, it still remains to be uncovered what happens during the LHCII migration in vivo. Does LHCII really disso...

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“…4 are due to qE. We associate the remaining amplitude of the 70 ps component with PSI quenching (9,15,16), and we ascribe the remaining amplitude of the 330 ps component partially to PSI quenching and partly to detached, phosphorylated light-harvesting complex II (LHCII) trimers (17).…”

Section: Measurement Of Time-resolved Fluorescence Decays During Lightmentioning

confidence: 99%

Fluorescence lifetime snapshots reveal two rapidly reversible mechanisms of photoprotection in live cells of Chlamydomonas reinhardtii

Amarnath

Zaks

Park

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Photosynthetic organisms avoid photodamage to photosystem II (PSII) in variable light conditions via a suite of photoprotective mechanisms called nonphotochemical quenching (NPQ), in which excess absorbed light is dissipated harmlessly. To quantify the contributions of different quenching mechanisms to NPQ, we have devised a technique to measure the changes in chlorophyll fluorescence lifetime as photosynthetic organisms adapt to varying light conditions. We applied this technique to measure the fluorescence lifetimes responsible for the predominant, rapidly reversible component of NPQ, qE, in living cells of Chlamydomonas reinhardtii. Application of high light to dark-adapted cells of C. reinhardtii led to an increase in the amplitudes of 65 ps and 305 ps chlorophyll fluorescence lifetime components that was reversed after the high light was turned off. Removal of the pH gradient across the thylakoid membrane linked the changes in the amplitudes of the two components to qE quenching. The rise times of the amplitudes of the two components were significantly different, suggesting that the changes are due to two different qE mechanisms. We tentatively suggest that the changes in the 65 ps component are due to charge-transfer quenching in the minor light-harvesting complexes and that the changes in the 305 ps component are due to aggregated light-harvesting complex II trimers that have detached from PSII. We anticipate that this technique will be useful for resolving the various mechanisms of NPQ and for quantifying the timescales associated with these mechanisms.photosynthesis | in vivo spectroscopy | time-resolved fluorescence | feedback de-excitation | pH-dependent regulation

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Kinetics of excitation trapping in intact Photosystem I of Chlamydomonas reinhardtii and Arabidopsis thaliana

Cited by 71 publications

References 39 publications

Excitation Decay Pathways of Lhca Proteins: A Time-Resolved Fluorescence Study

Excitation Decay Pathways of Lhca Proteins: A Time-Resolved Fluorescence Study

Live-cell imaging of photosystem II antenna dissociation during state transitions

Fluorescence lifetime snapshots reveal two rapidly reversible mechanisms of photoprotection in live cells of Chlamydomonas reinhardtii

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