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Fadeeva M, Klaiman D, Kandiah E, Nelson N. Structure of native photosystem II assembly intermediate from Chlamydomonas reinhardtii. Front Plant Sci 2024; 14:1334608. [PMID: 38322422 PMCID: PMC10844431 DOI: 10.3389/fpls.2023.1334608] [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] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/04/2023] [Indexed: 02/08/2024]
Abstract
Chlamydomonas reinhardtii Photosystem II (PSII) is a dimer consisting of at least 13 nuclear-encoded and four chloroplast-encoded protein subunits that collectively function as a sunlight-driven oxidoreductase. In this study, we present the inaugural structure of a green alga PSII assembly intermediate (pre-PSII-int). This intermediate was isolated from chloroplast membranes of the temperature-sensitive mutant TSP4, cultivated for 14 hours at a non-permissive temperature. The assembly state comprises a monomer containing subunits A, B, C, D, E, F, H, I, K, and two novel assembly factors, Psb1 and Psb2. Psb1 is identified as a novel transmembrane helix located adjacent to PsbE and PsbF (cytochrome b559). The absence of PsbJ, typically found in mature PSII close to this position, indicates that Psb1 functions as an assembly factor. Psb2 is an eukaryotic homolog of the cyanobacterial assembly factor Psb27. The presence of iron, coupled with the absence of QA, QB, and the manganese cluster, implies a protective mechanism against photodamage and provides insights into the intricate assembly process.
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Affiliation(s)
- Mariia Fadeeva
- The George S. Wise Faculty of Life Sciences, Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Daniel Klaiman
- The George S. Wise Faculty of Life Sciences, Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Eaazhisai Kandiah
- CM01 Beamline, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Nathan Nelson
- The George S. Wise Faculty of Life Sciences, Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
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Feng Y, Li Z, Li X, Shen L, Liu X, Zhou C, Zhang J, Sang M, Han G, Yang W, Kuang T, Wang W, Shen JR. Structure of a diatom photosystem II supercomplex containing a member of Lhcx family and dimeric FCPII. Sci Adv 2023; 9:eadi8446. [PMID: 37878698 PMCID: PMC10599620 DOI: 10.1126/sciadv.adi8446] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 05/22/2023] [Accepted: 09/23/2023] [Indexed: 10/27/2023]
Abstract
Diatoms rely on fucoxanthin chlorophyll a/c-binding proteins (FCPs) for their great success in oceans, which have a great diversity in their pigment, protein compositions, and subunit organizations. We report a unique structure of photosystem II (PSII)-FCPII supercomplex from Thalassiosira pseudonana at 2.68-Å resolution by cryo-electron microscopy. FCPIIs within this PSII-FCPII supercomplex exist in dimers and monomers, and a homodimer and a heterodimer were found to bind to a PSII core. The FCPII homodimer is formed by Lhcf7 and associates with PSII through an Lhcx family antenna Lhcx6_1, whereas the heterodimer is formed by Lhcf6 and Lhcf11 and connects to the core together with an Lhcf5 monomer through Lhca2 monomer. An extended pigment network consisting of diatoxanthins, diadinoxanthins, fucoxanthins, and chlorophylls a/c is revealed, which functions in efficient light harvesting, energy transfer, and dissipation. These results provide a structural basis for revealing the energy transfer and dissipation mechanisms and also for the structural diversity of FCP antennas in diatoms.
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Affiliation(s)
- Yue Feng
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhenhua Li
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoyi Li
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- China National Botanical Garden, Beijing 100093, China
| | - Lili Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xueyang Liu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Cuicui Zhou
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinyang Zhang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Min Sang
- China National Botanical Garden, Beijing 100093, China
| | - Guangye Han
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- China National Botanical Garden, Beijing 100093, China
| | - Wenqiang Yang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- China National Botanical Garden, Beijing 100093, China
| | - Tingyun Kuang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- China National Botanical Garden, Beijing 100093, China
| | - Wenda Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- China National Botanical Garden, 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, Okayama 700-8530, Japan
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Milrad Y, Nagy V, Elman T, Fadeeva M, Tóth SZ, Yacoby I. A PSII photosynthetic control is activated in anoxic cultures of green algae following illumination. Commun Biol 2023; 6:514. [PMID: 37173420 PMCID: PMC10182038 DOI: 10.1038/s42003-023-04890-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 05/01/2023] [Indexed: 05/15/2023] Open
Abstract
Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O2 which diminishes the expression and the activity of the hydrogenase enzyme catalyzing H2 production. Here we report a third, hitherto unknown challenge: We found that under anoxia, a slow-down switch is activated in photosystem II (PSII), diminishing the maximal photosynthetic productivity by three-fold. Using purified PSII and applying in vivo spectroscopic and mass spectrometric techniques on Chlamydomonas reinhardtii cultures, we show that this switch is activated under anoxia, within 10 s of illumination. Furthermore, we show that the recovery to the initial rate takes place following 15 min of dark anoxia, and propose a mechanism in which, modulation in electron transfer at the acceptor site of PSII diminishes its output. Such insights into the mechanism broaden our understanding of anoxic photosynthesis and its regulation in green algae and inspire new strategies to improve bio-energy yields.
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Affiliation(s)
- Yuval Milrad
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Valéria Nagy
- Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, H-6726 Szeged, Hungary
| | - Tamar Elman
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Maria Fadeeva
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Szilvia Z Tóth
- Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, H-6726 Szeged, Hungary
| | - Iftach Yacoby
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel.
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Wilson S, Kim E, Ishii A, Ruban AV, Minagawa J. Overexpression of LHCSR and PsbS enhance light tolerance in Chlamydomonas reinhardtii. J Photochem Photobiol B 2023; 244:112718. [PMID: 37156084 DOI: 10.1016/j.jphotobiol.2023.112718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 04/17/2023] [Accepted: 05/01/2023] [Indexed: 05/10/2023]
Abstract
Nonphotochemical quenching (NPQ) is a crucial mechanism for fine-tuning light harvesting and protecting the photosystem II (PSII) reaction centres from excess light energy in plants and algae. This process is regulated by photoprotective proteins LHCSR1, LHCSR3, and PsbS in green algae, such as Chlamydomonas reinhardtii. The det1-2 phot mutant, which overexpresses these photoprotective proteins, resulting in a significantly higher NPQ response, has been recently discovered in C. reinhardtii. Here, we analysed the physiological impact of this response on algal cells and found that det1-2 phot was capable of efficient growth under high light intensities, where wild-type (WT) cells were unable to survive. The mutant exhibited a smaller PSII cross-section in the dark and showed a detachment of the peripheral light-harvesting complex II (LHCII) antenna in the NPQ state, as suggested by a rise in the chlorophyll fluorescence parameter of photochemical quenching in the dark (qPd > 1). Furthermore, fluorescence decay-associated spectra demonstrated a decreased excitation pressure on PSII, with excess energy being directed toward PSI. The amount of LHCSR1, LHCSR3, and PsbS in the mutant correlated with the magnitude of the protective NPQ response. Overall, the study suggests the mechanism by which the overexpression of photoprotective proteins in det1-2 phot brings about an efficient and effective photoprotective response, enabling the mutant to grow and survive under high light intensities that would otherwise be lethal for WT cells.
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Affiliation(s)
- Sam Wilson
- Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Eunchul Kim
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
| | - Asako Ishii
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
| | - Alexander V Ruban
- Department of Biochemistry, School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan.
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Mao R, Zhang H, Bie L, Liu LN, Gao J. Million-atom molecular dynamics simulations reveal the interfacial interactions and assembly of plant PSII-LHCII supercomplex. RSC Adv 2023; 13:6699-6712. [PMID: 36860540 PMCID: PMC9969236 DOI: 10.1039/d2ra08240c] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Accepted: 02/07/2023] [Indexed: 03/02/2023] Open
Abstract
Protein-protein interface interactions dictate efficient excitation energy transfer from light-harvesting antennas to the photosystem II (PSII) core. In this work, we construct a 1.2 million atom-scale model of plant C2S2-type PSII-LHCII supercomplex and perform microsecond-scale molecular dynamics (MD) simulations to explore the interactions and assembly mechanisms of the sizeable PSII-LHCII supercomplex. We optimize the nonbonding interactions of the PSII-LHCII cryo-EM structure using microsecond-scale MD simulations. Binding free energy calculations with component decompositions reveal that hydrophobic interactions predominantly drive antenna-core association and the antenna-antenna interactions are relatively weak. Despite the positive electrostatic interaction energies, hydrogen bonds and salt bridges mainly provide directional or anchoring forces for interface binding. Analysis of the roles of small intrinsic subunits of PSII suggests that LHCII and CP26 first interact with small intrinsic subunits and then bind to the core proteins, whereas CP29 adopts a one-step binding process to the PSII core without the assistance of other factors. Our study provides insights into the molecular underpinnings of the self-organization and regulation of plant PSII-LHCII. It lays the framework for deciphering the general assembly principles of photosynthetic supercomplexes and possibly other macromolecular structures. The finding also has implications for repurposing photosynthetic systems to enhance photosynthesis.
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Affiliation(s)
- Ruichao Mao
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University Wuhan 430070 Hubei China
| | - Han Zhang
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University Wuhan 430070 Hubei China
| | - Lihua Bie
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University Wuhan 430070 Hubei China
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool Liverpool L69 7ZB UK .,Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China Qingdao 266003 China
| | - Jun Gao
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University Wuhan 430070 Hubei China
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Virtanen O, Tyystjärvi E. Plastoquinone pool redox state and control of state transitions in Chlamydomonas reinhardtii in darkness and under illumination. Photosynth Res 2023; 155:59-76. [PMID: 36282464 PMCID: PMC9792418 DOI: 10.1007/s11120-022-00970-3] [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] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
Movement of LHCII between two photosystems has been assumed to be similarly controlled by the redox state of the plastoquinone pool (PQ-pool) in plants and green algae. Here we show that the redox state of the PQ-pool of Chlamydomonas reinhardtii can be determined with HPLC and use this method to compare the light state in C. reinhardtii with the PQ-pool redox state in a number of conditions. The PQ-pool was at least moderately reduced under illumination with all tested types of visible light and oxidation was achieved only with aerobic dark treatment or with far-red light. Although dark incubations and white light forms with spectral distribution favoring one photosystem affected the redox state of PQ-pool differently, they induced similar Stt7-dependent state transitions. Thus, under illumination the dynamics of the PQ-pool and its connection with light state appears more complicated in C. reinhardtii than in plants. We suggest this to stem from the larger number of LHC-units and from less different absorption profiles of the photosystems in C. reinhardtii than in plants. The data demonstrate that the two different control mechanisms required to fulfill the dual function of state transitions in C. reinhardtii in photoprotection and in balancing light utilization are activated via different means.
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Affiliation(s)
- Olli Virtanen
- Department of Life Technologies/Molecular Plant Biology, University of Turku, 20014, Turku, Finland
| | - Esa Tyystjärvi
- Department of Life Technologies/Molecular Plant Biology, University of Turku, 20014, Turku, Finland.
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Pandit A. Structural dynamics of light harvesting proteins, photosynthetic membranes and cells observed with spectral editing solid-state NMR. J Chem Phys 2022; 157:025101. [DOI: 10.1063/5.0094446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photosynthetic light-harvesting complexes have a remarkable capacity to perform robust photo physics at ambient temperatures and in fluctuating environments. Protein conformational dynamics and membrane mobility are processes that contribute to the light-harvesting efficiencies and control photoprotective responses. This short review describes the application of Magic Angle Spinning (MAS) NMR spectroscopy for characterizing the structural dynamics of pigment, protein and thylakoid membrane components related to light harvesting and photoprotection. I will discuss the use of dynamics-based spectral editing solid-state NMR for distinguishing rigid and mobile components and assessing protein, pigment and lipid dynamics on sub-nanosecond to millisecond timescales. Dynamic spectral editing NMR has been applied to investigate Light-Harvesting Complex II (LHCII) protein conformational dynamics inside lipid bilayers and in native membranes. Furthermore, we used the NMR approach to assess thylakoid membrane dynamics. Finally, it is shown that dynamics-based spectral editing NMR, for reducing spectral complexity, by filtering motion-dependent signals, enabled us to follow processes in live photosynthetic cells.
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Rathod MK, Nellaepalli S, Ozawa SI, Kuroda H, Kodama N, Bujaldon S, Wollman FA, Takahashi Y. Assembly Apparatus of Light-Harvesting Complexes: Identification of Alb3.1-cpSRP-LHCP Complexes in the Green Alga Chlamydomonas reinhardtii. Plant Cell Physiol 2022; 63:70-81. [PMID: 34592750 DOI: 10.1093/pcp/pcab146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 09/24/2021] [Accepted: 09/30/2021] [Indexed: 06/13/2023]
Abstract
The unicellular green alga, Chlamydomonas reinhardtii, contains many light-harvesting complexes (LHCs) associating chlorophylls a/b and carotenoids; the major LHCIIs (types I, II, III and IV) and minor light-harvesting complexes, CP26 and CP29, for photosystem II, as well as nine LHCIs (LHCA1-9), for photosystem I. A pale green mutant BF4 exhibited impaired accumulation of LHCs due to deficiency in the Alb3.1 gene, which encodes the insertase involved in insertion, folding and assembly of LHC proteins in the thylakoid membranes. To elucidate the molecular mechanism by which ALB3.1 assists LHC assembly, we complemented BF4 to express ALB3.1 fused with no, single or triple Human influenza hemagglutinin (HA) tag at its C-terminus (cAlb3.1, cAlb3.1-HA or cAlb3.1-3HA). The resulting complemented strains accumulated most LHC proteins comparable to wild-type (WT) levels. The affinity purification of Alb3.1-HA and Alb3.1-3HA preparations showed that ALB3.1 interacts with cpSRP43 and cpSRP54 proteins of the chloroplast signal recognition particle (cpSRP) and several LHC proteins; two major LHCII proteins (types I and III), two minor LHCII proteins (CP26 and CP29) and eight LHCI proteins (LHCA1, 2, 3, 4, 5, 6, 8 and 9). Pulse-chase labeling experiments revealed that the newly synthesized major LHCII proteins were transiently bound to the Alb3.1 complex. We propose that Alb3.1 interacts with cpSRP43 and cpSRP54 to form an assembly apparatus for most LHCs in the thylakoid membranes. Interestingly, photosystem I (PSI) proteins were also detected in the Alb3.1 preparations, suggesting that the integration of LHCIs to a PSI core complex to form a PSI-LHCI subcomplex occurs before assembled LHCIs dissociate from the Alb3.1-cpSRP complex.
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Affiliation(s)
- Mithun Kumar Rathod
- Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530 Japan
| | - Sreedhar Nellaepalli
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Shin-Ichiro Ozawa
- Institute of Plant Science and Resources, Okayama University, Kurashiki, 710-0046 Japan
| | - Hiroshi Kuroda
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Natsumi Kodama
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
| | - Sandrine Bujaldon
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne Université, Paris 75005, France
| | - Francis-André Wollman
- Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne Université, Paris 75005, France
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530 Japan
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Hippler M, Minagawa J, Takahashi Y. Photosynthesis and Chloroplast Regulation-Balancing Photosynthesis and Photoprotection under Changing Environments. Plant Cell Physiol 2021; 62:1059-1062. [PMID: 34528684 DOI: 10.1093/pcp/pcab139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 09/12/2021] [Accepted: 09/15/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Michael Hippler
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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Sperdouli I, Moustaka J, Ouzounidou G, Moustakas M. Leaf Age-Dependent Photosystem II Photochemistry and Oxidative Stress Responses to Drought Stress in Arabidopsis thaliana Are Modulated by Flavonoid Accumulation. Molecules 2021; 26:4157. [PMID: 34299433 DOI: 10.3390/molecules26144157] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/04/2021] [Accepted: 07/06/2021] [Indexed: 11/17/2022] Open
Abstract
We investigated flavonoid accumulation and lipid peroxidation in young leaves (YL) and mature leaves (ML) of Arabidopsis thaliana plants, whose watering stopped 24 h before sampling, characterized as onset of drought stress (OnDS), six days before sampling, characterized as mild drought stress (MiDS), and ten days before sampling, characterized as moderate drought stress (MoDS). The response to drought stress (DS) of photosystem II (PSII) photochemistry, in both leaf types, was evaluated by estimating the allocation of absorbed light to photochemistry (ΦPSII), to heat dissipation by regulated non-photochemical energy loss (ΦNPQ) and to non-regulated energy dissipated in PSII (ΦNO). Young leaves were better protected at MoDS than ML leaves, by having higher concentration of flavonoids that promote acclimation of YL PSII photochemistry to MoDS, showing lower lipid peroxidation and excitation pressure (1 - qp). Young leaves at MoDS possessed lower 1 - qp values and lower excess excitation energy (EXC), not only compared to MoDS ML, but even to MiDS YL. They also possessed a higher capacity to maintain low ΦNO, suggesting a lower singlet oxygen (1O2) generation. Our results highlight that leaves of different developmental stage may display different responses to DS, due to differential accumulation of metabolites, and imply that PSII photochemistry in Arabidopsis thaliana may not show a dose dependent DS response.
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