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Krishna K Niyogi - One of the best experts on this subject based on the ideXlab platform.
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dissecting and modeling zeaxanthin and lutein dependent Nonphotochemical Quenching in arabidopsis thaliana
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Krishna K Niyogi, Michelle Leuenberger, Jonathan M Morris, Arnold M Chan, Lauriebeth LeonelliAbstract:Photosynthetic organisms use various photoprotective mechanisms to dissipate excess photoexcitation as heat in a process called Nonphotochemical Quenching (NPQ). Regulation of NPQ allows for a rapid response to changes in light intensity and in vascular plants, is primarily triggered by a pH gradient across the thylakoid membrane (∆pH). The response is mediated by the PsbS protein and various xanthophylls. Time-correlated single-photon counting (TCSPC) measurements were performed on Arabidopsis thaliana to quantify the dependence of the response of NPQ to changes in light intensity on the presence and accumulation of zeaxanthin and lutein. Measurements were performed on WT and mutant plants deficient in one or both of the xanthophylls as well as a transgenic line that accumulates lutein via an engineered lutein epoxide cycle. Changes in the response of NPQ to light acclimation in WT and mutant plants were observed between two successive light acclimation cycles, suggesting that the character of the rapid and reversible response of NPQ in fully dark-acclimated plants is substantially different from in conditions plants are likely to experience caused by changes in light intensity during daylight. Mathematical models of the response of zeaxanthin- and lutein-dependent reversible NPQ were constructed that accurately describe the observed differences between the light acclimation periods. Finally, the WT response of NPQ was reconstructed from isolated components present in mutant plants with a single common scaling factor, which enabled deconvolution of the relative contributions of zeaxanthin- and lutein-dependent NPQ.
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a kinetic model of rapidly reversible Nonphotochemical Quenching
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Julia Zaks, Kapil Amarnath, David M Kramer, Graham R Fleming, Krishna K NiyogiAbstract:Oxygen-evolving photosynthetic organisms possess Nonphotochemical Quenching (NPQ) pathways that protect against photo-induced damage. The majority of NPQ in plants is regulated on a rapid timescale by changes in the pH of the thylakoid lumen. In order to quantify the rapidly reversible component of NPQ, called qE, we developed a mathematical model of pH-dependent Quenching of chlorophyll excitations in Photosystem II. Our expression for qE depends on the protonation of PsbS and the deepoxidation of violaxanthin by violaxanthin deepoxidase. The model is able to simulate the kinetics of qE at low and high light intensities. The simulations suggest that the pH of the lumen, which activates qE, is not itself affected by qE. Our model provides a framework for testing hypothesized qE mechanisms and for assessing the role of qE in improving plant fitness in variable light intensity.
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Toward an Understanding of the Mechanism of Nonphotochemical Quenching in Green Plants
Biochemistry, 2004Co-Authors: Nancy E Holt, Graham R Fleming, Krishna K NiyogiAbstract:Oxygenic photosynthesis in plants involves highly reactive intermediates and byproducts that can damage the photosynthetic apparatus and other chloroplast constituents. The potential for damage is exacerbated when the amount of absorbed light exceeds the capacity for light energy utilization in photosynthesis, a condition that can lead to decreases in photosynthetic efficiency. A feedback de-excitation mechanism (qE), measured as a component of Nonphotochemical Quenching of chlorophyll fluorescence, regulates photosynthetic light harvesting in excess light in response to a change in thylakoid lumen pH. qE involves de-excitation of the singlet excited state of chlorophyll in the light-harvesting antenna of photosystem II, thereby minimizing the deleterious effects of high light via thermal dissipation of excess excitation energy. While the physiological importance of qE has been recognized for many years, a description of its physical mechanism remains elusive. We summarize recent biochemical and spectroscopic results that have brought us closer to the goal of a mechanistic understanding of this fundamental photosynthetic regulatory process.
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toward an understanding of the mechanism of Nonphotochemical Quenching in green plants
Biochemistry, 2004Co-Authors: Nancy E Holt, Graham R Fleming, Krishna K NiyogiAbstract:Oxygenic photosynthesis in plants involves highly reactive intermediates and byproducts that can damage the photosynthetic apparatus and other chloroplast constituents. The potential for damage is exacerbated when the amount of absorbed light exceeds the capacity for light energy utilization in photosynthesis, a condition that can lead to decreases in photosynthetic efficiency. A feedback de-excitation mechanism (qE), measured as a component of Nonphotochemical Quenching of chlorophyll fluorescence, regulates photosynthetic light harvesting in excess light in response to a change in thylakoid lumen pH. qE involves de-excitation of the singlet excited state of chlorophyll in the light-harvesting antenna of photosystem II, thereby minimizing the deleterious effects of high light via thermal dissipation of excess excitation energy. While the physiological importance of qE has been recognized for many years, a description of its physical mechanism remains elusive. We summarize recent biochemical and spectrosc...
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molecular and global time resolved analysis of a psbs gene dosage effect on ph and xanthophyll cycle dependent Nonphotochemical Quenching in photosystem ii
Journal of Biological Chemistry, 2002Co-Authors: Xiaoping Li, Adam M Gilmore, Krishna K NiyogiAbstract:Abstract Photosynthetic light harvesting in plants is regulated by a pH- and xanthophyll-dependent Nonphotochemical Quenching process (qE) that dissipates excess absorbed light energy and requires the psbS gene product. AnArabidopsis thaliana mutant, npq4-1, lacks qE because of a deletion of the psbS gene, yet it exhibits a semidominant phenotype. Here it is shown that the semidominance is due to a psbS gene dosage effect. DiploidArabidopsis plants containing twopsbS gene copies (wild-type), one psbS gene (npq4-1/NPQ4 heterozygote), and no psbS gene (npq4-1/npq4-1 homozygote) were compared. Heterozygous plants had 56% of the wild-type psbS mRNA level, 58% of the wild-type PsbS protein level, and 60% of the wild-type level of qE. Global analysis of the chlorophyll a fluorescence lifetime distributions revealed three components in wild-type and heterozygous plants, but only a single long lifetime component innpq4-1. The short lifetime distribution associated with qE was inhibited by more than 40% in heterozygous plants compared with the wild type. Thus, the extent of qE measured as either the fractional intensities of the PSII chlorophyll afluorescence lifetime distributions or steady state intensities was stoichiometrically related to the amount of PsbS protein.
Peter Horton - One of the best experts on this subject based on the ideXlab platform.
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the zeaxanthin independent and zeaxanthin dependent qe components of Nonphotochemical Quenching involve common conformational changes within the photosystem ii antenna in arabidopsis
Plant Physiology, 2008Co-Authors: Matthew P Johnson, Peter Horton, Maria L Perezbueno, Alexander V RubanAbstract:The light-harvesting antenna of higher plant photosystem II (LHCII) has the intrinsic capacity to dissipate excess light energy as heat in a process termed Nonphotochemical Quenching (NPQ). Recent studies suggest that zeaxanthin and lutein both contribute to the rapidly relaxing component of NPQ, qE, possibly acting in the minor monomeric antenna complexes and the major trimeric LHCII, respectively. To distinguish whether zeaxanthin and lutein act independently as quenchers at separate sites, or alternatively whether zeaxanthin fulfills an allosteric role regulating lutein-mediated Quenching, the kinetics of qE and the qE-related conformational changes (ΔA535) were compared in Arabidopsis (Arabidopsis thaliana) mutant/antisense plants with altered contents of minor antenna (kolhcb6, aslhcb4), trimeric LHCII (aslhcb2), lutein (lut2, lut2npq1, lut2npq2), and zeaxanthin (npq1, npq2). The kinetics of the two components of NPQ induction arising from zeaxanthin-independent and zeaxanthin-dependent qE were both sensitive to changes in the protein composition of the photosystem II antenna. The replacement of lutein by zeaxanthin or violaxanthin in the internal Lhcb protein-binding sites affected the kinetics and relative amplitude of each component as well as the absolute chlorophyll fluorescence lifetime. Both components of qE were characterized by a conformational change leading to nearly identical absorption changes in the Soret region that indicated the involvement of the LHCII lutein 1 domain. Based on these observations, we suggest that both components of qE arise from a common Quenching mechanism based upon a conformational change within the photosystem II antenna, optimized by Lhcb subunit-subunit interactions and tuned by the synergistic effects of external and internally bound xanthophylls.
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Photosynthetic acclimation: Does the dynamic structure and macro‐organisation of photosystem II in higher plant grana membranes regulate light harvesting states?
FEBS Journal, 2008Co-Authors: Peter Horton, Matthew P Johnson, María L. Pérez-bueno, Anett Z. Kiss, Alexander V RubanAbstract:The efficiency of light harvesting in higher plant photosynthesis is regulated in response to external environmental conditions. Under conditions of excess light, the normally highly efficient light-harvesting system of photosystem II is switched into a state in which unwanted, potentially harmful, energy is dissipated as heat. This process, known as Nonphotochemical Quenching, occurs by the creation of energy quenchers following conformational change in the light-harvesting complexes, which is initiated by the build up of the thylakoid pH gradient and controlled by the xanthophyll cycle. In the present study, the evidence to support the notion that this regulatory mechanism is dependent upon the organization of the different antenna subunits in the stacked grana membranes is reviewed. We postulate that Nonphotochemical Quenching occurs within a structural locus comprising the PsbS subunit and components of the light-harvesting antenna, CP26, CP24, CP29 and LHCIIb (the major trimeric light-harvesting complex), formed in response to protonation and controlled by the xanthophyll cycle carotenoids.
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psbs enhances Nonphotochemical fluorescence Quenching in the absence of zeaxanthin
FEBS Letters, 2006Co-Authors: Sophie Crouchman, Alexander V Ruban, Peter HortonAbstract:Abstract Leaves and chloroplasts from Arabidopsis plants with increased amounts of PsbS protein showed the same percentage increase in Nonphotochemical Quenching in comparison to the wild type both in the presence and absence of zeaxanthin. The absorption change at 525–535 nm was also more pronounced in both cases. It is suggested that PsbS alone can cause the Quenching, supporting the model in which zeaxanthin acts as an allosteric activator and is not the primary cause of the process. It is proposed that PsbS acts as a trigger of the conformational change that leads to the establishment of Nonphotochemical Quenching.
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kinetic analysis of Nonphotochemical Quenching of chlorophyll fluorescence 1 isolated chloroplasts
Biochemistry, 2001Co-Authors: Alexander V Ruban, Mark Wentworth, Peter HortonAbstract:Nonphotochemical Quenching of chlorophyll fluorescence in plants is indicative of a process that dissipates excess excitation energy from the light-harvesting antenna of photosystem II. The major fraction of Quenching is obligatorily dependent upon the thylakoid ΔpH and is regulated by the de-epoxidation state of the xanthophyll cycle carotenoids associated with the light-harvesting complexes. Basic principles of enzyme kinetics have been used to investigate this process in isolated chloroplasts. The extent of Quenching was titrated against the estimated thylakoid lumen pH, and a sigmoidal relationship was obtained with a Hill coefficient of 4.5 and a pK of 4.7. Upon de-epoxidation, these parameters changed to 1.6 and 5.7, respectively. Antimycin A suppressed Quenching, increasing the Hill coefficient and reducing the pK. The rate of induction of Quenching fitted second-order kinetics with respect to illumination time, and the rate constant was dependent upon the ΔpH, the de-epoxidation state, the presenc...
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kinetic analysis of Nonphotochemical Quenching of chlorophyll fluorescence 2 isolated light harvesting complexes
Biochemistry, 2001Co-Authors: Mark Wentworth, Alexander V Ruban, Peter HortonAbstract:The chlorophyll fluorescence yield of purified photosystem II light-harvesting complexes can be lowered by manipulation of experimental conditions. In several important respects, this Quenching resembles the Nonphotochemical Quenching observed in isolated chloroplasts and leaves, therefore providing a model system for investigating the underlying mechanism. A methodology based on the principles of enzyme kinetic analysis has already been applied to isolated chloroplasts, and this same experimental approach was used here with purified LHCIIb, CP26, and CP29. It was found that the kinetics of the decrease in fluorescence yield robustly fitted a second-order kinetic model with respect to time after induction of Quenching. The second-order rate constant was dependent upon the complex that was analyzed, the detergent concentration, the solution pH, and the presence of exogenous xanthophyll cycle carotenoids. In contrast, the formation of an absorbance change at 683 nm that accompanies Quenching displayed first...
Graham R Fleming - One of the best experts on this subject based on the ideXlab platform.
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snapshot transient absorption spectroscopy toward in vivo investigations of Nonphotochemical Quenching mechanisms
Photosynthesis Research, 2019Co-Authors: Soomin Park, Graham R Fleming, Collin J Steen, Alexandra L FischerAbstract:Although the importance of Nonphotochemical Quenching (NPQ) on photosynthetic biomass production and crop yields is well established, the in vivo operation of the individual mechanisms contributing to overall NPQ is still a matter of controversy. In order to investigate the timescale and activation dynamics of specific Quenching mechanisms, we have developed a technique called snapshot transient absorption (TA) spectroscopy, which can monitor molecular species involved in the Quenching response with a time resolution of 30 s. Using intact thylakoid membrane samples, we show how conventional TA kinetic and spectral analyses enable the determination of the appropriate wavelength and time delay for snapshot TA experiments. As an example, we show how the chlorophyll-carotenoid charge transfer and excitation energy transfer mechanisms can be monitored based on signals corresponding to the carotenoid (Car) radical cation and Car S1 excited state absorption, respectively. The use of snapshot TA spectroscopy together with the previously reported fluorescence lifetime snapshot technique (Sylak-Glassman et al. in Photosynth Res 127:69–76, 2016) provides valuable information such as the concurrent appearance of specific Quenching species and overall Quenching of excited Chl. Furthermore, we show that the snapshot TA technique can be successfully applied to completely intact photosynthetic organisms such as live cells of Nannochloropsis. This demonstrates that the snapshot TA technique is a valuable method for tracking the dynamics of intact samples that evolve over time, such as the photosynthetic system in response to high-light exposure.
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Comparing the photophysics of the two forms of the Orange Carotenoid Protein using 2D electronic spectroscopy
EPJ Web of Conferences, 2013Co-Authors: Gabriela S. Schlau-cohen, Vanessa Margaret Huxter, Ryan L. Leverenz, Richard A. Mathies, Graham R FlemingAbstract:Broadband two-dimensional electronic spectroscopy is applied to investigate the photophysics of the photoactive orange carotenoid protein, which is involved in Nonphotochemical Quenching in cyanobacteria. Differences in dynamics between the light and dark forms arise from the different structure of the carotenoid in the protein pocket, with consequences for the biological role of the two forms.
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a kinetic model of rapidly reversible Nonphotochemical Quenching
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Julia Zaks, Kapil Amarnath, David M Kramer, Graham R Fleming, Krishna K NiyogiAbstract:Oxygen-evolving photosynthetic organisms possess Nonphotochemical Quenching (NPQ) pathways that protect against photo-induced damage. The majority of NPQ in plants is regulated on a rapid timescale by changes in the pH of the thylakoid lumen. In order to quantify the rapidly reversible component of NPQ, called qE, we developed a mathematical model of pH-dependent Quenching of chlorophyll excitations in Photosystem II. Our expression for qE depends on the protonation of PsbS and the deepoxidation of violaxanthin by violaxanthin deepoxidase. The model is able to simulate the kinetics of qE at low and high light intensities. The simulations suggest that the pH of the lumen, which activates qE, is not itself affected by qE. Our model provides a framework for testing hypothesized qE mechanisms and for assessing the role of qE in improving plant fitness in variable light intensity.
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kinetic model for assessing the effect of ph dependent Nonphotochemical Quenching of chlorophyll excitations on the energetic output of chloroplasts
Biophysical Journal, 2012Co-Authors: Julia Zaks, Kapil Amarnath, David M Kramer, Krishna K Niygoi, Graham R FlemingAbstract:The controlled dissipation of chlorophyll excitations protects photosynthetic organisms from inhibition of photosystem II. This dissipation, commonly known as Nonphotochemical Quenching (NPQ), enhances plants' fitness in natural conditions where sunlight intensity fluctuates. To identify the properties of feedback loop(s) controlling NPQ that enable it to effectively balance light harvesting and photoprotection, we have developed a mathematical model of photosystem II that incorporates molecular mechanisms for Nonphotochemical Quenching containing the PsbS protein and the xanthophyll cycle. The model accurately reproduces measurements of chlorophyll fluorescence over several minutes in intact leaves of the plant Arabidopsis thaliana. The model enables calculation of the effect of NPQ on both photoinhibition and energy consumption by the carbon reactions. This calculation provides a framework for quantifying the role of feedback-regulated photoprotection in enhancing the ability of plants to thrive in variable light conditions. Because the model incorporates mechanistic details, it has the potential to inform on modifications to improve the feedback loop controlling rapid Nonphotochemical Quenching to optimize the role of PSII regulation in maximizing biomass production.
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lutein accumulation in the absence of zeaxanthin restores Nonphotochemical Quenching in the arabidopsis thaliana npq1 mutant
The Plant Cell, 2009Co-Authors: David M Kramer, Graham R Fleming, Roberto Bassi, Matteo Ballottari, Zhirong Li, Thomas J Avenson, Jeffrey A Cruz, Jay D KeaslingAbstract:Plants protect themselves from excess absorbed light energy through thermal dissipation, which is measured as Nonphotochemical Quenching of chlorophyll fluorescence (NPQ). The major component of NPQ, qE, is induced by high transthylakoid DpH in excess light and depends on the xanthophyll cycle, in which violaxanthin and antheraxanthin are deepoxidized to form zeaxanthin. To investigate the xanthophyll dependence of qE, we identified suppressor of zeaxanthinless1 (szl1) as a suppressor of the Arabidopsis thaliana npq1 mutant, which lacks zeaxanthin. szl1 npq1 plants have a partially restored qE but lack zeaxanthin and have low levels of violaxanthin, antheraxanthin, and neoxanthin. However, they accumulate more lutein and a-carotene than the wild type. szl1 contains a point mutation in the lycopene b-cyclase (LCYB) gene. Based on the pigment analysis, LCYB appears to be the major lycopene b-cyclase and is not involved in neoxanthin synthesis. The Lhcb4 (CP29) and Lhcb5 (CP26) protein levels are reduced by 50% in szl1 npq1 relative to the wild type, whereas other Lhcb proteins are present at wild-type levels. Analysis of carotenoid radical cation formation and leaf absorbance changes strongly suggest that the higher amount of lutein substitutes for zeaxanthin in qE, implying a direct role in qE, as well as a mechanism that is weakly sensitive to carotenoid structural properties.
Roberta Croce - One of the best experts on this subject based on the ideXlab platform.
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ph dependence kinetics and light harvesting regulation of Nonphotochemical Quenching in chlamydomonas
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Lijin Tian, Wojciech J Nawrocki, Iryna Polukhina, Ivo H M Van Stokkum, Roberta CroceAbstract: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.
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revisiting the role of xanthophylls in Nonphotochemical Quenching
Journal of Physical Chemistry Letters, 2018Co-Authors: Bart Van Oort, Pengqi Xu, Yinghong Lu, Daniel Karcher, Ralph Bock, Roberta CroceAbstract:Photoprotective Nonphotochemical Quenching (NPQ) of absorbed solar energy is vital for survival of photosynthetic organisms, and NPQ modifications significantly improve plant productivity. However, the exact NPQ Quenching mechanism is obscured by discrepancies between reported mechanisms, involving xanthophyll–chlorophyll (Xan–Chl) and Chl–Chl interactions. We present evidence of an experimental artifact that may explain the discrepancies: strong laser pulses lead to the formation of a novel electronic species in the major plant light-harvesting complex (LHCII). This species evolves from a high excited state of Chl a and is absent with weak laser pulses. It resembles an excitonically coupled heterodimer of Chl a and lutein (or other Xans at site L1) and acts as a de-excitation channel. Laser powers, and consequently amounts of artifact, vary strongly between NPQ studies, thereby explaining contradicting spectral signatures attributed to NPQ. Our results offer pathways toward unveiling NPQ mechanisms and h...
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Leaf and Plant Age Affects Photosynthetic Performance and Photoprotective Capacity
Plant Physiology, 2017Co-Authors: Ludwik W. Bielczynski, Mateusz Krzysztof Łącki, Iris Hoefnagels, Anna Gambin, Roberta CroceAbstract:In this work, we studied the changes in high-light tolerance and photosynthetic activity in leaves of the Arabidopsis (Arabidopsis thaliana) rosette throughout the vegetative stage of growth. We implemented an image-analysis work flow to analyze the capacity of both the whole plant and individual leaves to cope with excess excitation energy by following the changes in absorbed light energy partitioning. The data show that leaf and plant age are both important factors influencing the fate of excitation energy. During the dark-to-light transition, the age of the plant affects mostly steady-state levels of photochemical and Nonphotochemical Quenching, leading to an increased photosynthetic performance of its leaves. The age of the leaf affects the induction kinetics of Nonphotochemical Quenching. These observations were confirmed using model selection procedures. We further investigated how different leaves on a rosette acclimate to high light and show that younger leaves are less prone to photoinhibition than older leaves. Our results stress that both plant and leaf age should be taken into consideration during the quantification of photosynthetic and photoprotective traits to produce repeatable and reliable results.
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zeaxanthin dependent Nonphotochemical Quenching does not occur in photosystem i in the higher plant arabidopsis thaliana
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Lijin Tian, Alfred R Holzwarth, Pengqi Xu, Volha U Chukhutsina, Roberta CroceAbstract:Abstract Nonphotochemical Quenching (NPQ) is the process that protects the photosynthetic apparatus of plants and algae from photodamage by dissipating as heat the energy absorbed in excess. Studies on NPQ have almost exclusively focused on photosystem II (PSII), as it was believed that NPQ does not occur in photosystem I (PSI). Recently, Ballottari et al. [Ballottari M, et al. (2014) Proc Natl Acad Sci USA 111:E2431–E2438], analyzing PSI particles isolated from an Arabidopsis thaliana mutant that accumulates zeaxanthin constitutively, have reported that this xanthophyll can efficiently induce chlorophyll fluorescence Quenching in PSI. In this work, we have checked the biological relevance of this finding by analyzing WT plants under high-light stress conditions. By performing time-resolved fluorescence measurements on PSI isolated from Arabidopsis thaliana WT in dark-adapted and high-light–stressed (NPQ) states, we find that the fluorescence kinetics of both PSI are nearly identical. To validate this result in vivo, we have measured the kinetics of PSI directly on leaves in unquenched and NPQ states; again, no differences were observed. It is concluded that PSI does not undergo NPQ in biologically relevant conditions in Arabidopsis thaliana. The possible role of zeaxanthin in PSI photoprotection is discussed.
Roberto Bassi - One of the best experts on this subject based on the ideXlab platform.
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high light dependent phosphorylation of photosystem ii inner antenna cp29 in monocots is stn7 independent and enhances Nonphotochemical Quenching
Plant Physiology, 2015Co-Authors: Nico Betterle, Matteo Ballottari, Sacha Baginsky, Roberto BassiAbstract:Phosphorylation of the photosystem II antenna protein CP29 has been reported to be induced by excess light and further enhanced by low temperature, increasing resistance to these stressing factors. Moreover, high light-induced CP29 phosphorylation was specifically found in monocots, both C3 and C4, which include the large majority of food crops. Recently, knockout collections have become available in rice (Oryza sativa), a model organism for monocots. In this work, we have used reverse genetics coupled to biochemical and physiological analysis to elucidate the molecular basis of high light-induced phosphorylation of CP29 and the mechanisms by which it exerts a photoprotective effect. We found that kinases and phosphatases involved in CP29 phosphorylation are distinct from those reported to act in State 1-State 2 transitions. In addition, we elucidated the photoprotective role of CP29 phosphorylation in reducing singlet oxygen production and enhancing excess energy dissipation. We thus established, in monocots, a mechanistic connection between phosphorylation of CP29 and Nonphotochemical Quenching, two processes so far considered independent from one another.
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zeaxanthin binds to light harvesting complex stress related protein to enhance Nonphotochemical Quenching in physcomitrella patens
The Plant Cell, 2013Co-Authors: Alberta Pinnola, Luca Dallosto, Roberto Bassi, Caterina Gerotto, Tomas Morosinotto, Alessandro AlboresiAbstract:Nonphotochemical Quenching (NPQ) dissipates excess energy to protect the photosynthetic apparatus from excess light. The moss Physcomitrella patens exhibits strong NPQ by both algal-type light-harvesting complex stress-related (LHCSR)–dependent and plant-type S subunit of Photosystem II (PSBS)-dependent mechanisms. In this work, we studied the dependence of NPQ reactions on zeaxanthin, which is synthesized under light stress by violaxanthin deepoxidase (VDE) from preexisting violaxanthin. We produced vde knockout (KO) plants and showed they underwent a dramatic reduction in thermal dissipation ability and enhanced photoinhibition in excess light conditions. Multiple mutants ( vde lhcsr KO and vde psbs KO) showed that zeaxanthin had a major influence on LHCSR-dependent NPQ, in contrast with previous reports in Chlamydomonas reinhardtii . The PSBS-dependent component of Quenching was less dependent on zeaxanthin, despite the near-complete violaxanthin to zeaxanthin exchange in LHC proteins. Consistent with this, we provide biochemical evidence that native LHCSR protein binds zeaxanthin upon excess light stress. These findings suggest that zeaxanthin played an important role in the adaptation of modern plants to the enhanced levels of oxygen and excess light intensity of land environments.
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lutein accumulation in the absence of zeaxanthin restores Nonphotochemical Quenching in the arabidopsis thaliana npq1 mutant
The Plant Cell, 2009Co-Authors: David M Kramer, Graham R Fleming, Roberto Bassi, Matteo Ballottari, Zhirong Li, Thomas J Avenson, Jeffrey A Cruz, Jay D KeaslingAbstract:Plants protect themselves from excess absorbed light energy through thermal dissipation, which is measured as Nonphotochemical Quenching of chlorophyll fluorescence (NPQ). The major component of NPQ, qE, is induced by high transthylakoid DpH in excess light and depends on the xanthophyll cycle, in which violaxanthin and antheraxanthin are deepoxidized to form zeaxanthin. To investigate the xanthophyll dependence of qE, we identified suppressor of zeaxanthinless1 (szl1) as a suppressor of the Arabidopsis thaliana npq1 mutant, which lacks zeaxanthin. szl1 npq1 plants have a partially restored qE but lack zeaxanthin and have low levels of violaxanthin, antheraxanthin, and neoxanthin. However, they accumulate more lutein and a-carotene than the wild type. szl1 contains a point mutation in the lycopene b-cyclase (LCYB) gene. Based on the pigment analysis, LCYB appears to be the major lycopene b-cyclase and is not involved in neoxanthin synthesis. The Lhcb4 (CP29) and Lhcb5 (CP26) protein levels are reduced by 50% in szl1 npq1 relative to the wild type, whereas other Lhcb proteins are present at wild-type levels. Analysis of carotenoid radical cation formation and leaf absorbance changes strongly suggest that the higher amount of lutein substitutes for zeaxanthin in qE, implying a direct role in qE, as well as a mechanism that is weakly sensitive to carotenoid structural properties.
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Nonphotochemical Quenching of chlorophyll fluorescence in chlamydomonas reinhardtii
Biochemistry, 2006Co-Authors: Giovanni Finazzi, Giles N Johnson, Luca Dallosto, Francesca Zito, Giulia Bonente, Roberto Bassi, Francis Andre WollmanAbstract:Unlike plants, Chlamydomonas reinhardtii shows a restricted ability to develop Nonphotochemical Quenching upon illumination. Most of this limited Quenching is due to state transitions instead of ΔpH-driven high-energy state Quenching, qE. The latter could only be observed when the ability of the cells to perform photosynthesis was impaired, either by lowering temperature to ∼0 °C or in mutants lacking RubisCO activity. Two main features were identified that account for the low level of qE in Chlamydomonas. On one hand, the electrochemical proton gradient generated upon illumination is apparently not sufficient to promote fluorescence Quenching. On the other hand, the capacity to transduce the presence of a ΔpH into a Quenching response is also intrinsically decreased in this alga, when compared to plants. The possible mechanism leading to these differences is discussed.
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a zeaxanthin independent Nonphotochemical Quenching mechanism localized in the photosystem ii core complex
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Giovanni Finazzi, Giles N Johnson, Luca Dallosto, Francis Andre Wollman, Pierre Joliot, Roberto BassiAbstract:Illumination of dark-adapted barley plants with low light transiently induced a large Nonphotochemical Quenching of chlorophyll fluorescence. This reaction was identified as a form of high-energy-state Quenching. Its appearance was not accompanied by zeaxanthin synthesis but was associated with a reversible inactivation of a fraction of photosystem II (PSII) centers. Both the fluorescence Quenching and PSII inactivation relaxed in parallel with the activation of the Calvin cycle. We interpret the induction of this phenomenon as due to the generation of a quenched state in the PSII core complex. This reaction is probably caused by the transient overacidification of the thylakoid lumen, whereas its dissipation results from the relaxation of both the pH gradient across the thylakoid membrane and redox pressure upon activation of carbon fixation. At saturating light intensities, inactivation of PSII was still observed at the onset of illumination, although its recovery did not result in dissipation of high-energy Quenching, which presents typical characteristics of an antenna-associated Quenching at steady state. Reaction-center Quenching seems therefore to be a common transient feature during illumination, being replaced by other phenomena (photochemical or antenna Quenching and photoinhibition), depending on the balance between light and carbon fixation fluxes.
