Control of the maximal chlorophyll fluorescence yield by the Q&lt;sub&gt;B&lt;/sub&gt; binding site

Prášil, Ondřej; Kolber, Zbigniew; Falkowski, Paul G.

doi:10.1007/s11099-018-0768-x

Cited by 27 publications

(7 citation statements)

References 75 publications

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“…This value at room temperature and at 5°C varied from batch to batch between about 45 and 60% and about 35 and 45%, respectively; the F v /F m parameter under the same conditions was 0.845 ± 0.035 (n = 9, obtained from five different batches; data not shown). These observations are in good agreement with the data reported earlier on PSII CC by Magyar et al () and in reasonable accordance with observations on thylakoid membranes (Joliot and Joliot , Prášil et al ). By using a second STSF, the fluorescence level could be further raised, by about another 15% – but only after a sufficiently long Δt waiting time between the two flashes, and further excitations were required to reach the maximum level F m ; here MTSF excitation was used (the second MTSF laser pulse was applied to confirm that F m was reached).…”

Section: Resultssupporting

confidence: 93%

“…It has also been shown, in accordance with earlier literature data obtained on isolated thylakoid membranes (Joliot and Joliot 1979), that only the first STSF leads to stable charge separation (Q A reduction) and the F 1 -to-F 2 and the further fluorescence yield increments are given rise to by different physical mechanisms. Recently, Prášil et al (2018) have shown that variations in the fluorescence yield depend on the occupancy of the Q B binding site and on the capacity of the secondary electron acceptors to re-oxidize the reduced Q A . However, under our experimental conditions, significant participation of Q B could be ruled out (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Redox transients of P680 associated with the incremental chlorophyll‐a fluorescence yield rises elicited by a series of saturating flashes in diuron‐treated photosystem II core complex of Thermosynechococcus vulcanus

Sipka

Müller

Brettel

et al. 2019

Physiologia Plantarum

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Recent chlorophyll‐a fluorescence yield measurements, using single‐turnover saturating flashes (STSFs), have revealed the involvement of a rate‐limiting step in the reactions following the charge separation induced by the first flash. As also shown here, in diuron‐inhibited PSII core complexes isolated from Thermosynechococcus vulcanus the fluorescence maximum could only be reached by a train of STSFs. In order to elucidate the origin of the fluorescence yield increments in STSF series, we performed transient absorption measurements at 819 nm, reflecting the photooxidation and re‐reduction kinetics of the primary electron donor P680. Upon single flash excitation of the dark‐adapted sample, the decay kinetics could be described with lifetimes of 17 ns (∼50%) and 167 ns (∼30%), and a longer‐lived component (∼20%). This kinetics are attributed to re‐reduction of P680•+ by the donor side of PSII. In contrast, upon second‐flash (with Δt between 5 μs and 100 ms) or repetitive excitation, the 819 nm absorption changes decayed with lifetimes of about 2 ns (∼60%) and 10 ns (∼30%), attributed to recombination of the primary radical pair P680•+Pheo•–, and a small longer‐lived component (∼10%). These data confirm that only the first STSF is capable of generating stable charge separation – leading to the reduction of QA; and thus, the fluorescence yield increments elicited by the consecutive flashes must have a different physical origin. Our double‐flash experiments indicate that the rate‐limiting steps, detected by chlorophyll‐a fluorescence, are not correlated with the turnover of P680.

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Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Redox transients of P680 associated with the incremental chlorophyll‐a fluorescence yield rises elicited by a series of saturating flashes in diuron‐treated photosystem II core complex of Thermosynechococcus vulcanus

Sipka

Müller

Brettel

et al. 2019

Physiologia Plantarum

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“…While the original discovery of photochemical and thermal components was made more than 50 years ago (Morin 1964 ; Delosme 1967 ), still no general consensus has been reached on the interpretation of the thermal phase (for a variety of different views, see e.g. Lazar 2006 ; Schansker et al 2011 ; Stirbet and Govindjee 2012 ; Prasil et al 2018 ; Laisk and Oja 2020 ). On the other hand, it is generally accepted that the O - I 1 rise specifically reflects the closure of PS II reaction centers and, hence, may be considered to reflect photosystem II emission, F (II), only.…”

Section: Introductionmentioning

confidence: 99%

Evidence for variable chlorophyll fluorescence of photosystem I in vivo

Schreiber

Klughammer

2021

Photosynth Res

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Room temperature fluorescence in vivo and its light-induced changes are dominated by chlorophyll a fluorescence excited in photosystem II, F(II), peaking around 685 nm. Photosystem I fluorescence, F(I), peaking around 730 nm, so far has been assumed to be constant in vivo. Here, we present evidence for significant contributions of F(I) to variable fluorescence in the green unicellular alga Chlorella vulgaris, the cyanobacterium Synechococcus leopoliensis and a light-green ivy leaf. A Multi-Color-PAM fluorometer was applied for measurements of the polyphasic fluorescence rise (O-I1-I2-P) induced by strong 440 nm light in a dilute suspension of Chlorella, with detection alternating between emission above 700 nm (F > 700) and below 710 nm (F < 710). By averaging 10 curves each of the F > 700 and F < 710 recordings even small differences could be reliably evaluated. After equalizing the amplitudes of the O-I1 phase, which constitutes a specific F(II) response, the O-I1-I2 parts of the two recordings were close to identical, whereas the I2-P phase was larger in F > 700 than in F < 710 by a factor of 1.42. In analogous measurements with Synechococcus carried out in the dark state 2 using strong 625 nm actinic light, after O-I1 equalization the I2-P phase in F > 700 exceeded that in F < 710 even by a factor of 1.99. In measurements with Chlorella, the I2-P phase and with it the apparent variable fluorescence of PS I, Fv(I), were suppressed by moderate actinic background light and by the plastoquinone antagonist DBMIB. Analogous measurements with leaves are rendered problematic by unavoidable light intensity gradients and the resulting heterogenic origins of F > 700 and F < 710. However, a light-green young ivy leaf gave qualitatively similar results as those obtained with the suspensions, thus strongly suggesting the existence of Fv(I) also in leaves.

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“…In the first stage of the assay to test the system, an exogenous electron acceptor, DMBQ, is introduced to the membranes at a relatively high concentration, to replace the natural electron carriers (PQ) which are likely to be saturated. [ 31 ] If DMBQ successfully accepts electrons from PSII, the level of Chl fluorescence should be reduced in its presence compared to its absence, because excitation energy can be used to eject electrons rather than being reemitted. In the final stage of the assay, “hydroxylamine” can be added as an aqueous solution and is known to increase the Chl fluorescence again (Figure 6a).…”

Section: Resultsmentioning

confidence: 99%

Model Lipid Membranes Assembled from Natural Plant Thylakoids into 2D Microarray Patterns as a Platform to Assess the Organization and Photophysics of Light‐Harvesting Proteins

Meredith

Yoneda

Hancock

et al. 2021

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Natural photosynthetic “thylakoid” membranes found in green plants contain a large network of light‐harvesting (LH) protein complexes. Rearrangement of this photosynthetic machinery, laterally within stacked membranes called “grana”, alters protein–protein interactions leading to changes in the energy balance within the system. Preparation of an experimentally accessible model system that allows the detailed investigation of these complex interactions can be achieved by interfacing thylakoid membranes and synthetic lipids into a template comprised of polymerized lipids in a 2D microarray pattern on glass surfaces. This paper uses this system to interrogate the behavior of LH proteins at the micro‐ and nanoscale and assesses the efficacy of this model. A combination of fluorescence lifetime imaging and atomic force microscopy reveals the differences in photophysical state and lateral organization between native thylakoid and hybrid membranes, the mechanism of LH protein incorporation into the developing hybrid membranes, and the nanoscale structure of the system. The resulting model system within each corral is a high‐quality supported lipid bilayer that incorporates laterally mobile LH proteins. Photosynthetic activity is assessed in the hybrid membranes versus proteoliposomes, revealing that commonly used photochemical assays to test the electron transfer activity of photosystem II may actually produce false‐positive results.

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Control of the maximal chlorophyll fluorescence yield by the Q<sub>B</sub> binding site

Cited by 27 publications

References 75 publications

Redox transients of P680 associated with the incremental chlorophyll‐a fluorescence yield rises elicited by a series of saturating flashes in diuron‐treated photosystem II core complex of Thermosynechococcus vulcanus

Redox transients of P680 associated with the incremental chlorophyll‐a fluorescence yield rises elicited by a series of saturating flashes in diuron‐treated photosystem II core complex of Thermosynechococcus vulcanus

Evidence for variable chlorophyll fluorescence of photosystem I in vivo

Model Lipid Membranes Assembled from Natural Plant Thylakoids into 2D Microarray Patterns as a Platform to Assess the Organization and Photophysics of Light‐Harvesting Proteins

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