Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Light energy is converted to chemical energy by two photosystems (PSI and PSII) in complex with their light-harvesting complex proteins (LHCI and LHCII) in photosynthesis. Rhodomonas is a member of cryptophyte alga whose LHCs contain unique chlorophyll a/c proteins (ACPs) and phycobiliproteins. We purified PSI-ACPI and PSII-ACPII supercomplexes from a cryptophyte Rhodomonas sp. NIES-2332 and analyzed their structures at high resolutions of 2.08 Å and 2.17 Å, respectively, using cryo-electron microscopy. These structures are largely similar to those reported previously from two other species of cryptophytes, but exhibited some differences in both the pigment locations and subunit structures. A part of the antenna subunits of both photosystems is shifted compared with the previously reported structures from other species of cryptophytes, suggesting some differences in the energy transfer rates from the antenna to the PSI and PSII cores. Newly identified lipids are found to occupy the interfaces between the antennae and cores, which may be important for assembly and stabilization of the supercomplexes. Water molecules surrounding three iron-sulfur clusters of the PSI core are found in our high-resolution structure, some of which are conserved from cyanobacteria to higher plants but some are different. In addition, our structure of PSII-ACPII lacks the subunits of oxygen-evolving complex as well as the Mn ₄ CaO ₅ cluster, suggesting that the cells are in the S-growth phase, yet the PSI-ACPI structure showed the binding of PsaQ, suggesting that it is in an L-phase. These results suggest that the S-phase and L-phase can co-exist in the cryptophytic cells. The high-resolution structures of both PSI-ACPIs and PSII-ACPIIs solved in this study provide a more solid structural basis for elucidating the energy transfer and quenching mechanisms in this group of the organisms.

DOI： 10.3389/fpls.2025.1716939

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

Haptophytes are unicellular algae that produce 30 to 50% of biomass in oceans. Among haptophytes, a subset named coccolithophores is characterized by calcified scales. Despite the importance of coccolithophores in global carbon fixation and CaCO3 production, their energy conversion system is still poorly known. Here we report a cryo-electron microscopic structure of photosystem II (PSII)-fucoxanthin chlorophyll c-binding protein (FCPII) supercomplex from Chyrostila roscoffensis, a representative of coccolithophores. This complex has two sets of six dimeric and monomeric FCPIIs, with distinct orientations. Interfaces of both FCPII/FCPII and FCPII/core differ from previously reported. We also determine the sequence of Psb36, a subunit previously found in diatoms and red algae. The principal excitation energy transfer (EET) pathways involve mainly 5 FCPIIs, where one FCPII monomer mediates EET to CP47. Our findings provide a solid structural basis for EET and energy dissipation pathways occurring in coccolithophores.

DOI： 10.1038/s41467-025-59512-9

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Coccomyxa subellipsoidea is an oleaginous, non-motile unicellular green microalga isolated from Antarctica, and is an attractive candidate for CO2 fixation and biomass production. C. subellipsoidea is the first polar green alga whose genome has been sequenced. Understanding the structure of photosystems from C. subellipsoidea can provide more information about the conversion of light energy into chemical energy under extreme environments. Photosystems I (PSI) is one of the two photosystems highly conserved from cyanobacteria to vascular plants, and associates with a large amount of outer light-harvesting complex (LHC) which absorb light energy and transfer them to the core complex. Here, we determined the structure of the PSI-10 LHCIs and PSI-8 LHCIs supercomplexes from C. subellipsoidea at 1.92 Å and 2.06 Å resolutions by cryo-electron microscopy, respectively. The supercomplex is similar to PSI-LHCI from other green algae, whereas a large amount of water molecules is observed in our structure because of the high-resolution map. Two novel chlorophylls (Chls), Chl a321 in Lhca4 and Chl a314 in Lhca8, are observed at the lumenal side in our structure, in which Lhca8-Chl a314 provides a potential excitation energy transfer (EET) pathway between the inner-belt of LHCI and the core at the lumenal side. A total of three major EET pathways from LHCIs to PSI core are proposed, and C. subellipsoidea might adapt to the extreme environment by transferring energy in these three different EET pathways instead of by two major pathways proposed in other organisms.

DOI： 10.1016/j.bbabio.2025.149543

PubMed

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Society for Microbiology  

Cumene dioxygenase (CumDO) is an initial enzyme in the cumene degradation pathway of Pseudomonas fluorescens IP01 and is a Rieske non-heme iron oxygenase (RO) that comprises two electron transfer components (reductase [CumDO-R] and Rieske-type ferredoxin [CumDO-F]) and one catalytic component (α3β3-type oxygenase [CumDO-O]). Catalysis is triggered by electrons that are transferred from NAD(P)H to CumDO-O by CumDO-R and CumDO-F. To investigate the binding mode between CumDO-F and CumDO-O and to identify the key CumDO-O amino acid residues for binding, we simulated docking between the CumDO-O crystal structure and predicted model of CumDO-F and identified two potential binding sites: one is at the side-wise site and the other is at the top-wise site in mushroom-like CumDO-O. Then, we performed alanine mutagenesis of 16 surface amino acid residues at two potential binding sites. The results of reduction efficiency analyses using the purified components indicated that CumDO-F bound at the side-wise site of CumDO-O, and K117 of the α-subunit and R65 of the β-subunit were critical for the interaction. Moreover, these two positively charged residues are well conserved in α3β3-type oxygenase components of ROs whose electron donors are Rieske-type ferredoxins. Given that these residues were not conserved if the electron donors were different types of ferredoxins or reductases, the side-wise site of the mushroom-like structure is thought to be the common binding site between Rieske-type ferredoxin and α3β3-type oxygenase components in ROs.

DOI： 10.1128/aem.00835-22

PubMed

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Doctoral thesis  

DOI： 10.15083/0002004915

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J-GLOBAL

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Event date： 2025.9.24 - 2025.9.26

Language：English   Presentation type：Poster presentation  

Venue：Nara  

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Event date： 2025.9.8 - 2025.9.12

Language：English   Presentation type：Oral presentation (general)  

Venue：Qingdao  

Coccomyxa subellipsoidea is an oleaginous, non-motile, unicellular green microalga isolated from Antarctica, and is an attractive candidate for CO2 fixation and biomass production. Understanding the structure of photosystems from C. subellipsoidea may provide valuable insights into how light energy is converted into chemical energy under extreme environmental conditions.
Here we determined the structures of PSI-10 LHCI and PSI-8 LHCI supercomplexes from C. subellipsoidea at 1.92 Å and 2.06 Å resolution, respectively. The structures of these supercomplexes are generally similar to those found in other green algae; however, due to the high-resolution maps, numerous water molecules are clearly resolved in the structures. Comparing the PSI-10 LHCI structure with those from other green algae, two novel chlorophylls (Chls) are found at the lumenal side: Chl a314/Lhca4 located at the outer belt of LHCIs, and Chl a321/Lhca8 located at the interface of the inner belt of LHCIs and PSI core. Notably, Chl a321/Lhca8 provides a novel excitation energy transfer pathway between the inner LHCI-belt and the PsaJ subunit of PSI core at the lumenal side. These two chlorophylls appear to be unique to C. subellipsoidea, as their coordinating amino acid residues are not conserved in other green algae. In addition, we observed a group of water molecules coordinated by Chl a832/PsaB. These water molecules form a connected network to the surface of PSI-LHCI at the stromal side. Although their functional significance remains unknown, similar water networks have been observed in the high-resolution structures of PSI from cyanobacteria to plants, which suggests that this conserved network may play some roles in proton transfer and/or maintaining the structure of PSI at this region.

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Event date： 2025.7.26 - 2025.7.30

Language：English   Presentation type：Poster presentation  

Venue：Milwaukee  

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Event date： 2025.3.14 - 2025.3.16

Language：English   Presentation type：Oral presentation (general)  

Venue：Kanazawa  

Coccomyxa subellipsoidea is an oleaginous non-motile unicellular green microalga isolated from Antarctica, and is an attractive candidate for CO2 fixation and biomass production. Understanding the structure of photosystems from C. subellipsoidea may provide more information about the conversion of light energy into chemical energy under extreme environments. Photosystems I (PSI) core is a natural light-energy converter highly conserved from cyanobacteria to vascular plants, whereas its outer light-harvesting complex (LHC) is largely different among different photosynthetic organisms. Here we determined the structures of PSI-10 LHCI and PSI-8 LHCI supercomplexes from C. subellipsoidea at 1.92 Å and 2.06 Å resolution, respectively. They are similar to the PSI supercomplex from other green algae, but a number of water molecules are visible in the structure because of the high-resolution map. Two novel chlorophylls (Chls) are found at the lumenal side: Chl a314/ Lhca4 and Chl a321/ Lhca8. Among them, the later Chl a provides a novel excitation energy transfer pathway between the inner LHCI-belt and PSI core at the lumenal side.

File： JSPP2025_slides蔡弼丞.pdf

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Event date： 2025.3.4 - 2025.3.8

Language：English   Presentation type：Poster presentation  

Venue：Sapporo  

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Work type：Database science   Location：EMPIAR - Electron Microscopy Public Image Archive  

DOI： 10.6019/EMPIAR-12501

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Work type：Database science   Location：RCSB Protein Data Bank  

DOI： 10.2210/pdb9KQB/pdb

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Work type：Database science   Location：RCSB Protein Data Bank  

DOI： 10.2210/pdb9KQQ/pdb

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Work type：Database science   Location：RCSB Protein Data Bank  

DOI： 10.2210/pdb9KQP

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Audience： College students,　Graduate students,　Researchesrs,　General

Type：Lecture

File： (4_3)2025第三屆JTBA年會-宣傳海報(草稿)_20251112.png

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Audience： Graduate students,　Researchesrs,　General

Type：Seminar, workshop

File： btba-jtba-e4baa4e6b581e69c83-jtba.jpg

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Audience： College students,　Graduate students,　Researchesrs,　General

Type：Lecture

File： (更新版) 年會海報.png

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Audience： College students,　Graduate students,　Researchesrs,　General

Type：Lecture

File： 第二波宣傳_海報 (講者更改+協贊單位).png

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Type：Academic society, research group, etc. 

File： WS.png

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