記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Academic Press Inc.  

DOI： 10.1016/bs.abr.2021.09.007

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担当区分：責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press (OUP)  

<title>Abstract</title>
Inorganic phosphate (Pi) and nitrogen (N) are essential nutrients for plant growth. We found that a five-fold oversupply of nitrate rescues Arabidopsis (Arabidopsis thaliana) plants from Pi-starvation stress. Analyses of transgenic plants that overexpressed GFP-AUTOPHAGY8 showed that an oversupply of nitrate induced autophagy flux under Pi-depleted conditions. Expression of DIN6 and DIN10, the carbon (C) starvation-responsive genes, was upregulated when nitrate was oversupplied under Pi starvation, which suggested that the plants recognized the oversupply of nitrate as C starvation stress because of the reduction in the C/N ratio. Indeed, formation of Rubisco-containing bodies (RCBs), which contain chloroplast stroma and are induced by C starvation, was enhanced when nitrate was oversupplied under Pi starvation. Moreover, autophagy-deficient mutants did not release Pi (unlike wild-type plants), exhibited no RCB accumulation inside vacuoles, and were hypersensitive to Pi starvation, indicating that RCB-mediated chlorophagy is involved in Pi starvation tolerance. Thus, our results showed that the Arabidopsis response to Pi starvation is closely linked with N and C availability and that autophagy is a key factor that controls plant growth under Pi starvation.

DOI： 10.1093/plphys/kiaa030

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press (OUP)  

<title>Abstract</title>
Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the major components of thylakoid membranes and well-conserved from cyanobacteria to chloroplasts. However, cyanobacteria and chloroplasts synthesize these galactolipids using different pathways and enzymes, but they are believed to share a common ancestor. This fact implies that there was a replacement of the cyanobacterial galactolipid biosynthesis pathway during the evolution of a chloroplast. In this study, we first replaced the cyanobacterial MGDG biosynthesis pathway in a model cyanobacterium, Synechococcus elongatus PCC 7942, with the corresponding plant-type pathway. No obvious phenotype was observed under the optimum growth condition, and the content of membrane lipids was not largely altered in the transformants. We next replaced the cyanobacterial DGDG biosynthesis pathway with the corresponding plant-type pathway using the strain described above and isolated the strain harboring the replaced plant-type pathway instead of the whole galactolipid biosynthesis pathway. This transformant, SeGPT, can grow photoautotrophically, indicating that cyanobacterial galactolipid biosynthesis pathways can be functionally complemented by the corresponding plant-type pathways and that the lipid products MGDG and DGDG, and not biosynthesis pathways, are important. While SeGPT does not show strong growth retardation, the strain has low cellular chlorophyll content but it retained a similar oxygen evolution rate per chlorophyll content compared with the wild type. An increase in total membrane lipid content was observed in SeGPT, which was caused by a significant increase in DGDG content. SeGPT accumulated carotenoids from the xanthophyll groups. These results suggest that cyanobacteria have the capacity to accept other pathways to synthesize essential components of thylakoid membranes.

DOI： 10.1093/pcp/pcaa090

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その他リンク： http://academic.oup.com/pcp/article-pdf/61/9/1661/33785187/pcaa090.pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

Membrane lipid remodeling under phosphate (Pi) limitation, a process that replaces structural membrane phospholipids with nonphosphorus lipids, is a widely observed adaptive response in plants and algae. Here, we identified the transcription factor phosphorus starvation response 1 (NoPSR1) as an indispensable player for regulating membrane lipid conversion during Pi starvation in the microalga Nannochloropsis oceanica. Knocking out NoPSR1 scarcely perturbed membrane lipid composition under Pi-sufficient conditions but significantly impaired dynamic alteration in membrane lipids during Pi starvation. In contrast, the absence of NoPSR1 led to no obvious change in cell proliferation or storage lipid accumulation under either nutrient-sufficient or Pi-deficient conditions. Our results demonstrate a key factor controlling the membrane lipid profile during the Pi starvation response in N. oceanica.

DOI： 10.1002/1873-3468.13902

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/1873-3468.13902

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

Thylakoid membranes, the site of photochemical and electron transport reactions of oxygenic photosynthesis, are composed of a myriad of proteins, cofactors including pigments, and glycerolipids. In the non-diazotrophic cyanobacterium Synechocystis sp. PCC 6803, the size and function of thylakoid membranes are reduced under nitrogen (N) starvation but are quickly recovered after N addition to the starved cells. To understand how the functionality of thylakoid membranes is adjusted in response to N status in Synechocystis sp. PCC 6803, we examined changes in thylakoid components and the photosynthetic activity during the N starvation and recovery processes. In N-starved cells, phycobilisome content, photosystem II protein levels and the photosynthetic activity substantially decreased as compared with those in N-sufficient cells. Although the content of chlorophyll (Chl) a, total protein and total glycerolipid also decreased under the N-starved condition based on OD730 reflecting cell density, when based on culture volume, the Chl a and total protein content remained almost constant and total glycerolipid content even increased during N starvation, suggesting that cellular levels of these components decrease under the N-starved condition mainly through dilution due to cell growth. With N addition, the photosynthetic activity quickly recovered, followed by full restoration of photosynthetic pigment and protein levels. The content of phosphatidylglycerol (PG), an essential lipid constituent of both photosystems, increased faster than that of Chl a, whereas the content of glycolipids, the main constituents of the thylakoid lipid bilayer, gradually recovered after N addition. The data indicate differential regulation of PG and glycolipids during the construction of the photosynthetic machinery and regeneration of thylakoid membranes. Of note, addition of PG to the growth medium slightly accelerated the Chl a accumulation in wild-type cells during the recovery process. Because PG is required for the biosynthesis of Chl a and the formation of functional photosystem complexes, rapid PG biosynthesis in response to N acquisition may be required for the rapid formation of the photosynthetic machinery during thylakoid regeneration.

DOI： 10.3389/fpls.2020.00432

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1111/tpj.14473

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/tpj.14473

掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1007/s11103-019-00891-1

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その他リンク： http://link.springer.com/article/10.1007/s11103-019-00891-1/fulltext.html

担当区分：責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

DOI： 10.3389/fpls.2019.00709

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

Aliphatic C-H bonds are one of the major organic signatures detected in Proterozoic organic microfossils, and their origin is a topic of interest. To investigate the influence of the presence of silica on the thermal alteration of aliphatic C-H bonds in prokaryotic cells during diagenesis, cyanobacteria Synechocystis sp. PCC6803 were heated at temperatures of 250-450°C. Changes in the infrared (IR) signals were monitored by micro-Fourier transform infrared (FTIR) spectroscopy. Micro-FTIR shows that absorbances at 2,925 cm-1 band (aliphatic CH2 ) and 2,960 cm-1 band (aliphatic CH3 ) decrease during heating, indicating loss of the C-H bonds, which was delayed by the presence of silica. A theoretical approach using solid-state kinetics indicates that the most probable process for the aliphatic C-H decrease is three-dimensional diffusion of alteration products under both non-embedded and silica-embedded conditions. The extrapolation of the experimental results obtained at 250-450°C to lower temperatures implies that the rate constant for CH3 (kCH3 ) is similar to or lower than that for CH2 (kCH2 ; i.e., CH3 decreases at a similar rate or more slowly than CH2 ). The peak height ratio of 2,960 cm-1 band (CH3 )/2,925 cm-1 band (CH2 ; R3/2 values) either increased or remained constant during the heating. These results reveal that the presence of silica does affect the decreasing rate of the aliphatic C-H bonds in cyanobacteria during thermal maturation, but that it does not significantly decrease the R3/2 values. Meanwhile, studies of microfossils suggest that the R3/2 values of Proterozoic prokaryotic fossils from the Bitter Springs Group and Gunflint Formation have decreased during fossilization, which is inconsistent with the prediction from our experimental results that R3/2 values did not decrease after silicification. Some process other than thermal degradation, possibly preservation of specific classes of biomolecules with low R3/2 values, might have occurred during fossilization.

DOI： 10.1111/gbi.12294

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1111/nph.15070

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Plant Biologists (ASPB)  

Diacylglyceryl-N,N,N-trimethylhomo-Ser (DGTS) is a nonphosphorous, polar glycerolipid that is regarded as analogous to the phosphatidylcholine in bacteria, fungi, algae, and basal land plants. In some species of algae, including the stramenopile microalga Nannochloropsis oceanica, DGTS contains an abundance of eicosapentaenoic acid (EPA), which is relatively scarce in phosphatidylcholine, implying that DGTS has a unique physiological role. In this study, we addressed the role of DGTS in N. oceanica We identified two DGTS biosynthetic enzymes that have distinct domain configurations compared to previously identified DGTS synthases. Mutants lacking DGTS showed growth retardation under phosphate starvation, demonstrating a pivotal role for DGTS in the adaptation to this condition. Under normal conditions, DGTS deficiency led to an increase in the relative amount of monogalactosyldiacylglycerol, a major plastid membrane lipid with high EPA content, whereas excessive production of DGTS induced by gene overexpression led to a decrease in monogalactosyldiacylglycerol. Meanwhile, lipid analysis of partial phospholipid-deficient mutants revealed a role for phosphatidylcholine and phosphatidylethanolamine in EPA biosynthesis. These results suggest that DGTS and monogalactosyldiacylglycerol may constitute the two major pools of EPA in extraplastidic and plastidic membranes, partially competing to acquire EPA or its precursors derived from phospholipids. The mutant lacking DGTS also displayed impaired growth and a lower proportion of EPA in extraplastidic compartments at low temperatures. Our results indicate that DGTS is involved in the adaptation to low temperatures through a mechanism that is distinct from the DGTS-dependent adaptation to phosphate starvation in N. oceanica.

DOI： 10.1104/pp.17.01573

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1038/s41477-017-0082-9

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その他リンク： http://www.nature.com/articles/s41477-017-0082-9.pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

DOI： 10.3389/fpls.2017.01847

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.bbalip.2016.04.015

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PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

Klebsormidium flaccidum is a charophytic alga living in terrestrial and semiaquatic environments. K. flaccidum grows in various habitats, such as low-temperature areas and under desiccated conditions, because of its ability to tolerate harsh environments. Wax and cuticle polymers that contribute to the cuticle layer of plants are important for the survival of land plants, as they protect against those harsh environmental conditions and were probably critical for the transition from aquatic microorganism to land plants. Bryophytes, non-vascular land plants, have similar, but simpler, extracellular waxes and polyester backbones than those of vascular plants. The presence of waxes in terrestrial algae, especially in charophytes, which are the closest algae to land plants, could provide clues in elucidating the mechanism of land colonization by plants. Here, we compared genes involved in the lipid biosynthetic pathways of Arabidopsis thaliana to the K. flaccidum and the Chlamydomonas reinhardtii genomes, and identified wax-related genes in both algae. A simple and easy extraction method was developed for the recovery of the surface lipids from K. flaccidum and C. reinhardtii. Although these algae have wax components, their surface lipids were largely different from those of land plants. We also investigated aliphatic substances in the cell wall fraction of K. flaccidum and C. reinhardtii. Many of the fatty acids were determined to be lipophilic monomers in K. flaccidum, and a Fourier transform infrared spectroscopic analysis revealed that their possible binding mode was distinct from that of A. thaliana. Thus, we propose that K. flaccidum has a cuticle-like hydrophobic layer composed of lipids and glycoproteins, with a different composition from the cutin polymer typically found in land plant cuticles.

DOI： 10.3389/fpls.2016.00952

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Informa UK Limited  

Most microalgae abundantly accumulate lipid droplets (LDs) containing triacylglycerols (TAGs) under several stress conditions, but the underlying molecular mechanism of this accumulation remains unclear. In a recent study, we found that inhibition of TOR (target of rapamycin), a highly conserved protein kinase of eukaryotes, by rapamycin resulted in TAG accumulation in microalgae, indicating that TOR negatively regulates TAG accumulation. Here, we show that formation of intracellular LDs and TAG accumulation were also induced in the unicellular green alga Chlamydomonas reinhardtii after exposure to Torin1 or AZD8055, which are novel TOR inhibitors that inhibit TOR activity in a manner different from rapamycin. These results supported quite well our previous conclusion that TOR is a central regulator of TAG accumulation in microalgae.

DOI： 10.1080/15592324.2016.1149285

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

Most microalgae produce triacylglycerol (TAG) under stress conditions such as nitrogen depletion, but the underlying molecular mechanism remains unclear. In this study, we focused on the role of target of rapamycin (TOR) in TAG accumulation. TOR is a serine/threonine protein kinase that is highly conserved and plays pivotal roles in nitrogen and other signaling pathways in eukaryotes. We previously constructed a rapamycin-susceptible Cyanidioschyzon merolae, a unicellular red alga, by expressing yeast FKBP12 protein to evaluate the results of TOR inhibition (Imamura et al. in Biochem Biophys Res Commun 439:264-269, 2013). By using this strain, we here report that rapamycin-induced TOR inhibition results in accumulation of cytoplasmic lipid droplets containing TAG. Transcripts for TAG synthesis-related genes, such as glycerol-3-phosphate acyltransferase and acyl-CoA:diacylglycerol acyltransferase (DGAT), were increased by rapamycin treatment. We also found that fatty acid synthase-dependent de novo fatty acid synthesis was required for the accumulation of lipid droplets. Induction of TAG and up-regulation of DGAT gene expression by rapamycin were similarly observed in the unicellular green alga, Chlamydomonas reinhardtii. These results suggest the general involvement of TOR signaling in TAG accumulation in divergent microalgae.

DOI： 10.1007/s11103-015-0370-6

PubMed

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その他リンク： http://link.springer.com/article/10.1007/s11103-015-0370-6/fulltext.html

掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

DOI： 10.3389/fmicb.2015.00912

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers Media SA  

DOI： 10.3389/fpls.2015.00664

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1111/pbi.12210

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/pbi.12210

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3389/fpls.2014.00280

Web of Science

PubMed

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記述言語：英語  

The colonization of land by plants was a key event in the evolution of life. Here we report the draft genome sequence of the filamentous terrestrial alga Klebsormidium flaccidum (Division Charophyta, Order Klebsormidiales) to elucidate the early transition step from aquatic algae to land plants. Comparison of the genome sequence with that of other algae and land plants demonstrate that K. flaccidum acquired many genes specific to land plants. We demonstrate that K. flaccidum indeed produces several plant hormones and homologues of some of the signalling intermediates required for hormone actions in higher plants. The K. flaccidum genome also encodes a primitive system to protect against the harmful effects of high-intensity light. The presence of these plant-related systems in K. flaccidum suggests that, during evolution, this alga acquired the fundamental machinery required for adaptation to terrestrial environments.

DOI： 10.1038/ncomms4978

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.bbalip.2013.12.007

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Scopus

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その他リンク： http://orcid.org/0000-0002-5349-4927

DOI： 10.3389/fpls.2013.00469

Scopus

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その他リンク： http://orcid.org/0000-0002-5349-4927

掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press (OUP)  

DOI： 10.1093/dnares/dsr044

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1758-2229.2011.00277.x

Web of Science

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Plant Biologists (ASPB)  

DOI： 10.1105/tpc.111.085357

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.plipres.2011.02.003

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.plipres.2011.03.001

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1016/j.febslet.2011.04.010

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出版者・発行元：日本植物生理学会  

植物の葉緑体膜はMonogalactosyldiacylglycerol (MGDG)やDigalactosyldiacylglycerol (DGDG)といったグリセロ糖脂質によって占められている一方、その他の膜は動物等と同様主にリン脂質によって構成されている。しかしリン酸欠乏条件下では、植物はこれらのリン脂質を分解し、代替脂質としてDGDGを葉緑体外に蓄積することが知られている。糖脂質合成酵素であるMGDG synthase 2 (MGD2)は、リン酸欠乏時特異的にDGDGの前駆体となるMGDG合成を行う酵素であり、この酵素のmRNAレベルはリン酸欠乏時に大きく上昇することがシロイヌナズナにおいて明らかとなっている。本研究では、リン欠乏時における発現制御機構を明らかにするため、シロイヌナズナMGD2遺伝子のプロモーター解析を行った。すなわち、MGD2上流に存在するプロモーター領域を段階的に短くし、その短くなったプロモーター配列の制御下で、レポーター遺伝子であるβ-glucuronidase (GUS)を発現させるベクターを作成し、シロイヌナズナに導入した。これらの形質転換された植物を用いてレポーター遺伝子の発現を調べた結果、プロモーター上流に通常時のMGD2の発現抑制を行う配列とリン酸欠乏応答に関わる領域を見出したので報告する。

DOI： 10.14841/jspp.2011.0.0919.0

CiNii Research

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society for Microbiology  

<title>ABSTRACT</title>
The Na⁺-dependent K⁺ uptake KtrABE system is essential for the adaptation of <italic>Synechocystis</italic> to salinity stress and high osmolality. While KtrB forms the K⁺-translocating pore, the role of the subunits KtrA and KtrE for Ktr function remains elusive. Here, we characterized the role of KtrA and KtrE in Ktr-mediated K⁺ uptake and in modulating Na⁺ dependency. Expression of KtrB alone in a K⁺ uptake-deficient <italic>Escherichia coli</italic> strain conferred low K⁺ uptake activity that was not stimulated by Na⁺. Coexpression of both KtrA and KtrE with KtrB increased the K⁺ transport activity in a Na⁺-dependent manner. KtrA and KtrE were found to be localized to the plasma membrane in <italic>Synechocystis</italic>. Site-directed mutagenesis was used to analyze the role of single charged residues in KtrB for Ktr function. Replacing negatively charged residues facing the extracellular space with residues of the opposite charge increased the apparent <italic>K_m
</italic> for K⁺ in all cases. However, none of the mutations eliminated the Na⁺ dependency of Ktr-mediated K⁺ transport. Mutations of residues on the cytoplasmic side had larger effects on K⁺ uptake activity than those of residues on the extracellular side. Further analysis revealed that replacement of R262, which is well conserved among Ktr/Trk/HKT transporters in the third extracellular loop, by Glu abolished transport activity. The atomic-scale homology model indicated that R262 might interact with E247 and D261. Based on these data, interaction of KtrA and KtrE with KtrB increased the K⁺ uptake rate and conferred Na⁺ dependency.

DOI： 10.1128/jb.00569-10

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s11103-010-9639-y

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その他リンク： http://orcid.org/0000-0003-3726-4790

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1073/pnas.0907173106

Web of Science

PubMed

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記述言語：日本語   出版者・発行元：バイオインダストリー協会  

CiNii Books

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.precamres.2009.03.006

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1016/j.febslet.2009.06.033

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Plant Biologists (ASPB)  

DOI： 10.1105/tpc.108.063925

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.abb.2005.02.005

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press (OUP)  

DOI： 10.1093/pcp/pcg110

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/s0003-9861(03)00112-7

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1006/bbrc.2001.5358

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1046/j.1432-1327.1999.00801.x

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Proceedings of the National Academy of Sciences  

DOI： 10.1073/pnas.94.1.333

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Web of Science

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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記述言語：日本語  

J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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記述言語：日本語  

J-GLOBAL

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記述言語：日本語  

J-GLOBAL

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）  

Web of Science

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記述言語：日本語  

DOI： 10.14841/jspp.2009.0.0796.0

J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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記述言語：日本語   出版者・発行元：Japan Society for Bioscience, Biotechnology, and Agrochemistry  

高等植物の葉緑体チラコイド膜を構成する脂質は，他の生物の生体膜とは大きく異なる特徴をもっている．通常，生体膜はリン脂質により構成されているが，チラコイド膜においてはガラクトースを含む2種類の糖脂質が主要構成脂質で，さらに微量ではあるが光合成生物に特徴的な硫黄糖スルホキノボースを含むスルホ脂質が含まれている．植物葉緑体に特徴的なこれら3つの糖脂質の生合成機構に関する研究の変遷と，最近得られた新しい知見を含めて，一連の研究で明らかになってきたこれらの糖脂質の重要な役割について紹介する．

DOI： 10.1271/kagakutoseibutsu.46.330

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00313869400?from=CiNii

記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）  

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記述言語：英語  

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記述言語：日本語   出版者・発行元：共立出版  

CiNii Books

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記述言語：英語  

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記述言語：英語  

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記述言語：英語  

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記述言語：英語   出版者・発行元：Japanese Society of Plant Physiologists  

Changes in the activity of UDP-galactose:diacylglycerol galactosyltransferase (UDGT), a key enzyme in galactolipid biosynthesis, during germination were investigated in cucumber (Cucumis sativus L. cv. Aonagajibai) seedlings. After germination, UDGT activity increased during growth in darkness for 4 days, reaching 10 times the activity in ungerminated seeds. Illumination of 4-day-old dark-grown seedlings strongly stimulated the activity. By contrast, in seedlings grown continuously in darkness, the increase in UDGT activity ceased after 4 days and the activity remained constant thereafter. A similar increase in the specific activity of UDGT was observed in the envelope fraction from seedlings, indicating that the increase in the enzymatic activity preceded synthesis of other proteins in the envelope membrane. Coincident with the change in the enzymatic activity, here was an increase in levels of monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG), two major constituents of chloroplast membrane lipids, in the germinated seedlings. Cycloheximide inhibited the light-mediated increase in the enzymatic activity by illumination of 4-day-old dark-grown seedlings, and, as a consequence, it inhibited the accumulation of MGDG and DGDG. It was clear, therefore, that protein synthesis was necessary during this activation. Addition of a cytokinin, benzyladenine (BA), stimulated the increase in the UDGT activity. The increase in the UDGT activity caused by BA was accompanied by the accumulation of galactolipids, as in the case of the activation by light. These results suggest that activation of the final reaction in the synthesis of MGDG, which is catalyzed by the galactosyltransferase, contributes to the accumulation of galactolipids during the development of the chloroplast membrane.

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その他リンク： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=182411

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2024年9月

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開催年月日： 2024年9月

記述言語：日本語   会議種別：ポスター発表  

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開催年月日： 2024年9月

記述言語：日本語   会議種別：ポスター発表  

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開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

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