scholarly journals Trivial Excitation Energy Transfer to Carotenoids Is an Unlikely Mechanism for Non-photochemical Quenching in LHCII

2022 ◽  
Vol 12 ◽  
Author(s):  
Callum Gray ◽  
Tiejun Wei ◽  
Tomáš Polívka ◽  
Vangelis Daskalakis ◽  
Christopher D. P. Duffy
Keyword(s):  
Energy Transfer ◽  
Oscillator Strength ◽  
Quantum Chemical ◽  
Higher Plants ◽  
Photochemical Quenching ◽  
Relaxation Dynamics ◽  
Free Energy Surface ◽  
Range Interaction ◽  
Linear Absorption ◽  
Non Photochemical Quenching

Higher plants defend themselves from bursts of intense light via the mechanism of Non-Photochemical Quenching (NPQ). It involves the Photosystem II (PSII) antenna protein (LHCII) adopting a conformation that favors excitation quenching. In recent years several structural models have suggested that quenching proceeds via energy transfer to the optically forbidden and short-lived S1 states of a carotenoid. It was proposed that this pathway was controlled by subtle changes in the relative orientation of a small number of pigments. However, quantum chemical calculations of S1 properties are not trivial and therefore its energy, oscillator strength and lifetime are treated as rather loose parameters. Moreover, the models were based either on a single LHCII crystal structure or Molecular Dynamics (MD) trajectories about a single minimum. Here we try and address these limitations by parameterizing the vibronic structure and relaxation dynamics of lutein in terms of observable quantities, namely its linear absorption (LA), transient absorption (TA) and two-photon excitation (TPE) spectra. We also analyze a number of minima taken from an exhaustive meta-dynamical search of the LHCII free energy surface. We show that trivial, Coulomb-mediated energy transfer to S1 is an unlikely quenching mechanism, with pigment movements insufficiently pronounced to switch the system between quenched and unquenched states. Modulation of S1 energy level as a quenching switch is similarly unlikely. Moreover, the quenching predicted by previous models is possibly an artifact of quantum chemical over-estimation of S1 oscillator strength and the real mechanism likely involves short-range interaction and/or non-trivial inter-molecular states.

scholarly journals Trivial Excitation Energy Transfer to Carotenoids is an Unlikely Mechanism for Non-Photochemical Quenching in LHCII

2021 ◽  
Author(s):  
Callum Gray ◽  
Tiejun Wei ◽  
Tomáš Polívka ◽  
Vangelis Daskalakis ◽  
Christopher D. P. Duffy
Keyword(s):  
Energy Transfer ◽  
Oscillator Strength ◽  
Quantum Chemical ◽  
Transient Absorption ◽  
Higher Plants ◽  
Excitation Energy Transfer ◽  
Photochemical Quenching ◽  
Relaxation Dynamics ◽  
Linear Absorption ◽  
Non Photochemical Quenching

Higher plants defend themselves from bursts of intense light via the mechanism of Non-Photochemical Quenching (NPQ). It involves the Photosystem II (PSII) antenna protein (LHCII) adopting a conformation that favours excitation quenching. In recent years several structural models have suggested that quenching proceeds via energy transfer to the optically forbidden and short-lived S1 states of a carotenoid. It was proposed that this pathway was controlled by subtle changes in the relative orientation of a small number of pigments. However, quantum chemical calculations of S1 properties are not trivial and therefore its energy, oscillator strength and lifetime are treated as rather loose parameters. Moreover, the models were based either on a single LHCII crystal structure or Molecular Dynamics (MD trajectories) about a single minimum. Here we try and address these limitations by parameterizing the vibronic structure and relaxation dynamics of lutein in terms of observable quantities, namely linear absorption (LA) transient absorption (TA) and two-photon excitation (TPE) spectra. We also analyze a number of minima taken from an exhaustive meta-dynamical search of the LHCII potential energy surface. We show that trivial, Coulomb-mediated energy transfer to S1 is an unlikely quenching mechanism. Pigment movements are insufficient to switch the system between quenched and unquenched states. Modulation of S1 energy level as a quenching switch is similarly unlikely. Moreover, the quenching predicted by previous models is likely an artefact of quantum chemical over-estimation of S1 oscillator strength and the real mechanism likely involves non-trivial inter-molecular states.

Operation and regulation of the lutein epoxide cycle in seedlings of Ocotea foetens

2010 ◽  
Vol 37 (9) ◽  
pp. 859 ◽  
Author(s):  
Raquel Esteban ◽  
Shizue Matsubara ◽  
María Soledad Jiménez ◽  
Domingo Morales ◽  
Patricia Brito ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Higher Plants ◽  
Daily Basis ◽  
Field Conditions ◽  
Photochemical Quenching ◽  
Complete Restoration ◽  
Non Photochemical Quenching ◽  
First Time

Two xanthophyll cycles are present in higher plants: the ubiquitous violaxanthin (V) cycle and the taxonomically restricted lutein epoxide (Lx) cycle. Conversions of V to zeaxanthin (Z) in the first and Lx to lutein (L) in the second happen in parallel under illumination. Unlike the V cycle, in which full epoxidation is completed overnight, in the Lx cycle, this reaction has been described as irreversible on a daily basis in most species (the ‘truncated’ Lx cycle). However, there are some species that display complete restoration of Lx overnight (‘true’ Lx cycle). So far, little is known about the physiological meaning of these two versions of the Lx cycle. Therefore, in the present work, the ‘true’ Lx cycle operation was studied in seedlings of Ocotea foetens (Aiton) Benth. under controlled and field conditions. Complete overnight recovery of the Lx pool in the presence of norfluorazon suggested that the inter-conversions between Lx and L represent a true cycle in this species. Furthermore, Lx responded dynamically to environmental conditions during long-term acclimation. Our data demonstrate the operation of a ‘true’ Lx cycle and, for the first time, its potential involvement in the regulation of non-photochemical quenching in situ. We propose dual regulation of Lx cycle in O. foetens, in which the extent of Lx restoration depends on the intensity and duration of illumination.

scholarly journals Antenna Protein Clustering In Vitro Unveiled by Fluorescence Correlation Spectroscopy

2021 ◽  
Vol 22 (6) ◽  
pp. 2969
Author(s):  
Aurélie Crepin ◽  
Edel Cunill-Semanat ◽  
Eliška Kuthanová Trsková ◽  
Erica Belgio ◽  
Radek Kaňa
Keyword(s):  
Fluorescence Correlation Spectroscopy ◽  
Higher Plants ◽  
Fluorescence Emission ◽  
Correlation Spectroscopy ◽  
Photochemical Quenching ◽  
High Ph ◽  
Fluorescence Correlation ◽  
Non Photochemical Quenching

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.

Role of electron-transfer quenching of chlorophyll fluorescence by carotenoids in non-photochemical quenching of green plants

2005 ◽  
Vol 33 (4) ◽  
pp. 858-862 ◽  
Author(s):  
A. Dreuw ◽  
G.R. Fleming ◽  
M. Head-Gordon
Keyword(s):  
Electron Transfer ◽  
Chlorophyll Fluorescence ◽  
Charge Transfer ◽  
Excited States ◽  
Quantum Chemical ◽  
Photochemical Quenching ◽  
Quenching Mechanism ◽  
High Level ◽  
Non Photochemical Quenching

NPQ (non-photochemical quenching) is a fundamental photosynthetic mechanism by which plants protect themselves against excess excitation energy and the resulting photodamage. A discussed molecular mechanism of the so-called feedback de-excitation component (qE) of NPQ involves the formation of a quenching complex. Recently, we have studied the influence of formation of a zeaxanthin–chlorophyll complex on the excited states of the pigments using high-level quantum chemical methodology. In the case of complex formation, electron-transfer quenching of chlorophyll-excited states by carotenoids is a relevant quenching mechanism. Furthermore, additionally occurring charge-transfer excited states can be exploited experimentally to prove the existence of the quenching complex during NPQ.

scholarly journals Fibrillin 2 interacts with other proteins to protect photosystem II against abiotic stress in Arabidopsis thaliana

2020 ◽  
Author(s):  
Diego Torres-Romero ◽  
Ángeles Gómez-Zambrano ◽  
Antonio Jesús Serrato ◽  
Mariam Sahrawy ◽  
Ángel Mérida
Keyword(s):  
Abiotic Stress ◽  
Photosystem Ii ◽  
Higher Plants ◽  
Photochemical Quenching ◽  
Allene Oxide ◽  
Effective Quantum Yield ◽  
Metabolic Processes ◽  
Lower Maximum ◽  
Non Photochemical Quenching ◽  
Oxide Synthase

ABSTRACTFibrillins (FBNs) are plastidial proteins found in photosynthetic organisms, from cyanobacteria to higher plants. The function of most FBNs is largely unknown. We focused on the subgroup formed by FBN1a, −1b, and −;2, which has been proposed to be involved in the photoprotection of photosystem II (PSII), though their mechanism of action has not yet been characterized. We show that FBN2 interacts with FBN1a and with other FBN2 polypeptides, potentially forming a network around the plastoglobule surface. Both FBN2 and FBN1 interact with the allene oxide synthase, and the elimination of any of these FBNs results in a delay in jasmonate-mediated anthocyanin accumulation in response to a combination of moderate-high light and low temperature. FBN2 also interacts with other proteins involved in different metabolic processes. Mutants lacking FBN2 demonstrate less photoprotection of PSII, alterations that are not found in fbn1a-fbn1b mutants. We also show that FBN2 interacts with Acclimation of Photosynthesis to Environment 1 (APE1), and gene co-expression analysis suggests that both proteins are involved in the same metabolic process. The elimination of APE1 leads to lesions in PSII under abiotic stress similar to observations in fbn2 mutants, with lower maximum and effective quantum yield. However, a reduction in non-photochemical quenching is observed exclusively in fbn2 mutants, suggesting that other FBN2-interacting proteins are responsible for this alteration. We propose that FBN2 facilitates accurate positioning of different proteins involved in distinct metabolic processes, and its elimination leads to dysfunction in those proteins.One sentence summaryFibrillin 2 protects photosynthesis against abiotic stresses by facilitating the accurate positioning of different proteins involved in distinct processes, and its elimination leads to dysfunction in those proteins

scholarly journals PsaK2 Subunit in Photosystem I Is Involved in State Transition under High Light Condition in the Cyanobacterium Synechocystis sp. PCC 6803

2005 ◽  
Vol 280 (23) ◽  
pp. 22191-22197 ◽  
Author(s):  
Tamaki Fujimori ◽  
Yukako Hihara ◽  
Kintake Sonoike
Keyword(s):  
Energy Transfer ◽  
Photosystem I ◽  
State Transition ◽  
Light Condition ◽  
High Light ◽  
Photochemical Quenching ◽  
Wild Type ◽  
Low Light ◽  
High Light Condition ◽  
Non Photochemical Quenching

To avoid the photodamage, cyanobacteria regulate the distribution of light energy absorbed by phycobilisome antenna either to photosystem II or to photosystem I (PSI) upon high light acclimation by the process so-called state transition. We found that an alternative PSI subunit, PsaK2 (sll0629 gene product), is involved in this process in the cyanobacterium Synechocystis sp. PCC 6803. An examination of the subunit composition of the purified PSI reaction center complexes revealed that PsaK2 subunit was absent in the PSI complexes under low light condition, but was incorporated into the complexes during acclimation to high light. The growth of the psaK2 mutant on solid medium was inhibited under high light condition. We determined the photosynthetic characteristics of the wild type strain and the two mutants, the psaK1 (ssr0390) mutant and the psaK2 mutant, using pulse amplitude modulation fluorometer. Non-photochemical quenching, which reflects the energy transfer from phycobilisome to PSI in cyanobacteria, was higher in high light grown cells than in low light grown cells, both in the wild type and the psaK1 mutant. However, this change of non-photochemical quenching during acclimation to high light was not observed in the psaK2 mutant. Thus, PsaK2 subunit is involved in the energy transfer from phycobilisome to PSI under high light condition. The role of PsaK2 in state transition under high light condition was also confirmed by chlorophyll fluorescence emission spectra determined at 77 K. The results suggest that PsaK2-dependent state transition is essential for the growth of this cyanobacterium under high light condition.

scholarly journals Restoration of Rapidly Reversible Photoprotective Energy Dissipation in the Absence of PsbS Protein by Enhanced ΔpH

2011 ◽  
Vol 286 (22) ◽  
pp. 19973-19981 ◽  
Author(s):  
Matthew P. Johnson ◽  
Alexander V. Ruban
Keyword(s):  
Higher Plants ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Reaction Centers ◽  
Photochemical Quenching ◽  
Spectral Changes ◽  
Intact Chloroplasts ◽  
Harvesting Process ◽  
Non Photochemical Quenching ◽  
Psbs Protein

Variations in the light environment require higher plants to regulate the light harvesting process. Under high light a mechanism known as non-photochemical quenching (NPQ) is triggered to dissipate excess absorbed light energy within the photosystem II (PSII) antenna as heat, preventing photodamage to the reaction center. The major component of NPQ, known as qE, is rapidly reversible in the dark and dependent upon the transmembrane proton gradient (ΔpH), formed as a result of photosynthetic electron transport. Using diaminodurene and phenazine metasulfate, mediators of cyclic electron flow around photosystem I, to enhance ΔpH, it is demonstrated that rapidly reversible qE-type quenching can be observed in intact chloroplasts from Arabidopsis plants lacking the PsbS protein, previously believed to be indispensible for the process. The qE in chloroplasts lacking PsbS significantly quenched the level of fluorescence when all PSII reaction centers were in the open state (Fo state), protected PSII reaction centers from photoinhibition, was modulated by zeaxanthin and was accompanied by the qE-typical absorption spectral changes, known as ΔA535. Titrations of the ΔpH dependence of qE in the absence of PsbS reveal that this protein affects the cooperativity and sensitivity of the photoprotective process to protons. The roles of PsbS and zeaxanthin are discussed in light of their involvement in the control of the proton-antenna association constant, pK, via regulation of the interconnected phenomena of PSII antenna reorganization/aggregation and hydrophobicity.

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