Faculty Profiles - SHEN Jian-Ren

Papers - SHEN Jian-Ren

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Architecture of the chloroplast PSI-NDH supercomplex in Hordeum vulgare. Reviewed International journal

Liangliang Shen, Kailu Tang, Wenda Wang, Chen Wang, Hangjun Wu, Zhiyuan Mao, Shaoya An, Shenghai Chang, Tingyun Kuang, Jian-Ren Shen, Guangye Han, Xing Zhang

Nature 2021.12

Language：English Publishing type：Research paper (scientific journal)

The chloroplast NADH dehydrogenase-like (NDH) complex is composed of at least 29 subunits and has an important role in mediating photosystem I (PSI) cyclic electron transport (CET)1-3. The NDH complex associates with PSI to form the PSI-NDH supercomplex and fulfil its function. Here, we report cryo-electron microscopy structures of a PSI-NDH supercomplex from barley (Hordeum vulgare). The structures reveal that PSI-NDH is composed of two copies of the PSI-light-harvesting complex I (LHCI) subcomplex and one NDH complex. Two monomeric LHCI proteins, Lhca5 and Lhca6, mediate the binding of two PSI complexes to NDH. Ten plant chloroplast-specific NDH subunits are presented and their exact positions as well as their interactions with other subunits in NDH are elucidated. In all, this study provides a structural basis for further investigations on the functions and regulation of PSI-NDH-dependent CET.

DOI： 10.1038/s41586-021-04277-6

Structural basis for high selectivity of a rice silicon channel Lsi1 Reviewed

Yasunori Saitoh, Namiki Mitani-Ueno, Keisuke Saito, Kengo Matsuki, Sheng Huang, Lingli Yang, Naoki Yamaji, Hiroshi Ishikita, Jian-Ren Shen, Jian Feng Ma, Michihiro Suga

Nature Communications 12 ( 1 ) 2021.12

Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

<title>Abstract</title>Silicon (Si), the most abundant mineral element in the earth’s crust, is taken up by plant roots in the form of silicic acid through Low silicon rice 1 (Lsi1). Lsi1 belongs to the Nodulin 26-like intrinsic protein subfamily in aquaporin and shows high selectivity for silicic acid. To uncover the structural basis for this high selectivity, here we show the crystal structure of the rice Lsi1 at a resolution of 1.8 Å. The structure reveals transmembrane helical orientations different from other aquaporins, characterized by a unique, widely opened, and hydrophilic selectivity filter (SF) composed of five residues. Our structural, functional, and theoretical investigations provide a solid structural basis for the Si uptake mechanism in plants, which will contribute to secure and sustainable rice production by manipulating Lsi1 selectivity for different metalloids.

DOI： 10.1038/s41467-021-26535-x

Other Link： https://www.nature.com/articles/s41467-021-26535-x

Molecular phylogeny of fucoxanthin‐chlorophyll a / c proteins from Chaetoceros gracilis and Lhcq/Lhcf diversity Reviewed

Minoru Kumazawa, Hiroyo Nishide, Ryo Nagao, Natsuko Inoue‐Kashino, Jian‐Ren Shen, Takeshi Nakano, Ikuo Uchiyama, Yasuhiro Kashino, Kentaro Ifuku

Physiologia Plantarum 174 ( 1 ) 2021.11

Excitation-energy transfer in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120 as studied by time-resolved fluorescence spectroscopy. Reviewed International journal

Ryo Nagao, Makio Yokono, Yoshifumi Ueno, Yoshiki Nakajima, Takehiro Suzuki, Ka-Ho Kato, Naoki Tsuboshita, Naoshi Dohmae, Jian-Ren Shen, Shigeki Ehira, Seiji Akimoto

Biochimica et biophysica acta. Bioenergetics 1863 ( 1 ) 148509 - 148509 2021.11

Language：English Publishing type：Research paper (scientific journal)

Heterocysts are formed in filamentous heterocystous cyanobacteria under nitrogen-starvation conditions, and possess a very low amount of photosystem II (PSII) complexes than vegetative cells. Molecular, morphological, and biochemical characterizations of heterocysts have been investigated; however, excitation-energy dynamics in heterocysts are still unknown. In this study, we examined excitation-energy-relaxation processes of pigment-protein complexes in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120. Thylakoid membranes from the heterocysts showed no oxygen-evolving activity under our experimental conditions and no thermoluminescence-glow curve originating from charge recombination of S2QA-. Two dimensional blue-native/SDS-PAGE analysis exhibits tetrameric, dimeric, and monomeric photosystem I (PSI) complexes but almost no dimeric and monomeric PSII complexes in the heterocyst thylakoids. The steady-state fluorescence spectrum of the heterocyst thylakoids at 77 K displays both characteristic PSI fluorescence and unusual PSII fluorescence different from the fluorescence of PSII dimer and monomer complexes. Time-resolved fluorescence spectra at 77 K, followed by fluorescence decay-associated spectra, showed different PSII and PSI fluorescence bands between heterocysts and vegetative thylakoids. Based on these findings, we discuss excitation-energy-transfer mechanisms in the heterocysts.

DOI： 10.1016/j.bbabio.2021.148509

The importance of identifying the true catalyst when using Randles-Sevcik equation to calculate turnover frequency Reviewed

Zahra Abdi, Matthias Vandichel, Alla S. Sologubenko, Marc-Georg Willinger, Jian-Ren Shen, Suleyman I. Allakhverdiev, Mohammad Mahdi Najafpour

International Journal of Hydrogen Energy 46 ( 76 ) 37774 - 37781 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

Water splitting will become important to store excess renewable electrical energy into hydrogen. Although the oxygen-evolution reaction (OER) by water oxidation is a critical reaction for water splitting, further investigations are needed to find the details of the OER mechanism for various electrocatalysts. More in particular for homogeneous electrocatalysts, the Randles-Sevcik equation has been extensively applied to determine the turnover frequency (TOF). Herein, using vitamin B12 as a case study, we show that the dynamical deposition/dissolution of the heterogeneous catalyst during OER makes the Randles-Sevcik equation too complicated to be used for calculating the TOF. Indeed, the conventionally applied post-characterization methods do not provide sufficient accuracy to prove the homogeneity of OER mechanisms
thus, using the Randles-Sevcik equation to calculate the TOF is not necessarily correct.

DOI： 10.1016/j.ijhydene.2021.09.039

Cryo-EM structure of monomeric photosystem II at 2.78 Å resolution reveals factors important for the formation of dimer. Reviewed International journal

Huaxin Yu, Tasuku Hamaguchi, Yoshiki Nakajima, Koji Kato, Keisuke Kawakami, Fusamichi Akita, Koji Yonekura, Jian-Ren Shen

Biochimica et biophysica acta. Bioenergetics 1862 ( 10 ) 148471 - 148471 2021.10

Language：English Publishing type：Research paper (scientific journal)

Photosystem II (PSII) functions mainly as a dimer to catalyze the light energy conversion and water oxidation reactions. However, monomeric PSII also exists and functions in vivo in some cases. The crystal structure of monomeric PSII has been solved at 3.6 Å resolution, but it is still not clear which factors contribute to the formation of the dimer. Here, we solved the structure of PSII monomer at a resolution of 2.78 Å using cryo-electron microscopy (cryo-EM). From our cryo-EM density map, we observed apparent differences in pigments and lipids in the monomer-monomer interface between the PSII monomer and dimer. One β-carotene and two sulfoquinovosyl diacylglycerol (SQDG) molecules are found in the monomer-monomer interface of the dimer structure but not in the present monomer structure, although some SQDG and other lipid molecules are found in the analogous region of the low-resolution crystal structure of the monomer, or cryo-EM structure of an apo-PSII monomer lacking the extrinsic proteins from Synechocystis sp. PCC 6803. In the current monomer structure, a large part of the PsbO subunit was also found to be disordered. These results indicate the importance of the β-carotene, SQDG and PsbO in formation of the PSII dimer.

DOI： 10.1016/j.bbabio.2021.148471

Structural basis for the absence of low-energy chlorophylls responsible for photoprotection from a primitive cyanobacterial PSI

Koji Kato, Tasuku Hamaguchi, Ryo Nagao, Keisuke Kawakami, Yoshifumi Ueno, Takehiro Suzuki, Hiroko Uchida, Akio Murakami, Yoshiki Nakajima, Makio Yokono, Seiji Akimoto, Naoshi Dohmae, Koji Yonekura, Jian-Ren Shen

2021.10

Publisher：Cold Spring Harbor Laboratory

Abstract

Photosystem I (PSI) of photosynthetic organisms is a multi-subunit pigment-protein complex and functions in light harvesting and photochemical charge-separation reactions, followed by reduction of NADP to NADPH required for CO₂ fixation. PSI from different photosynthetic organisms has a variety of chlorophylls (Chls), some of which are at lower-energy levels than its reaction center P700, a special pair of Chls, and are called low-energy Chls. However, the site of low-energy Chls is still under debate. Here, we solved a 2.04-Å resolution structure of a PSI trimer by cryo-electron microscopy from a primitive cyanobacterium Gloeobacter violaceus PCC 7421, which has no low-energy Chls. The structure showed absence of some subunits commonly found in other cyanobacteria, confirming the primitive nature of this cyanobacterium. Comparison with the known structures of PSI from other cyanobacteria and eukaryotic organisms reveals that one dimeric and one trimeric Chls are lacking in the Gloeobacter PSI. The dimeric and trimeric Chls are named Low1 and Low2, respectively. Low2 does not exist in some cyanobacterial and eukaryotic PSIs, whereas Low1 is absent only in Gloeobacter. Since Gloeobacter is susceptible to light, this indicates that Low1 serves as a main photoprotection site in most oxyphototrophs, whereas Low2 is involved in either energy transfer or energy quenching in some of the oxyphototrophs. Thus, these findings provide insights into not only the functional significance of low-energy Chls in PSI, but also the evolutionary changes of low-energy Chls responsible for the photoprotection machinery from photosynthetic prokaryotes to eukaryotes.

DOI： 10.1101/2021.09.29.462462

Structural implications for a phycobilisome complex from the thermophilic cyanobacterium Thermosynechococcus vulcanus. Reviewed International journal

Keisuke Kawakami, Ryo Nagao, Yuhei O Tahara, Tasuku Hamaguchi, Takehiro Suzuki, Naoshi Dohmae, Daisuke Kosumi, Jian-Ren Shen, Makoto Miyata, Koji Yonekura, Nobuo Kamiya

Biochimica et biophysica acta. Bioenergetics 1862 ( 9 ) 148458 - 148458 2021.9

Language：English Publishing type：Research paper (scientific journal)

Phycobilisomes (PBSs) are huge, water-soluble light-harvesting complexes used by oxygenic photosynthetic organisms. The structures of some subunits of the PBSs, including allophycocyanin (APC) and phycocyanin (PC), have been solved by X-ray crystallography previously. However, there are few reports on the overall structures of PBS complexes in photosynthetic organisms. Here, we report the overall structure of the PBS complex isolated from the cyanobacterium Thermosynechococcus vulcanus, determined by negative-staining electron microscopy (EM). Intact PBS complexes were purified by trehalose density gradient centrifugation with a high-concentration phosphate buffer and then subjected to a gradient-fixation preparation using glutaraldehyde. The final map constructed by the single-particle analysis of EM images showed a hemidiscoidal structure of the PBS, consisting of APC cores and peripheral PC rods. The APC cores are composed of five cylinders: A1, A2, B, C1, and C2. Each of the cylinders is composed of three (A1 and A2), four (B), or two (C1 and C2) APC trimers. In addition, there are eight PC rods in the PBS: one bottom pair (Rb and Rb'), one top pair (Rt and Rt'), and two side pairs (Rs1/Rs1' and Rs2/Rs2'). Comparison with the overall structures of PBSs from other organisms revealed structural characteristics of T. vulcanus PBS.

DOI： 10.1016/j.bbabio.2021.148458

Structural insights into cyanobacterial photosystem II intermediates associated with Psb28 and Tsl0063. Reviewed International journal

Yanan Xiao, Guoqiang Huang, Xin You, Qingjun Zhu, Wenda Wang, Tingyun Kuang, Guangye Han, Sen-Fang Sui, Jian-Ren Shen

Nature plants 7 ( 8 ) 1132 - 1142 2021.8

Language：English Publishing type：Research paper (scientific journal)

Photosystem II (PSII) is a multisubunit pigment-protein complex and catalyses light-induced water oxidation, leading to the conversion of light energy into chemical energy and the release of dioxygen. We analysed the structures of two Psb28-bound PSII intermediates, Psb28-RC47 and Psb28-PSII, purified from a psbV-deletion strain of the thermophilic cyanobacterium Thermosynechococcus vulcanus, using cryo-electron microscopy. Both Psb28-RC47 and Psb28-PSII bind one Psb28, one Tsl0063 and an unknown subunit. Psb28 is located at the cytoplasmic surface of PSII and interacts with D1, D2 and CP47, whereas Tsl0063 is a transmembrane subunit and binds at the side of CP47/PsbH. Substantial structural perturbations are observed at the acceptor side, which result in conformational changes of the quinone (QB) and non-haem iron binding sites and thus may protect PSII from photodamage during assembly. These results provide a solid structural basis for understanding the assembly process of native PSII.

DOI： 10.1038/s41477-021-00961-7

High-light modification of excitation-energy-relaxation processes in the green flagellate Euglena gracilis. Reviewed International journal

Ryo Nagao, Makio Yokono, Ka-Ho Kato, Yoshifumi Ueno, Jian-Ren Shen, Seiji Akimoto

Photosynthesis research 149 ( 3 ) 303 - 311 2021.5

Language：English Publishing type：Research paper (scientific journal)

Photosynthetic organisms finely tune their photosynthetic machinery including pigment compositions and antenna systems to adapt to various light environments. However, it is poorly understood how the photosynthetic machinery in the green flagellate Euglena gracilis is modified under high-light conditions. In this study, we examined high-light modification of excitation-energy-relaxation processes in Euglena cells. Oxygen-evolving activity in the cells incubated at 300 µmol photons m-2 s-1 (HL cells) cannot be detected, reflecting severe photodamage to photosystem II (PSII) in vivo. Pigment compositions in the HL cells showed relative increases in 9'-cis-neoxanthin, diadinoxanthin, and chlorophyll b compared with the cells incubated at 30 µmol photons m-2 s-1 (LL cells). Absolute fluorescence spectra at 77 K exhibit smaller intensities of the PSII and photosystem I (PSI) fluorescence in the HL cells than in the LL cells. Absolute fluorescence decay-associated spectra at 77 K of the HL cells indicate suppression of excitation-energy transfer from light-harvesting complexes (LHCs) to both PSI and PSII with the time constant of 40 ps. Rapid energy quenching in LHCs and PSII in the HL cells is distinctly observed by averaged Chl-fluorescence lifetimes. These findings suggest that Euglena modifies excitation-energy-relaxation processes in addition to pigment compositions to deal with excess energy. These results provide insights into the photoprotection strategies of this alga under high-light conditions.

DOI： 10.1007/s11120-021-00849-9

A unique photosystem I reaction center from a chlorophyll d-containing cyanobacterium Acaryochloris marina. Reviewed International journal

Caihuang Xu, Qingjun Zhu, Jing-Hua Chen, Liangliang Shen, Xiaohan Yi, Zihui Huang, Wenda Wang, Min Chen, Tingyun Kuang, Jian-Ren Shen, Xing Zhang, Guangye Han

Journal of integrative plant biology 2021.5

Language：English Publishing type：Research paper (scientific journal)

Photosystem I (PSI) is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin (or cytochrome c6 ) and the reduction of ferredoxin. This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor (a special chlorophyll (Chl) pair) and electron acceptors A0 , A1 , and three Fe4 S4 clusters, FX , FA , and FB . Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3 Å resolution obtained by single-particle cryo-electron microscopy. The A. marina PSI exists as a trimer with three identical monomers. Surprisingly, the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A0 is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures. A novel subunit Psa27 is observed in the A. marina PSI structure. In addition, 77 Chls, 13 α-carotenes, two phylloquinones, three Fe-S clusters, two phosphatidyl glycerols, and one monogalactosyl-diglyceride were identified in each PSI monomer. Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.

DOI： 10.1111/jipb.13113

Capturing structural changes of the S1 to S2 transition of photosystem II using time-resolved serial femtosecond crystallography. Reviewed International journal

Hongjie Li, Yoshiki Nakajima, Takashi Nomura, Michihiro Sugahara, Shinichiro Yonekura, Siu Kit Chan, Takanori Nakane, Takahiro Yamane, Yasufumi Umena, Mamoru Suzuki, Tetsuya Masuda, Taiki Motomura, Hisashi Naitow, Yoshinori Matsuura, Tetsunari Kimura, Kensuke Tono, Shigeki Owada, Yasumasa Joti, Rie Tanaka, Eriko Nango, Fusamichi Akita, Minoru Kubo, So Iwata, Jian-Ren Shen, Michihiro Suga

IUCrJ 8 ( Pt 3 ) 431 - 443 2021.5

Language：English Publishing type：Research paper (scientific journal)

Photosystem II (PSII) catalyzes light-induced water oxidation through an S
i
-state cycle, leading to the generation of di-oxygen, protons and electrons. Pump-probe time-resolved serial femtosecond crystallography (TR-SFX) has been used to capture structural dynamics of light-sensitive proteins. In this approach, it is crucial to avoid light contamination in the samples when analyzing a particular reaction intermediate. Here, a method for determining a condition that avoids light contamination of the PSII microcrystals while minimizing sample consumption in TR-SFX is described. By swapping the pump and probe pulses with a very short delay between them, the structural changes that occur during the S1-to-S2 transition were examined and a boundary of the excitation region was accurately determined. With the sample flow rate and concomitant illumination conditions determined, the S2-state structure of PSII could be analyzed at room temperature, revealing the structural changes that occur during the S1-to-S2 transition at ambient temperature. Though the structure of the manganese cluster was similar to previous studies, the behaviors of the water molecules in the two channels (O1 and O4 channels) were found to be different. By comparing with the previous studies performed at low temperature or with a different delay time, the possible channels for water inlet and structural changes important for the water-splitting reaction were revealed.

DOI： 10.1107/S2052252521002177

Structure of plant photosystem I-light harvesting complex I supercomplex at 2.4 Å resolution. Reviewed International journal

Jie Wang, Long-Jiang Yu, Wenda Wang, Qiujing Yan, Tingyun Kuang, Xiaochun Qin, Jian-Ren Shen

Journal of integrative plant biology 2021.3

Language：English Publishing type：Research paper (scientific journal)

Photosystem I (PSI) is one of the two photosystems in photosynthesis, and performs a series of electron transfer reactions leading to the reduction of ferredoxin. In higher plants, PSI is surrounded by four light-harvesting complex I (LHCI) subunits, which harvest and transfer energy efficiently to the PSI core. The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6 Å resolution, providing much information on the arrangement of proteins and cofactors in this complicated supercomplex. Here we have optimized crystallization conditions, and analyzed the crystal structure of PSI-LHCI at 2.4 Å resolution. Our structure showed some shift of the LHCI, especially the Lhca4 subunit, away from the PSI core, suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core. We identified five new lipids in the structure, most of them are located in the gap region between the Lhca subunits and the PSI core. These lipid molecules may play important roles in binding of the Lhca subunits to the core, as well as in the assembly of the supercomplex. The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting, transfer and assembly of this supercomplex. This article is protected by copyright. All rights reserved.

DOI： 10.1111/jipb.13095

High-resolution cryo-EM structure of photosystem II reveals damage from high-dose electron beams Reviewed International journal

Koji Kato, Naoyuki Miyazaki, Tasuku Hamaguchi, Yoshiki Nakajima, Fusamichi Akita, Koji Yonekura, Jian-Ren Shen

COMMUNICATIONS BIOLOGY 4 ( 1 ) 382 - 382 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE RESEARCH

Photosystem II (PSII) plays a key role in water-splitting and oxygen evolution. X-ray crystallography has revealed its atomic structure and some intermediate structures. However, these structures are in the crystalline state and its final state structure has not been solved. Here we analyzed the structure of PSII in solution at 1.95 angstrom resolution by single-particle cryo-electron microscopy (cryo-EM). The structure obtained is similar to the crystal structure, but a PsbY subunit was visible in the cryo-EM structure, indicating that it represents its physiological state more closely. Electron beam damage was observed at a high-dose in the regions that were easily affected by redox states, and reducing the beam dosage by reducing frames from 50 to 2 yielded a similar resolution but reduced the damage remarkably. This study will serve as a good indicator for determining damage-free cryo-EM structures of not only PSII but also all biological samples, especially redox-active metalloproteins. Kato, Miyazaki, Hamaguchi et al. report the structure of Photosystem II in solution at 1.95 angstrom resolution by single-particle cryo-electron microscopy. They find that reducing the electron beam dosage decreases the electron beam damage while keeping the resolution of the cryo-EM structure, providing insights into the best practice for the determination of cryo-EM structures.

DOI： 10.1038/s42003-021-01919-3

Structure of photosystem I-LHCI-LHCII from the green alga Chlamydomonas reinhardtii in State 2 Reviewed International journal

Zihui Huang, Liangliang Shen, Wenda Wang, Zhiyuan Mao, Xiaohan Yi, Tingyun Kuang, Jian-Ren Shen, Xing Zhang, Guangye Han

NATURE COMMUNICATIONS 12 ( 1 ) 1100 - 1100 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE RESEARCH

Photosystem I (PSI) and II (PSII) balance their light energy distribution absorbed by their light-harvesting complexes (LHCs) through state transition to maintain the maximum photosynthetic performance and to avoid photodamage. In state 2, a part of LHCII moves to PSI, forming a PSI-LHCI-LHCII supercomplex. The green alga Chlamydomonas reinhardtii exhibits state transition to a far larger extent than higher plants. Here we report the cryo-electron microscopy structure of a PSI-LHCI-LHCII supercomplex in state 2 from C. reinhardtii at 3.42 angstrom resolution. The result reveals that the PSI-LHCI-LHCII of C. reinhardtii binds two LHCII trimers in addition to ten LHCI subunits. The PSI core subunits PsaO and PsaH, which were missed or not well-resolved in previous Cr-PSI-LHCI structures, are observed. The present results reveal the organization and assembly of PSI core subunits, LHCI and LHCII, pigment arrangement, and possible pathways of energy transfer from peripheral antennae to the PSI core. Photosystems (PS) I and II undergo state transitions to optimize photosynthesis and photoprotection. Here the authors report a cryo-electron microscopy structure of the state 2 PSI-LHCI-LHCII supercomplex from C. reinhardtii revealing subunit organization and possible pathways of energy transfer.

DOI： 10.1038/s41467-021-21362-6

Structural insights into a dimeric Psb27-photosystem II complex from a cyanobacterium Thermosynechococcus vulcanus Reviewed International journal

Guoqiang Huang, Yanan Xiao, Xiong Pi, Liang Zhao, Qingjun Zhu, Wenda Wang, Tingyun Kuang, Guangye Han, Sen-Fang Sui, Jian-Ren Shen

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 118 ( 5 ) 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：NATL ACAD SCIENCES

Photosystem II (PSII) is a multisubunit pigment-protein complex and catalyzes light-driven water oxidation, leading to the conversion of light energy into chemical energy and the release of molecular oxygen. Psb27 is a small thylakoid lumen-localized protein known to serve as an assembly factor for the biogenesis and repair of the PSII complex. The exact location and binding fashion of Psb27 in the intermediate PSII remain elusive. Here, we report the structure of a dimeric Psb27-PSII complex purified from a psbV deletion mutant (Delta PsbV) of the cyanobacterium Thermosynechococcus vulcanus, solved by cryo-electron microscopy. Our structure showed that Psb27 is associated with CP43 at the luminal side, with specific interactions formed between Helix 2 and Helix 3 of Psb27 and a loop region between Helix 3 and Helix 4 of CP43 (loop C) as well as the large, lumen-exposed and hydrophilic E-loop of CP43. The binding of Psb27 imposes some conflicts with the N-terminal region of PsbO and also induces some conformational changes in CP43, CP47, and D2. This makes PsbO unable to bind in the Psb27-PSII. Conformational changes also occurred in D1, PsbE, PsbF, and PsbZ; this, together with the conformational changes occurred in CP43, CP47, and D2, may prevent the binding of PsbU and induce dissociation of PsbJ. This structural information provides important insights into the regulation mechanism of Psb27 in the biogenesis and repair of PSII.

DOI： 10.1073/pnas.2018053118

Antenna arrangement and energy-transfer pathways of PSI-LHCI from the moss Physcomitrella patens Reviewed International journal

Qiujing Yan, Liang Zhao, Wenda Wang, Xiong Pi, Guangye Han, Jie Wang, Lingpeng Cheng, Yi-Kun He, Tingyun Kuang, Xiaochun Qin, Sen-Fang Sui, Jian-Ren Shen

CELL DISCOVERY 7 ( 1 ) 10 - 10 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGERNATURE

Plants harvest light energy utilized for photosynthesis by light-harvesting complex I and II (LHCI and LHCII) surrounding photosystem I and II (PSI and PSII), respectively. During the evolution of green plants, moss is at an evolutionarily intermediate position from aquatic photosynthetic organisms to land plants, being the first photosynthetic organisms that landed. Here, we report the structure of the PSI-LHCI supercomplex from the moss Physcomitrella patens (Pp) at 3.23 angstrom resolution solved by cryo-electron microscopy. Our structure revealed that four Lhca subunits are associated with the PSI core in an order of Lhca1-Lhca5-Lhca2-Lhca3. This number is much decreased from 8 to 10, the number of subunits in most green algal PSI-LHCI, but the same as those of land plants. Although Pp PSI-LHCI has a similar structure as PSI-LHCI of land plants, it has Lhca5, instead of Lhca4, in the second position of Lhca, and several differences were found in the arrangement of chlorophylls among green algal, moss, and land plant PSI-LHCI. One chlorophyll, PsaF-Chl 305, which is found in the moss PSI-LHCI, is located at the gap region between the two middle Lhca subunits and the PSI core, and therefore may make the excitation energy transfer from LHCI to the core more efficient than that of land plants. On the other hand, energy-transfer paths at the two side Lhca subunits are relatively conserved. These results provide a structural basis for unravelling the mechanisms of light-energy harvesting and transfer in the moss PSI-LHCI, as well as important clues on the changes of PSI-LHCI after landing.

DOI： 10.1038/s41421-021-00242-9

Enhancement of excitation-energy quenching in fucoxanthin chlorophyll alpha/c-binding proteins isolated from a diatom Phaeodactylum tricornutum upon excess-light illumination Reviewed International journal

Ryo Nagao, Makio Yokono, Yoshifumi Ueno, Takehiro Suzuki, Minoru Kumazawa, Ka-Ho Kato, Naoki Tsuboshita, Naoshi Dohmae, Kentaro Ifuku, Jian-Ren Shen, Seiji Akimoto

BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1862 ( 2 ) 148350 - 148350 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER

Photosynthetic organisms regulate pigment composition and molecular oligomerization of light-harvesting complexes in response to solar light intensities, in order to improve light-harvesting efficiency. Here we report excitation-energy dynamics and relaxation of fucoxanthin chlorophyll alpha/c-binding protein (FCP) complexes isolated from a diatom Phaeodactylum tricornutum grown under high-light (HL) illumination. Two types of FCP complexes were prepared from this diatom under the HL condition, whereas one FCP complex was isolated from the cells grown under a low-light (LL) condition. The subunit composition and oligomeric states of FCP complexes under the HL condition are different from those under the LL condition. Absorption and fluorescence spectra at 77 K of the FCP complexes also vary between the two conditions, indicating modifications of the pigment composition and arrangement upon the HL illumination. Time-resolved fluorescence curves at 77 K of the FCP complexes under the HL condition showed shorter lifetime components compared with the LL condition. Fluorescence decay-associated spectra at 77 K showed distinct excitation-energy-quenching components and alterations of energy-transfer pathways in the FCP complexes under the HL condition. These findings provide insights into molecular and functional mechanisms of the dynamic regulation of FCPs in this diatom under excess-light conditions.

DOI： 10.1016/j.bbabio.2020.148350

An Exciton Dynamics Model of Bryopsis corticulans Light-Harvesting Complex II Reviewed International journal

Hoang Long Nguyen, Thanh Nhut Do, Parveen Akhtar, Thomas L. C. Jansen, Jasper Knoester, Wenda Wang, Jian-Ren Shen, Petar H. Lambrev, Howe-Siang Tan

JOURNAL OF PHYSICAL CHEMISTRY B 125 ( 4 ) 1134 - 1143 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Bryopsis corticulans is a marine green macroalga adapted to the intertidal environment. It possesses siphonaxanthin-binding light-harvesting complexes of photosystem II (LHCII) with spectroscopic properties markedly different from the LHCII in plants. By applying a phenomenological fitting procedure to the two-dimensional electronic spectra of the LHCII from B. corticulans measured at 77 K, we can extract information about the excitonic states and energy-transfer processes. The fitting method results in well-converged parameters, including excitonic energy levels with their respective transition dipole moments, spectral widths, energy-transfer rates, and coupling properties. The 2D spectra simulated from the fitted parameters concur very well with the experimental data, showing the robustness of the fitting method. An excitonic energy-transfer scheme can be constructed from the fitting parameters. It shows the rapid energy transfer from chlorophylls (Chls) b to a at subpicosecond time scales and a long-lived state in the Chl b region at around 659 nm. Three weakly connected terminal states are resolved at 671, 675, and 677 nm. The lowest state is higher in energy than that in plant LHCII, which is probably because of the fewer number of Chls a in a B. corticulans LHCII monomer. Modeling based on existing Hamiltonians for the plant LHCII structure with two Chls a switched to Chls b suggests several possible Chl a-b replacements in comparison with those of plant LHCII. The adaptive changes result in a slower energy equilibration in the complex, revealed by the longer relaxation times of several exciton states compared to those of plant LHCII. The strength of our phenomenological fitting method for obtaining excitonic energy levels and energy-transfer network is put to the test in systems such as B. corticulans LHCII, where prior knowledge on exact assignment and spatial locations of pigments are lacking.

DOI： 10.1021/acs.jpcb.0c10634

Light-Adapted Charge-Separated State of Photosystem II: Structural and Functional Dynamics of the Closed Reaction Center. Reviewed International journal

Gábor Sipka, Melinda Magyar, Alberto Mezzetti, Parveen Akhtar, Qingjun Zhu, Yanan Xiao, Guangye Han, Stefano Santabarbara, Jian-Ren Shen, Petar H Lambrev, Győző Garab

The Plant cell 2021.1

Language：English Publishing type：Research paper (scientific journal)

Photosystem II (PSII) uses solar energy to oxidize water and delivers electrons for life on Earth. The photochemical reaction center of PSII is known to possess two stationary states. In the open state (PSIIO), the absorption of a single photon triggers electron-transfer steps, which convert PSII into the charge-separated closed state (PSIIC). Here, by using steady-state and time-resolved spectroscopic techniques on Spinacia oleracea and Thermosynechococcus vulcanus preparations, we show that additional illumination gradually transforms PSIIC into a light-adapted charge-separated state (PSIIL). The PSIIC-to-PSIIL transition, observed at all temperatures between 80 and 308 K, is responsible for a large part of the variable chlorophyll-a fluorescence (Fv) and is associated with subtle, dark-reversible reorganizations in the core complexes, protein conformational changes at non-cryogenic temperatures and marked variations in the rates of photochemical and photophysical reactions. The build-up of PSIIL requires a series of light-induced events generating rapidly recombining primary radical pairs, spaced by sufficient waiting times between these events - pointing to the roles of local electric-field transients and dielectric relaxation processes. We show that the maximum fluorescence level, Fm, is associated with PSIIL rather than with PSIIC, and thus the Fv/Fm parameter cannot be equated with the quantum efficiency of PSII photochemistry. Our findings resolve the controversies and explain the peculiar features of chlorophyll-a fluorescence kinetics, a tool to monitor the functional activity and the structural-functional plasticity of PSII in different wild-type and mutant organisms and under stress conditions.

DOI： 10.1093/plcell/koab008

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