業績情報

• Production of extracellular superoxide contributes to photosynthesis via elimination of reducing power and regeneration of NADP+ in the red-tide-forming raphidophyte Chattonella marina complex　　　　　　　　　　　　　　　
  Koki Yuasa; Takayoshi Ichikawa; Yuma Ishikawa; Haruhiko Jimbo; Maki Kawai-Yamada; Tomoyuki Shikata; Yoshitaka Nishiyama
  Harmful Algae, 巻：139, 開始ページ：102712, 終了ページ：102712, 2024年11月, ［査読有り］
  Elsevier BV, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.hal.2024.102712
  DOI ID：10.1016/j.hal.2024.102712, ISSN：1568-9883
• Acyl‐turnover of acylplastoquinol enhances recovery of photodamaged PSII in Synechocystis
  Haruhiko Jimbo; Mana Torii; Yuichiro Fujino; Yoshiki Tanase; Kazuki Kurima; Naoki Sato; Hajime Wada
  The Plant Journal, 2024年10月, ［査読有り］, ［筆頭著者, 責任著者］
  SUMMARY
  
  Photosynthetic electron transport is carried out by the electron carrier, plastoquinone (PQ). Recently, another form of PQ, acylplastoquinol (APQ), was discovered in Synechocystis sp. PCC 6803 (Synechocystis), but its physiological function in photosynthesis is unclear. In the present study, we identified a lipase encoded in sll0482 gene in Synechocystis that deacylates APQ and releases a free fatty acid and a reduced PQ (plastoquinol, PQH₂), which we named acylplastoquinol lipase (APL). Disruption of apl gene increased APQ content, and recovery of photodamaged PSII under low light (LL) after the exposure to very high light (vHL) at 2500 μmol photons m⁻² sec⁻¹ without aeration (vHL) for 60 min, was suppressed in the Δapl cells. Δapl cells also show the slow rate of de novo synthesis of D1, a reaction center of PSII under such condition. Under high light, the cellular growth of Δapl was inhibited; however, disruption of apl gene did not affect the photosynthetic activity or photoinhibition of PSII. In wild‐type cells, APQ content increased under vHL condition. Also, APQ was converted to PQH₂ after transfer to LL with aeration by ambient air. Such striking changes in APQ were not observed in Δapl cells. The deacylation of APQ by APL may help repair PSII when PSII cannot drive photosynthetic electron transport efficiently.
  Wiley, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1111/tpj.17051
  DOI ID：10.1111/tpj.17051, ISSN：0960-7412, eISSN：1365-313X
• Magic in the Bacterial Genome: Shuffling the Genome for N2-Fixation　　　　　　　　　　　　　　　
  Haruhiko Jimbo
  Plant And Cell Physiology, 2024年06月, ［筆頭著者, 責任著者］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/pcp/pcae052
  DOI ID：10.1093/pcp/pcae052, ORCID：159538252
• High Myristic Acid in Glycerolipids Enhances the Repair of Photodamaged Photosystem II under Strong Light　　　　　　　　　　　　　　　
  Kazuki Kurima; Haruhiko Jimbo; Takashi Fujihara; Masakazu Saito; Toshiki Ishikawa; Hajime Wada
  Plant And Cell Physiology, 2024年05月, ［査読有り］, ［責任著者］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/pcp/pcae021
  DOI ID：10.1093/pcp/pcae021, ORCID：157338608
• Biosynthesis of phosphatidylglycerol in photosynthetic organisms.　　　　　　　　　　　　　　　
  Koichi Kobayashi; Haruhiko Jimbo; Yuki Nakamura; Hajime Wada
  Progress in lipid research, 巻：93, 開始ページ：101266, 終了ページ：101266, 2024年01月, ［査読有り］, ［国際誌］
  Phosphatidylglycerol (PG) is a unique phospholipid class with its indispensable role in photosynthesis and growth in land plants, algae, and cyanobacteria. PG is the only major phospholipid in the thylakoid membrane of cyanobacteria and plant chloroplasts and a main lipid component in photosynthetic protein-cofactor complexes such as photosystem I and photosystem II. In plants and algae, PG is also essential as a substrate for the biosynthesis of cardiolipin, which is a unique lipid present only in mitochondrial membranes and crucial for the functions of mitochondria. PG biosynthesis pathways in plants include three membranous organelles, plastids, mitochondria, and the endoplasmic reticulum in a complex manner. While the molecular biology underlying the role of PG in photosynthetic functions is well established, many enzymes responsible for the PG biosynthesis are only recently cloned and functionally characterized in the model plant species including Arabidopsis thaliana and Chlamydomonas reinhardtii and cyanobacteria such as Synechocystis sp. PCC 6803. The characterization of those enzymes helps understand not only the metabolic flow for PG production but also the crosstalk of biosynthesis pathways between PG and other lipids. This review aims to summarize recent advances in the understanding of the PG biosynthesis pathway and functions of involved enzymes.
  英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.plipres.2023.101266
  DOI ID：10.1016/j.plipres.2023.101266, PubMed ID：38040200
• Deacylation of galactolipids decomposes photosystem II dimers to enhance degradation of damaged D1 protein　　　　　　　　　　　　　　　
  Haruhiko Jimbo; Hajime Wada
  Plant Physiology, 2023年01月, ［査読有り］, ［筆頭著者, 責任著者］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/plphys/kiac460
  DOI ID：10.1093/plphys/kiac460, ORCID：157338607
• Crucial importance of length of fatty-acyl chains bound to the sn-2 position of phosphatidylglycerol for growth and photosynthesis of Synechocystis sp. PCC 6803　　　　　　　　　　　　　　　
  Kaichiro Endo; Masato Abe; Nobumasa Kawanishi; Haruhiko Jimbo; Koichi Kobayashi; Tomoko Suzuki; Noriko Nagata; Hideto Miyoshi; Hajime Wada
  Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 巻：1867, 号：7, 開始ページ：159158, 終了ページ：159158, 2022年07月, ［査読有り］
  Elsevier BV, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.bbalip.2022.159158
  DOI ID：10.1016/j.bbalip.2022.159158, ISSN：1388-1981
• Specific Incorporation of Polyunsaturated Fatty Acids into the sn-2 Position of Phosphatidylglycerol Accelerates Photodamage to Photosystem II under Strong Light
  Haruhiko Jimbo; Koki Yuasa; Kensuke Takagi; Takashi Hirashima; Sumie Keta; Makiko Aichi; Hajime Wada
  International Journal of Molecular Sciences, 2021年09月, ［査読有り］, ［筆頭著者, 責任著者］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.3390/ijms221910432
  DOI ID：10.3390/ijms221910432, ORCID：100648165
• Dissection of the Mechanisms of Growth Inhibition Resulting from Loss of the PII Protein in the Cyanobacterium Synechococcus elongatus PCC 7942　　　　　　　　　　　　　　　
  Takayuki Sakamoto; Nobuyuki Takatani; Kintake Sonoike; Haruhiko Jimbo; Yoshitaka Nishiyama; Tatsuo Omata
  Plant and Cell Physiology, 巻：62, 号：4, 開始ページ：721, 終了ページ：731, 2021年02月, ［査読有り］
  Abstract
  
  In cyanobacteria, the PII protein (the glnB gene product) regulates a number of proteins involved in nitrogen assimilation including PipX, the coactivator of the global nitrogen regulator protein NtcA. In Synechococcus elongatus PCC 7942, construction of a PII-less mutant retaining the wild-type pipX gene is difficult because of the toxicity of uncontrolled action of PipX and the other defect(s) resulting from the loss of PIIper se, but the nature of the PipX toxicity and the PipX-independent defect(s) remains unclear. Characterization of a PipX-less glnB mutant (PD4) in this study showed that the loss of PII increases the sensitivity of PSII to ammonium. Ammonium was shown to stimulate the formation of reactive oxygen species in the mutant cells. The ammonium-sensitive growth phenotype of PD4 was rescued by the addition of an antioxidant α-tocopherol, confirming that photo-oxidative damage was the major cause of the growth defect. A targeted PII mutant retaining wild-type pipX was successfully constructed from the wild-type S. elongatus strain (SPc) in the presence of α-tocopherol. The resulting mutant (PD1X) showed an unusual chlorophyll fluorescence profile, indicating extremely slow reduction and re-oxidation of QA, which was not observed in mutants defective in both glnB and pipX. These results showed that the aberrant action of uncontrolled PipX resulted in an impairment of the electron transport reactions in both the reducing and oxidizing sides of QA.
  Oxford University Press (OUP), 研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/pcp/pcab030
  DOI ID：10.1093/pcp/pcab030, ISSN：0032-0781, eISSN：1471-9053, ORCID：92396721, PubMed ID：33650637
• A START domain-containing protein is involved in the incorporation of ER-derived fatty acids into chloroplast glycolipids in Marchantia polymorpha　　　　　　　　　　　　　　　
  Takashi Hirashima; Haruhiko Jimbo; Koichi Kobayashi; Hajime Wada
  Biochemical and Biophysical Research Communications, 巻：534, 開始ページ：436, 終了ページ：441, 2020年11月, ［査読有り］, ［国際誌］
  The appropriate regulation of thylakoid lipid synthesis is essential for the function of chloroplasts. In plant cells, membrane lipids synthesized in the ER are utilized as a precursor for the synthesis of chloroplast glycolipids. This pathway is thought to be mediated by the transport of glycerolipids synthesized in the ER into chloroplasts. However, we have little knowledge about the proteins involved in the lipid transfer between these organelles in plant cells. Here we show a protein, STAR2, containing the START (Steroidogenic acute regulatory protein-related lipid transfer) domain known to function as a lipid transporter, is involved in the incorporation of ER-derived fatty acids into chloroplast glycolipids in Marchantia polymorpha. We found that STAR2 localizes on the chloroplast envelope membrane as a punctuate structure and is required for the increase of C20 fatty acids, which are synthesized in the ER, in chloroplast glycolipids in response to phosphate deprivation. Our results indicate that STAR2 of M. polymorpha is likely to be involved in the lipid transfer from ER to chloroplast, presumably as a lipid transporter.
  Elsevier {BV}, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.bbrc.2020.11.063
  DOI ID：10.1016/j.bbrc.2020.11.063, ISSN：0006-291X, ORCID：84066124, PubMed ID：33246557
• Membrane Lipid Remodeling is Required for Photosystem II Function under Low CO 2　　　　　　　　　　　　　　　
  Haruhiko Jimbo; Taichi Izuhara; Takashi Hirashima; Kaichiro Endo; Yuki Nakamura; Hajime Wada
  The Plant Journal, 巻：105, 号：1, 開始ページ：245, 終了ページ：253, 2020年10月, ［査読有り］, ［筆頭著者, 責任著者］
  Wiley, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1111/tpj.15054
  DOI ID：10.1111/tpj.15054, ISSN：0960-7412, eISSN：1365-313X, ORCID：82705184, PubMed ID：33119921
• Long-Chain Saturated Fatty Acids, Palmitic and Stearic Acids, Enhance the Repair of Photosystem II
  Haruhiko Jimbo; Kensuke Takagi; Takashi Hirashima; Yoshitaka Nishiyama; Hajime Wada
  International Journal of Molecular Sciences, 巻：21, 号：20, 開始ページ：7509, 終了ページ：7509, 2020年10月, ［査読有り］, ［筆頭著者, 責任著者］
  Free fatty acids (FFA) generated in cyanobacterial cells can be utilized for the biodiesel that is required for our sustainable future. The combination of FFA and strong light induces severe photoinhibition of photosystem II (PSII), which suppresses the production of FFA in cyanobacterial cells. In the present study, we examined the effects of exogenously added FFA on the photoinhibition of PSII in Synechocystis sp. PCC 6803. The addition of lauric acid (12:0) to cells accelerated the photoinhibition of PSII by inhibiting the repair of PSII and the de novo synthesis of D1. α-Linolenic acid (18:3) affected both the repair of and photodamage to PSII. Surprisingly, palmitic (16:0) and stearic acids (18:0) enhanced the repair of PSII by accelerating the de novo synthesis of D1 with the mitigation of the photoinhibition of PSII. Our results show chemical potential of FFA in the regulation of PSII without genetic manipulation.
  {MDPI} {AG}, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.3390/ijms21207509
  DOI ID：10.3390/ijms21207509, ISSN：1422-0067, eISSN：1422-0067, ORCID：82081227
• Elevated Levels of Specific Carotenoids During Acclimation to Strong Light Protect the Repair of Photosystem II in Synechocystis sp. PCC 6803
  Taichi Izuhara; Ikumi Kaihatsu; Haruhiko Jimbo; Shinichi Takaichi; Yoshitaka Nishiyama
  Frontiers in Plant Science, 巻：11, 2020年07月, ［査読有り］
  Frontiers Media SA, 研究論文（学術雑誌）
  DOI：https://doi.org/10.3389/fpls.2020.01030
  DOI ID：10.3389/fpls.2020.01030, ISSN：1664-462X, eISSN：1664-462X, ORCID：82081219
• Light-inducible expression of translation factor EF-Tu during acclimation to strong light enhances the repair of photosystem II.　　　　　　　　　　　　　　　
  Jimbo H; Izuhara T; Hihara Y; Hisabori T; Nishiyama Y
  Proceedings of the National Academy of Sciences of the United States of America, 巻：116, 号：42, 開始ページ：21268, 終了ページ：21273, 2019年09月, ［査読有り］, ［筆頭著者］
  In photosynthetic organisms, the repair of photosystem II (PSII) is enhanced after acclimation to strong light, with the resultant mitigation of photoinhibition of PSII. We previously reported that oxidation of translation elongation factor EF-Tu, which delivers aminoacyl-tRNA to the ribosome, depresses the repair of PSII in the cyanobacterium Synechocystis sp. PCC 6803. In the present study, we investigated the role of EF-Tu in the repair of PSII after acclimation of Synechocystis to strong light. In cells that had been grown under strong light, both the repair of PSII and the synthesis of proteins de novo were enhanced under strong light, with the resultant mitigation of photoinhibition of PSII. Moreover, levels of EF-Tu were elevated, whereas levels of other components of the translation machinery, such as translation factor EF-G and ribosomal proteins L2 and S12, did not change significantly. The expression of the gene for EF-Tu was induced by light, as monitored at the transcriptional level. Elevation of the level of EF-Tu was strongly correlated with the subsequent enhancement of PSII repair in cells that had been grown under light at various intensities. Furthermore, overexpression of EF-Tu in Synechocystis enhanced protein synthesis and PSII repair under strong light, even after cell culture under nonacclimating conditions. These observations suggest that elevation of the level of EF-Tu might be a critical factor in enhancing the capacity for repair of PSII that develops during acclimation to strong light.
  Proceedings of the National Academy of Sciences, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1073/pnas.1909520116
  DOI ID：10.1073/pnas.1909520116, ISSN：0027-8424, ORCID：82081216, PubMed ID：31570574
• Oxidation of translation factor EF-Tu inhibits the repair of photosystem II　　　　　　　　　　　　　　　
  Haruhiko Jimbo; Rayakorn Yutthanasirikul; Takanori Nagano; Toru Hisabori; Yukako Hihara; Yoshitaka Nishiyama
  Plant Physiology, 巻：176, 号：4, 開始ページ：2691, 終了ページ：2699, 2018年04月, ［査読有り］, ［筆頭著者］
  The repair of photosystem II (PSII) is particularly sensitive to oxidative stress and the inhibition of repair is associated with oxidative damage to the translational elongation system in the cyanobacterium Synechocystis sp. PCC 6803. However, the molecular mechanisms underlying this inhibition are unknown. We previously demonstrated in vitro that EF-Tu, a translation factor that delivers aminoacyl-tRNA to the ribosome, is inactivated by reactive oxygen species via oxidation of the Cys residue Cys-82. In this study, we examined the physiological role of the oxidation of EF-Tu in Synechocystis. Under strong light, EF-Tu was rapidly oxidized to yield oxidized monomers in vivo. We generated a Synechocystis transformant that expressed mutated EF-Tu in which Cys-82 had been replaced with a Ser residue. Under strong light, the de novo synthesis of proteins that are required for PSII repair, such as D1, was enhanced in the transformant and photoinhibition of PSII was alleviated. However, photodamage to PSII, measured in the presence of lincomycin, was similar between the transformant and wild-type cells, suggesting that expression of mutated EF-Tu might enhance the repair of PSII. Alleviating photoinhibition through mutation of EF-Tu did not alter cell growth under strong light, perhaps due to the enhanced production of reactive oxygen species. These observations suggest that the oxidation of EF-Tu under strong light inhibits PSII repair, resulting in the stimulation of photoinhibition.
  American Society of Plant Biologists, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1104/pp.18.00037
  DOI ID：10.1104/pp.18.00037, ISSN：1532-2548, ORCID：82081212, PubMed ID：29439212, SCOPUS ID：85045519528
• Oxidation of a Cysteine Residue in Elongation Factor EF-Tu Reversibly Inhibits Translation in the Cyanobacterium Synechocystis sp PCC 6803　　　　　　　　　　　　　　　
  Rayakorn Yutthanasirikul; Takanori Nagano; Haruhiko Jimbo; Yukako Hihara; Takashi Kanamori; Takuya Ueda; Takamitsu Haruyama; Hiroki Konno; Keisuke Yoshida; Toru Hisabori; Yoshitaka Nishiyama
  JOURNAL OF BIOLOGICAL CHEMISTRY, 巻：291, 号：11, 開始ページ：5860, 終了ページ：5870, 2016年03月, ［査読有り］
  Translational elongation is susceptible to inactivation by reactive oxygen species (ROS) in the cyanobacterium Synechocystis sp. PCC 6803, and elongation factor G has been identified as a target of oxidation by ROS. In the present study we examined the sensitivity to oxidation by ROS of another elongation factor, EF-Tu. The structure of EF-Tu changes dramatically depending on the bound nucleotide. Therefore, we investigated the sensitivity to oxidation in vitro of GTP- and GDP-bound EF-Tu as well as that of nucleotide-free EF-Tu. Assays of translational activity with a reconstituted translation system from Escherichia coli revealed that GTP-bound and nucleotide-free EF-Tu were sensitive to oxidation by H2O2, whereas GDP-bound EF-Tu was resistant to H2O2. The inactivation of EF-Tu was the result of oxidation of Cys-82, a single cysteine residue, and subsequent formation of both an intermolecular disulfide bond and sulfenic acid. Replacement of Cys-82 with serine rendered EF-Tu resistant to inactivation by H2O2, confirming that Cys-82 was a target of oxidation. Furthermore, oxidized EF-Tu was reduced and reactivated by thioredoxin. Gel-filtration chromatography revealed that some of the oxidized nucleotide-free EF-Tu formed large complexes of >30 molecules. Atomic force microscopy revealed that such large complexes dissociated into several smaller aggregates upon the addition of dithiothreitol. Immunological analysis of the redox state of EF-Tu in vivo showed that levels of oxidized EF-Tu increased under strong light. Thus, resembling elongation factor G, EF-Tu appears to be sensitive to ROS via oxidation of a cysteine residue, and its inactivation might be reversed in a redox-dependent manner.
  AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1074/jbc.M115.706424
  DOI ID：10.1074/jbc.M115.706424, ISSN：0021-9258, eISSN：1083-351X, ORCID：82081209, PubMed ID：26786107, Web of Science ID：WOS:000372551800032
• Zeaxanthin and Echinenone Protect the Repair of Photosystem II from Inhibition by Singlet Oxygen in Synechocystis sp PCC 6803　　　　　　　　　　　　　　　
  Yuri Kusama; Shuhei Inoue; Haruhiko Jimbo; Shinichi Takaichi; Kintake Sonoike; Yukako Hihara; Yoshitaka Nishiyama
  PLANT AND CELL PHYSIOLOGY, 巻：56, 号：5, 開始ページ：906, 終了ページ：916, 2015年05月, ［査読有り］
  Carotenoids are important components of antioxidative systems in photosynthetic organisms. We investigated the roles of zeaxanthin and echinenone in the protection of PSII from photoinhibition in Synechocystis sp. PCC 6803, using mutants of the cyanobacterium that lack these carotenoids. The activity of PSII in mutant cells deficient in either zeaxanthin or echinenone was more sensitive to strong light than the activity in wild-type cells, and the activity in mutant cells deficient in both carotenoids was hypersensitive to strong light, indicating that the absence of these carotenoids increased the extent of photoinhibition. Nonetheless, the rate of photodamage to PSII, as measured in the presence of chloramphenicol, which blocks the repair of PSII, was unaffected by the absence of either carotenoid, suggesting that these carotenoids might act by protecting the repair of PSII. Knockout of the gene for the so-called orange carotenoid protein (OCP), in which the 3'-hydroxyechinenone cofactor, a derivative of echinenone, is responsible for the thermal dissipation of excitation energy, increased the extent of photoinhibition but did not affect photodamage, suggesting that thermal dissipation also protects the repair of PSII. In mutant cells lacking OCP, as well as those lacking zeaxanthin and echinenone, the production of singlet oxygen was stimulated and the synthesis de novo of various proteins, including the D1 protein, was markedly suppressed under strong light. These observations suggest that the carotenoids and thermal dissipation might protect the repair of photodamaged PSII by depressing the levels of singlet oxygen that inhibits protein synthesis.
  OXFORD UNIV PRESS, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/pcp/pcv018
  DOI ID：10.1093/pcp/pcv018, ISSN：0032-0781, eISSN：1471-9053, PubMed ID：25663484, Web of Science ID：WOS:000355313900009
• Expression of a highly active catalase VktA in the cyanobacterium Synechococcus elongatus PCC 7942 alleviates the photoinhibition of photosystem II　　　　　　　　　　　　　　　
  Haruhiko Jimbo; Akiko Noda; Hidenori Hayashi; Takanori Nagano; Isao Yumoto; Yoshitake Orikasa; Hidetoshi Okuyama; Yoshitaka Nishiyama
  PHOTOSYNTHESIS RESEARCH, 巻：117, 号：1-3, 開始ページ：509, 終了ページ：515, 2013年11月, ［査読有り］, ［筆頭著者］
  The repair of photosystem II (PSII) after photodamage is particularly sensitive to reactive oxygen species-such as H2O2, which is abundantly produced during the photoinhibition of PSII. In the present study, we generated a transformant of the cyanobacterium Synechococcus elongatus PCC 7942 that expressed a highly active catalase, VktA, which is derived from a facultatively psychrophilic bacterium Vibrio rumoiensis, and examined the effect of expression of VktA on the photoinhibition of PSII. The activity of PSII in transformed cells declined much more slowly than in wild-type cells when cells were exposed to strong light in the presence of H2O2. However, the rate of photodamage to PSII, as monitored in the presence of chloramphenicol, was the same in the two lines of cells, suggesting that the repair of PSII was protected by the expression of VktA. The de novo synthesis of the D1 protein, which is required for the repair of PSII, was activated in transformed cells under the same stress conditions. Similar protection of the repair of PSII in transformed cells was also observed under strong light at a relatively low temperature. Thus, the expression of the highly active catalase mitigates photoinhibition of PSII by protecting protein synthesis against damage by H2O2 with subsequent enhancement of the repair of PSII.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s11120-013-9804-7
  DOI ID：10.1007/s11120-013-9804-7, ISSN：0166-8595, eISSN：1573-5079, PubMed ID：23456267, Web of Science ID：WOS:000326604900037

• PSII光阻害におけるD1の代謝回転へのPGの寄与　　　　　　　　　　　　　　　
  第32回植物脂質シンポジウム, 2019年, ［招待有り］
  2019年 - 2019年
• シアノバクテリアの強光ストレス応答における翻訳因子EF-Tuを介した光化学系IIの修復制御　　　　　　　　　　　　　　　
  神保晴彦
  ラン藻ゲノム交流会, 2018年, ［招待有り］
  2018年 - 2018年

• 日本植物生理学会
• 日本光合成学会
• 日本植物脂質研究会
• 日本植物学会

• 光合成の高速な修復機構の分子基盤の解明　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 若手研究, 2022年04月01日 - 2024年03月31日
  神保 晴彦, 東京大学
  配分額（総額）：4550000, 配分額（直接経費）：3500000, 配分額（間接経費）：1050000
  課題番号：22K14795
• 光化学系II複合体のアセンブリーと修復の動的な過程における脂質の機能　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 基盤研究(C), 基盤研究(C), 2020年04月01日 - 2023年03月31日
  和田 元; 神保 晴彦, 東京大学
  配分額（総額）：4290000, 配分額（直接経費）：3300000, 配分額（間接経費）：990000
  令和3年度に得られた成果は以下の通りである。
  1. 光阻害におけるPGの代謝回転の役割 強光によって損傷を受けたPSIIの修復にPGの分解が必要であることを明らかにするために、 PGの分解に関わっているホスホリパーゼ遺伝子を破壊した変異株を用いて、PSII活性の失活と修復について解析した。変異株では強光によって失活したPSIIの修復が大きく阻害されることから、PGの分解がPSIIの修復に必要であることが明らかとなった。また、D1の合成はPGの分解によって影響を受けないものの、D1の分解がPGの分解の抑制によって阻害されることから、D1をスムーズに分解するためにはPGの分解が必要であることが明らかになった。
  2. 光阻害におけるMGDGの代謝回転の役割 MGDGの分解に関わっているガラクトリパーゼ（Gla1）の遺伝子を破壊した変異株を用いて、光阻害におけるMGDGの代謝回転の役割を解析した。変異株ではPSIIの修復が阻害され、MGDGの分解もPSIIの修復に必要であることが明らかとなった。また、変異株ではPSIIの二量体が蓄積しており、野生株から精製したPSIIにGLa1を作用させると、二量体ではMGDGが分解されて単量体に解離することが観察された。さらに、Gla1の細胞内局在を調べたところ、Gla1はPSIIの二量体に結合していることが明らかになった。これらの結果から、Gla1は二量体においてMGDGを分解することでPSIIをモノマー化することが明らかになった。さらに、MGDGの分解は、PGの分解と同様にD1の分解に必要であることが明らかとなった。以上のことから、Gla1は二量体に作用してMGDGを分解することでPSIIをモノマー化し、D1の分解を促進するものと考えられる。
  課題番号：20K06701
• 光合成の修復における脂質代謝機構の解明　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 若手研究, 若手研究, 2019年04月01日 - 2021年03月31日
  神保 晴彦, 東京大学
  配分額（総額）：4290000, 配分額（直接経費）：3300000, 配分額（間接経費）：990000
  光合成は光エネルギーを使って、水から電子を引き抜き、細胞内へと供給している。その結果として、酸素と炭素固定産物が生み出され、地球上のほぼ全ての生物を支える礎となっている。しかし、過剰な光エネルギーは光合成を傷害し、不活性化してしまう。細胞内では、不活化した光合成を修復する機構があるが、膜脂質との関わりは不明であった。本研究では、膜脂質の代謝回転が光合成の修復過程に寄与していることを明らかにした。また、環境ストレスに応答した膜脂質の変化が光合成活性を維持する上で重要な働きを持つことを明らかにし、学術論文として発表した。
  課題番号：19K16161
• 光合成の強光順化の分子メカニズム解明　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, 2015年04月24日 - 2018年03月31日
  神保 晴彦, 埼玉大学
  配分額（総額）：2800000, 配分額（直接経費）：2800000
  本年度は、シアンバクテリアの強光応答における翻訳因子EF-Tuの役割について論文をPlant Physiologyに発表した。また、シアノバクテリアの強光順化におけるタンパク質合成活性への影響の解析を行った。昨年度までに、強光順化の過程でEF-Tu量が増大し、光化学系IIの修復が促進することを明らかにした。そこで、EF-Tu量と光化学系IIの強光耐性との関係を調べた。シアノバクテリアではEF-Tuの量が培養の光強度に応じて増大していた。さらに、翻訳因子EF-Gの量をウェスタンブロットで解析すると、EF-G量には変化がなかった。また、リボソームの大サブユニットに結合するL2タンパク質および小サブユニットに結合するS12タンパク質の量を解析すると、強光順化の過程で特に差は見られなかった。したがって、強光順化の過程ではEF-Tuが特異的に増大することが示唆された。また、強光に2時間晒した後の光化学系II比活性を解析し、光化学系IIの強光耐性の指標とした。その結果、光化学系IIの強光耐性と強光順化におけるEF-Tu量との間に高い正の相関があった。そこで、EF-Tuタンパク質を過剰に発現させた変異株を作製し、強光下における光化学系IIの強光耐性および強光下におけるタンパク質の新規合成活性を解析した。過剰発現株では強光1,500 μmol photonsの条件において、野生株に比べて光化学系IIの修復が促進していた。さらに過剰発現株では、野生株に比べてタンパク質の新規合成活性が促進していた。したがって、EF-Tuの過剰発現によって強光下におけるタンパク質合成が促進した結果、光化学系IIの修復が促進したと考えられる。すなわち、強光順化の過程では翻訳因子EF-Tu量の増大が重要な役割を担うことが明らかとなった。以上の研究内容を、国内学会および国際シンポジウムにて発表した。
  課題番号：15J10561