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Seydoux C, Storti M, Giovagnetti V, Matuszyńska A, Guglielmino E, Zhao X, Giustini C, Pan Y, Blommaert L, Angulo J, Ruban AV, Hu H, Bailleul B, Courtois F, Allorent G, Finazzi G. Impaired photoprotection in Phaeodactylum tricornutum KEA3 mutants reveals the proton regulatory circuit of diatoms light acclimation. New Phytol 2022; 234:578-591. [PMID: 35092009 PMCID: PMC9306478 DOI: 10.1111/nph.18003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 01/16/2022] [Indexed: 06/14/2023]
Abstract
Diatoms are successful phytoplankton clades able to acclimate to changing environmental conditions, including e.g. variable light intensity. Diatoms are outstanding at dissipating light energy exceeding the maximum photosynthetic electron transfer (PET) capacity via the nonphotochemical quenching (NPQ) process. While the molecular effectors of NPQ as well as the involvement of the proton motive force (PMF) in its regulation are known, the regulators of the PET/PMF relationship remain unidentified in diatoms. We generated mutants of the H+ /K+ antiporter KEA3 in the model diatom Phaeodactylum tricornutum. Loss of KEA3 activity affects the PET/PMF coupling and NPQ responses at the onset of illumination, during transients and in steady-state conditions. Thus, this antiporter is a main regulator of the PET/PMF coupling. Consistent with this conclusion, a parsimonious model including only two free components, KEA3 and the diadinoxanthin de-epoxidase, describes most of the feedback loops between PET and NPQ. This simple regulatory system allows for efficient responses to fast (minutes) or slow (e.g. diel) changes in light environment, thanks to the presence of a regulatory calcium ion (Ca2+ )-binding domain in KEA3 modulating its activity. This circuit is likely tuned by the NPQ-effector proteins, LHCXs, providing diatoms with the required flexibility to thrive in different ocean provinces.
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Affiliation(s)
- Claire Seydoux
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
| | - Mattia Storti
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
| | - Vasco Giovagnetti
- Departement of BiochemistryQueen Mary University of LondonMile End RoadLondonE14NSUK
| | - Anna Matuszyńska
- Computational Life ScienceDepartment of BiologyRWTH Aachen UniversityWorringer Weg 1Aachen52074Germany
| | | | - Xue Zhao
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
| | - Cécile Giustini
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
| | - Yufang Pan
- Key Laboratory of Algal BiologyInstitute of HydrobiologyChinese Academy of SciencesWuhan430072China
| | - Lander Blommaert
- Laboratory of Chloroplast Biology and Light Sensing in MicroalgaeInstitut de Biologie Physico ChimiqueCNRSSorbonne UniversitéParis75005France
| | - Jhoanell Angulo
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
| | - Alexander V. Ruban
- Departement of BiochemistryQueen Mary University of LondonMile End RoadLondonE14NSUK
| | - Hanhua Hu
- Key Laboratory of Algal BiologyInstitute of HydrobiologyChinese Academy of SciencesWuhan430072China
| | - Benjamin Bailleul
- Laboratory of Chloroplast Biology and Light Sensing in MicroalgaeInstitut de Biologie Physico ChimiqueCNRSSorbonne UniversitéParis75005France
| | | | | | - Giovanni Finazzi
- CNRSCEAINRAEIRIGLPCVUniversité Grenoble AlpesGrenoble38000France
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Giovagnetti V, Jaubert M, Shukla MK, Ungerer P, Bouly JP, Falciatore A, Ruban AV. Biochemical and molecular properties of LHCX1, the essential regulator of dynamic photoprotection in diatoms. Plant Physiol 2022; 188:509-525. [PMID: 34595530 PMCID: PMC8774712 DOI: 10.1093/plphys/kiab425] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 08/06/2021] [Indexed: 05/24/2023]
Abstract
Light harvesting is regulated by a process triggered by the acidification of the thylakoid lumen, known as nonphotochemical "energy-dependent quenching" (qE). In diatoms, qE is controlled by the light-harvesting complex (LHC) protein LHCX1, while the LHC stress-related (LHCSR) and photosystem II subunit S proteins are essential for green algae and plants, respectively. Here, we report a biochemical and molecular characterization of LHCX1 to investigate its role in qE. We found that, when grown under intermittent light, Phaeodactylum tricornutum forms very large qE, due to LHCX1 constitutive upregulation. This "super qE" is abolished in LHCX1 knockout mutants. Biochemical and spectroscopic analyses of LHCX1 reveal that this protein might differ in the character of binding pigments relative to the major pool of light-harvesting antenna proteins. The possibility of transient pigment binding or not binding pigments at all is discussed. Targeted mutagenesis of putative protonatable residues (D95 and E205) in transgenic P. tricornutum lines does not alter qE capacity, showing that they are not involved in sensing lumen pH, differently from residues conserved in LHCSR3. Our results suggest functional divergence between LHCX1 and LHCSR3 in qE modulation. We propose that LHCX1 evolved independently to facilitate dynamic tracking of light fluctuations in turbulent waters. The evolution of LHCX(-like) proteins in organisms with secondary red plastids, such as diatoms, might have conferred a selective advantage in the control of dynamic photoprotection, ultimately resulting in their ecological success.
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Affiliation(s)
- Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
| | - Marianne Jaubert
- Laboratoire de Biologie du Chloroplaste et Perception de la Lumière Chez les Micro-algues, UMR7141, CNRS, Sorbonne Université, Institut de Biologie Physico-Chimique, Paris 75005, France
| | - Mahendra K Shukla
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
| | - Petra Ungerer
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
| | - Jean-Pierre Bouly
- Laboratoire de Biologie du Chloroplaste et Perception de la Lumière Chez les Micro-algues, UMR7141, CNRS, Sorbonne Université, Institut de Biologie Physico-Chimique, Paris 75005, France
| | - Angela Falciatore
- Laboratoire de Biologie du Chloroplaste et Perception de la Lumière Chez les Micro-algues, UMR7141, CNRS, Sorbonne Université, Institut de Biologie Physico-Chimique, Paris 75005, France
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
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Shukla MK, Watanabe A, Wilson S, Giovagnetti V, Moustafa EI, Minagawa J, Ruban AV. A novel method produces native light-harvesting complex II aggregates from the photosynthetic membrane revealing their role in nonphotochemical quenching. J Biol Chem 2021; 295:17816-17826. [PMID: 33454016 DOI: 10.1074/jbc.ra120.016181] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/15/2020] [Indexed: 01/31/2023] Open
Abstract
Nonphotochemical quenching (NPQ) is a mechanism of regulating light harvesting that protects the photosynthetic apparatus from photodamage by dissipating excess absorbed excitation energy as heat. In higher plants, the major light-harvesting antenna complex (LHCII) of photosystem (PS) II is directly involved in NPQ. The aggregation of LHCII is proposed to be involved in quenching. However, the lack of success in isolating native LHCII aggregates has limited the direct interrogation of this process. The isolation of LHCII in its native state from thylakoid membranes has been problematic because of the use of detergent, which tends to dissociate loosely bound proteins, and the abundance of pigment-protein complexes (e.g. PSI and PSII) embedded in the photosynthetic membrane, which hinders the preparation of aggregated LHCII. Here, we used a novel purification method employing detergent and amphipols to entrap LHCII in its natural states. To enrich the photosynthetic membrane with the major LHCII, we used Arabidopsis thaliana plants lacking the PSII minor antenna complexes (NoM), treated with lincomycin to inhibit the synthesis of PSI and PSII core proteins. Using sucrose density gradients, we succeeded in isolating the trimeric and aggregated forms of LHCII antenna. Violaxanthin- and zeaxanthin-enriched complexes were investigated in dark-adapted, NPQ, and dark recovery states. Zeaxanthin-enriched antenna complexes showed the greatest amount of aggregated LHCII. Notably, the amount of aggregated LHCII decreased upon relaxation of NPQ. Employing this novel preparative method, we obtained a direct evidence for the role of in vivo LHCII aggregation in NPQ.
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Affiliation(s)
- Mahendra K Shukla
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Akimasa Watanabe
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki, Japan; Department of Basic Biology, School of Life Science, SOKENDAI, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Sam Wilson
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Ece Imam Moustafa
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki, Japan; Department of Basic Biology, School of Life Science, SOKENDAI, The Graduate University for Advanced Studies, Okazaki, Japan.
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
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Giovagnetti V, Ruban AV. The mechanism of regulation of photosystem I cross-section in the pennate diatom Phaeodactylum tricornutum. J Exp Bot 2021; 72:561-575. [PMID: 33068431 DOI: 10.1093/jxb/eraa478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/12/2020] [Indexed: 06/11/2023]
Abstract
Photosystems possess distinct fluorescence emissions at low (77K) temperature. PSI emits in the long-wavelength region at ~710-740 nm. In diatoms, a successful clade of marine primary producers, the contribution of PSI-associated emission (710-717 nm) has been shown to be relatively small. However, in the pennate diatom Phaeodactylum tricornutum, the source of the long-wavelength emission at ~710 nm (F710) remains controversial. Here, we addressed the origin and modulation of F710 fluorescence in this alga grown under continuous and intermittent light. The latter condition led to a strong enhancement in F710. Biochemical and spectral properties of the photosynthetic complexes isolated from thylakoid membranes were investigated for both culture conditions. F710 emission appeared to be associated with PSI regardless of light acclimation. To further assess whether PSII could also contribute to this emission, we decreased the concentration of PSII reaction centres and core antenna by growing cells with lincomycin, a chloroplast protein synthesis inhibitor. The treatment did not diminish F710 fluorescence. Our data suggest that F710 emission originates from PSI under the conditions tested and is enhanced in intermittent light-grown cells due to increased energy flow from the FCP antenna to PSI.
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Affiliation(s)
- Vasco Giovagnetti
- Department of Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Alexander V Ruban
- Department of Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
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Saccon F, Giovagnetti V, Shukla MK, Ruban AV. Rapid regulation of photosynthetic light harvesting in the absence of minor antenna and reaction centre complexes. J Exp Bot 2020; 71:3626-3637. [PMID: 32149343 PMCID: PMC7307847 DOI: 10.1093/jxb/eraa126] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/02/2020] [Indexed: 05/25/2023]
Abstract
Plants are subject to dramatic fluctuations in the intensity of sunlight throughout the day. When the photosynthetic machinery is exposed to high light, photons are absorbed in excess, potentially leading to oxidative damage of its delicate membrane components. A photoprotective molecular process called non-photochemical quenching (NPQ) is the fastest response carried out in the thylakoid membranes to harmlessly dissipate excess light energy. Despite having been intensely studied, the site and mechanism of this essential regulatory process are still debated. Here, we show that the main NPQ component called energy-dependent quenching (qE) is present in plants with photosynthetic membranes largely enriched in the major trimeric light-harvesting complex (LHC) II, while being deprived of all minor LHCs and most photosystem core proteins. This fast and reversible quenching depends upon thylakoid lumen acidification (ΔpH). Enhancing ΔpH amplifies the extent of the quenching and restores qE in the membranes lacking PSII subunit S protein (PsbS), whereas the carotenoid zeaxanthin modulates the kinetics and amplitude of the quenching. These findings highlight the self-regulatory properties of the photosynthetic light-harvesting membranes in vivo, where the ability to switch reversibly between the harvesting and dissipative states is an intrinsic property of the major LHCII.
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Affiliation(s)
- Francesco Saccon
- Queen Mary University of London, School of Biological and Chemical Sciences, London, UK
| | - Vasco Giovagnetti
- Queen Mary University of London, School of Biological and Chemical Sciences, London, UK
| | - Mahendra K Shukla
- Queen Mary University of London, School of Biological and Chemical Sciences, London, UK
| | - Alexander V Ruban
- Queen Mary University of London, School of Biological and Chemical Sciences, London, UK
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Giovagnetti V, Han G, Ware MA, Ungerer P, Qin X, Wang WD, Kuang T, Shen JR, Ruban AV. A siphonous morphology affects light-harvesting modulation in the intertidal green macroalga Bryopsis corticulans (Ulvophyceae). Planta 2018; 247:1293-1306. [PMID: 29460179 PMCID: PMC5945744 DOI: 10.1007/s00425-018-2854-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/20/2018] [Indexed: 05/18/2023]
Abstract
The macroalga Bryopsis corticulans relies on a sustained protective NPQ and a peculiar body architecture to efficiently adapt to the extreme light changes of intertidal shores. During low tides, intertidal algae experience prolonged high light stress. Efficient dissipation of excess light energy, measured as non-photochemical quenching (NPQ) of chlorophyll fluorescence, is therefore required to avoid photodamage. Light-harvesting regulation was studied in the intertidal macroalga Bryopsis corticulans, during high light and air exposure. Photosynthetic capacity and NPQ kinetics were assessed in different filament layers of the algal tufts and in intact chloroplasts to unravel the nature of NPQ in this siphonous green alga. We found that the morphology and pigment composition of the B. corticulans body provides functional segregation between surface sunlit filaments (protective state) and those that are underneath and undergo severe light attenuation (light-harvesting state). In the surface filaments, very high and sustained NPQ gradually formed. NPQ induction was triggered by the formation of transthylakoid proton gradient and independent of the xanthophyll cycle. PsbS and LHCSR proteins seem not to be active in the NPQ mechanism activated by this alga. Our results show that B. corticulans endures excess light energy pressure through a sustained protective NPQ, not related to photodamage, as revealed by the unusually quick restoration of photosystem II (PSII) function in the dark. This might suggest either the occurrence of transient PSII photoinactivation or a fast rate of PSII repair cycle.
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Affiliation(s)
- Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Guangye Han
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Maxwell A Ware
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Petra Ungerer
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Xiaochun Qin
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Wen-Da Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Tingyun Kuang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Jian-Ren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima, Naka, Okayama, 700-8530, Japan.
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
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Townsend AJ, Saccon F, Giovagnetti V, Wilson S, Ungerer P, Ruban AV. The causes of altered chlorophyll fluorescence quenching induction in the Arabidopsis mutant lacking all minor antenna complexes. Biochim Biophys Acta Bioenerg 2018; 1859:666-675. [PMID: 29548769 DOI: 10.1016/j.bbabio.2018.03.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/01/2018] [Accepted: 03/10/2018] [Indexed: 01/18/2023]
Abstract
Non-photochemical quenching (NPQ) of chlorophyll fluorescence is the process by which excess light energy is harmlessly dissipated within the photosynthetic membrane. The fastest component of NPQ, known as energy-dependent quenching (qE), occurs within minutes, but the site and mechanism of qE remain of great debate. Here, the chlorophyll fluorescence of Arabidopsis thaliana wild type (WT) plants was compared to mutants lacking all minor antenna complexes (NoM). Upon illumination, NoM exhibits altered chlorophyll fluorescence quenching induction (i.e. from the dark-adapted state) characterised by three different stages: (i) a fast quenching component, (ii) transient fluorescence recovery and (iii) a second quenching component. The initial fast quenching component originates in light harvesting complex II (LHCII) trimers and is dependent upon PsbS and the formation of a proton gradient across the thylakoid membrane (ΔpH). Transient fluorescence recovery is likely to occur in both WT and NoM plants, but it cannot be overcome in NoM due to impaired ΔpH formation and a reduced zeaxanthin synthesis rate. Moreover, an enhanced fluorescence emission peak at ~679 nm in NoM plants indicates detachment of LHCII trimers from the bulk antenna system, which could also contribute to the transient fluorescence recovery. Finally, the second quenching component is triggered by both ΔpH and PsbS and enhanced by zeaxanthin synthesis. This study indicates that minor antenna complexes are not essential for qE, but reveals their importance in electron stransport, ΔpH formation and zeaxanthin synthesis.
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Affiliation(s)
- Alexandra J Townsend
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Francesco Saccon
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Sam Wilson
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Petra Ungerer
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK.
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Sacharz J, Giovagnetti V, Ungerer P, Mastroianni G, Ruban AV. The xanthophyll cycle affects reversible interactions between PsbS and light-harvesting complex II to control non-photochemical quenching. Nat Plants 2017; 3:16225. [PMID: 28134919 DOI: 10.1038/nplants.2016.225] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 12/22/2016] [Indexed: 05/19/2023]
Abstract
To maintain high photosynthetic rates, plants must adapt to their light environment on a timescale of seconds to minutes. Therefore, the light-harvesting antenna system of photosystem II in thylakoid membranes, light-harvesting complex II (LHCII), has a feedback mechanism, which determines the proportion of absorbed energy dissipated as heat: non-photochemical chlorophyll fluorescence quenching (NPQ). This is crucial to prevent photo-oxidative damage to photosystem II (PSII) and is controlled by the transmembrane pH differences (ΔpH). High ΔpH activates NPQ by protonation of the protein PsbS and the enzymatic de-epoxidation of LHCII-bound violaxanthin to zeaxanthin. But the precise role of PsbS and its interactions with different LHCII complexes remain uncertain. We have investigated PsbS-LHCII interactions in native thylakoid membranes using magnetic-bead-linked antibody pull-downs. The interaction of PsbS with the antenna system is affected by both ΔpH and the level of zeaxanthin. In the presence of ΔpH alone, PsbS is found to be mainly associated with the trimeric LHCII protein polypeptides, Lhcb1, Lhcb2 and Lhcb3. However, a combination of ΔpH and zeaxanthin increases the proportion of PsbS bound to the minor LHCII antenna complex proteins Lhcb4, Lhcb5 and Lhcb6. This pattern of interaction is not influenced by the presence of PSII reactions centres. Similar to LHCII particles in the photosynthetic membrane, PsbS protein forms clusters in the NPQ state. NPQ recovery in the dark requires uncoupling of PsbS. We suggest that PsbS acts as a 'seeding' centre for the LHCII antenna rearrangement that is involved in NPQ.
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Affiliation(s)
- Joanna Sacharz
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Petra Ungerer
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Giulia Mastroianni
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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Giovagnetti V, Ruban AV. Detachment of the fucoxanthin chlorophyll a/c binding protein (FCP) antenna is not involved in the acclimative regulation of photoprotection in the pennate diatom Phaeodactylum tricornutum. Biochim Biophys Acta Bioenerg 2016; 1858:218-230. [PMID: 27989819 DOI: 10.1016/j.bbabio.2016.12.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/04/2016] [Accepted: 12/14/2016] [Indexed: 12/24/2022]
Abstract
When grown under intermittent light (IL), the pennate diatom Phaeodactylum tricornutum forms 'super' non-photochemical fluorescence quenching (NPQ) in response to excess light. The current model of diatom NPQ mechanism involves two quenching sites, one of which detaches from photosystem II reaction centres (RCIIs) and aggregates into oligomeric complexes. Here we addressed how antenna reorganisation controls NPQ kinetics in P. tricornutum cells grown under continuous light (CL) and IL. Overall, IL acclimation induced: (i) reorganisation of chloroplasts, containing greater pigment pools without a strongly enhanced operation of the xanthophyll cycle, and (ii) 'super NPQ' causing a remarkable reduction of the chlorophyll excited state lifetime at Fm'. Regardless of different levels of NPQ formed in both culture conditions, its dark recovery was rapid and similar fractions of their antenna uncoupled (~50%). Although antenna detachment relieved excitation pressure, it provided a minor protective contribution equivalent to NPQ~1, while the largest NPQ was 4.4±0.2 (CL) and 13±0.8 (IL). The PSII cross-section decrease took place only at relatively low NPQ values, beyond which the cross-section remained constant whilst NPQ continued to rise. This finding suggests that the energy trapping efficiency of diatom antenna quenchers cannot over-compete that of RCIIs, similarly to what has been observed on higher plants. We conclude that such 'economic photoprotection' operates to flexibly adjust the overall efficiency of diatom light harvesting.
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Affiliation(s)
- Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK.
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Giovagnetti V, Ware MA, Ruban AV. Assessment of the impact of photosystem I chlorophyll fluorescence on the pulse-amplitude modulated quenching analysis in leaves of Arabidopsis thaliana. Photosynth Res 2015; 125:179-89. [PMID: 25613087 DOI: 10.1007/s11120-015-0087-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 01/12/2015] [Indexed: 05/03/2023]
Abstract
In their natural environment, plants are exposed to varying light conditions, which can lead to a build-up of excitation energy in photosystem (PS) II. Non-photochemical quenching (NPQ) is the primary defence mechanism employed to dissipate this excess energy. Recently, we developed a fluorescence-quenching analysis procedure that enables the protective effectiveness of NPQ in intact Arabidopsis leaves to be determined. However, pulse-amplitude modulation measurements do not currently allow distinguishing between PSII and PSI fluorescence levels. Failure to account for PSI contribution is suggested to lead to inaccurate measurements of NPQ and, particularly, maximum PSII yield (F v/F m). Recently, Pfündel et al. (Photosynth Res 114:189-206, 2013) proposed a method that takes into account PSI contribution in the measurements of F o fluorescence level. However, when PSI contribution was assumed to be constant throughout the induction of NPQ, we observed lower values of the measured minimum fluorescence level ([Formula: see text]) than those calculated according to the formula of Oxborough and Baker (Photosynth Res 54:135-142 1997) ([Formula: see text]), regardless of the light intensity. Therefore, in this work, we propose a refined model to correct for the presence of PSI fluorescence, which takes into account the previously observed NPQ in PSI. This method efficiently resolves the discrepancies between measured and calculated F o' produced by assuming a constant PSI fluorescence contribution, whilst allowing for the correction of the maximum PSII yield.
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Affiliation(s)
- Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
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Ware MA, Giovagnetti V, Belgio E, Ruban AV. PsbS protein modulates non-photochemical chlorophyll fluorescence quenching in membranes depleted of photosystems. J Photochem Photobiol B 2015; 152:301-7. [PMID: 26233261 DOI: 10.1016/j.jphotobiol.2015.07.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/22/2015] [Accepted: 07/23/2015] [Indexed: 01/21/2023]
Abstract
Plants with varying levels of PsbS protein were grown on lincomycin. Enhanced levels of non-photochemical fluorescence quenching (NPQ) in over-expressers of the protein have been observed. This was accompanied by increased amplitude of the irreversible NPQ component, qI, previously considered to reflect mainly photoinhibition of PSII reaction centres (RCII). However, since RCIIs were largely absent the observed qI is likely to originate from the LHCII antenna. In chloroplasts of over-expressers of PsbS grown on lincomycin an abnormally large NPQ (∼7) was characterised by a 0.34 ns average chlorophyll fluorescence lifetime. Yet the lifetime in the Fm state was similar to that of wild-type plants. 77K fluorescence emission spectra revealed a specific 700 nm peak typical of LHCII aggregates as well as quenching of the PSI fluorescence at 730 nm. The aggregated state manifested itself as a clear change in the distance between LHCII complexes detected by freeze-fracture electron microscopy. Grana thylakoids in the quenched state revealed 3 times more aggregated LHCII particles compared to the dark-adapted state. Overall, the results directly demonstrate the importance of LHCII aggregation in the NPQ mechanism and show that the PSII supercomplex structure plays no role in formation of the observed quenching.
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Affiliation(s)
- Maxwell A Ware
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Vasco Giovagnetti
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Erica Belgio
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Alexander V Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
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Giovagnetti V, Flori S, Tramontano F, Lavaud J, Brunet C. The velocity of light intensity increase modulates the photoprotective response in coastal diatoms. PLoS One 2014; 9:e103782. [PMID: 25083713 PMCID: PMC4118909 DOI: 10.1371/journal.pone.0103782] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 07/07/2014] [Indexed: 12/21/2022] Open
Abstract
In aquatic ecosystems, the superimposition of mixing events to the light diel cycle exposes phytoplankton to changes in the velocity of light intensity increase, from diurnal variations to faster mixing-related ones. This is particularly true in coastal waters, where diatoms are dominant. This study aims to investigate if coastal diatoms differently activate the photoprotective responses, xanthophyll cycle (XC) and non-photochemical fluorescence quenching (NPQ), to cope with predictable light diel cycle and unpredictable mixing-related light variations. We compared the effect of two fast light intensity increases (simulating mixing events) with that of a slower increase (corresponding to the light diel cycle) on the modulation of XC and NPQ in the planktonic coastal diatom Pseudo-nitzschia multistriata. During each light treatment, the photon flux density (PFD) progressively increased from darkness to five peaks, ranging from 100 to 650 µmol photons m−2 s−1. Our results show that the diel cycle-related PFD increase strongly activates XC through the enhancement of the carotenoid biosynthesis and induces a moderate and gradual NPQ formation over the light gradient. In contrast, during mixing-related PFD increases, XC is less activated, while higher NPQ rapidly develops at moderate PFD. We observe that together with the light intensity and its increase velocity, the saturation light for photosynthesis (Ek) is a key parameter in modulating photoprotection. We propose that the capacity to adequately regulate and actuate alternative photoprotective ‘safety valves’ in response to changing velocity of light intensity increase further enhances the photophysiological flexibility of diatoms. This might be an evolutionary outcome of diatom adaptation to turbulent marine ecosystems characterized by unpredictable mixing-related light changes over the light diel cycle.
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Affiliation(s)
| | - Serena Flori
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, Italy
| | | | - Johann Lavaud
- Littoral Environnement et Sociétés, Unité Mixte de Recherche 7266, CNRS-Université de La Rochelle, La Rochelle, France
| | - Christophe Brunet
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, Italy
- * E-mail:
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Brunet C, Chandrasekaran R, Barra L, Giovagnetti V, Corato F, Ruban AV. Spectral radiation dependent photoprotective mechanism in the diatom Pseudo-nitzschia multistriata. PLoS One 2014; 9:e87015. [PMID: 24475212 PMCID: PMC3901731 DOI: 10.1371/journal.pone.0087015] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 12/16/2013] [Indexed: 11/18/2022] Open
Abstract
Phytoplankton, such as diatoms, experience great variations of photon flux density (PFD) and light spectrum along the marine water column. Diatoms have developed some rapidly-regulated photoprotective mechanisms, such as the xanthophyll cycle activation (XC) and the non-photochemical chlorophyll fluorescence quenching (NPQ), to protect themselves from photooxidative damages caused by excess PFD. In this study, we investigate the role of blue fluence rate in combination with red radiation in shaping photoacclimative and protective responses in the coastal diatom Pseudo-nitzschia multistriata. This diatom was acclimated to four spectral light conditions (blue, red, blue-red, blue-red-green), each of them provided with low and high PFD. Our results reveal that the increase in the XC pool size and the amplitude of NPQ is determined by the blue fluence rate experienced by cells, while cells require sensing red radiation to allow the development of these processes. Variations in the light spectrum and in the blue versus red radiation modulate either the photoprotective capacity, such as the activation of the diadinoxanthin-diatoxanthin xanthophyll cycle, the diadinoxanthin de-epoxidation rate and the capacity of non-photochemical quenching, or the pigment composition of this diatom. We propose that spectral composition of light has a key role on the ability of diatoms to finely balance light harvesting and photoprotective capacity.
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Affiliation(s)
- Christophe Brunet
- Laboratory of Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
- * E-mail:
| | - Raghu Chandrasekaran
- Laboratory of Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
| | - Lucia Barra
- Laboratory of Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
| | - Vasco Giovagnetti
- Laboratory of Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
| | - Federico Corato
- Laboratory of Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
| | - Alexander V. Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, United Kingdom
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