Advance

SAKO Kaori

    Department of Advanced Bioscience　Lecturer
Last Updated :2024/04/19

Researcher Information

J-Global ID

Research Areas

  • Life sciences / Plants: molecular biology and physiology

Published Papers

  • Khurram Bashir; Daisuke Todaka; Sultana Rasheed; Akihiro Matsui; Zarnab Ahmad; Kaori Sako; Yoshinori Utsumi; Anh Thu Vu; Maho Tanaka; Satoshi Takahashi; Junko Ishida; Yuuri Tsuboi; Shunsuke Watanabe; Yuri Kanno; Eigo Ando; Kwang-Chul Shin; Makoto Seito; Hinata Motegi; Muneo Sato; Rui Li; Saya Kikuchi; Miki Fujita; Miyako Kusano; Makoto Kobayashi; Yoshiki Habu; Atsushi J Nagano; Kanako Kawaura; Jun Kikuchi; Kazuki Saito; Masami Yokota Hirai; Mitsunori Seo; Kazuo Shinozaki; Toshinori Kinoshita; Motoaki Seki
    Plant and Cell Physiology Oxford University Press (OUP) 63 (9) 1181 - 1192 0032-0781 2022/08 
    Abstract Water scarcity is a serious agricultural problem causing significant losses to crop yield and product quality. The development of technologies to mitigate the damage caused by drought stress is essential for ensuring a sustainable food supply for the increasing global population. We herein report that the exogenous application of ethanol, an inexpensive and environmentally friendly chemical, significantly enhances drought tolerance in Arabidopsis thaliana, rice and wheat. The transcriptomic analyses of ethanol-treated plants revealed the upregulation of genes related to sucrose and starch metabolism, phenylpropanoids and glucosinolate biosynthesis, while metabolomic analysis showed an increased accumulation of sugars, glucosinolates and drought-tolerance-related amino acids. The phenotyping analysis indicated that drought-induced water loss was delayed in the ethanol-treated plants. Furthermore, ethanol treatment induced stomatal closure, resulting in decreased transpiration rate and increased leaf water contents under drought stress conditions. The ethanol treatment did not enhance drought tolerance in the mutant of ABI1, a negative regulator of abscisic acid (ABA) signaling in Arabidopsis, indicating that ABA signaling contributes to ethanol-mediated drought tolerance. The nuclear magnetic resonance analysis using 13C-labeled ethanol indicated that gluconeogenesis is involved in the accumulation of sugars. The ethanol treatment did not enhance the drought tolerance in the aldehyde dehydrogenase (aldh) triple mutant (aldh2b4/aldh2b7/aldh2c4). These results show that ABA signaling and acetic acid biosynthesis are involved in ethanol-mediated drought tolerance and that chemical priming through ethanol application regulates sugar accumulation and gluconeogenesis, leading to enhanced drought tolerance and sustained plant growth. These findings highlight a new survival strategy for increasing crop production under water-limited conditions.
  • Anh Thu Vu; Yoshinori Utsumi; Chikako Utsumi; Maho Tanaka; Satoshi Takahashi; Daisuke Todaka; Yuri Kanno; Mitsunori Seo; Eigo Ando; Kaori Sako; Khurram Bashir; Toshinori Kinoshita; Xuan Hoi Pham; Motoaki Seki
    Plant Molecular Biology Springer Science and Business Media LLC 0167-4412 2022/08 
    External application of ethanol enhances tolerance to high salinity, drought, and heat stress in various plant species. However, the effects of ethanol application on increased drought tolerance in woody plants, such as the tropical crop "cassava," remain unknown. In the present study, we analyzed the morphological, physiological, and molecular responses of cassava plants subjected to ethanol pretreatment and subsequent drought stress treatment. Ethanol pretreatment induced a slight accumulation of abscisic acid (ABA) and stomatal closure, resulting in a reduced transpiration rate, higher water content in the leaves during drought stress treatment and the starch accumulation in leaves. Transcriptomic analysis revealed that ethanol pretreatment upregulated the expression of ABA signaling-related genes, such as PP2Cs and AITRs, and stress response and protein-folding-related genes, such as heat shock proteins (HSPs). In addition, the upregulation of drought-inducible genes during drought treatment was delayed in ethanol-pretreated plants compared with that in water-pretreated control plants. These results suggest that ethanol pretreatment induces stomatal closure through activation of the ABA signaling pathway, protein folding-related response by activating the HSP/chaperone network and the changes in sugar and starch metabolism, resulting in increased drought avoidance in plants.
  • Haruki Onosato; Genya Fujimoto; Tomota Higami; Takuya Sakamoto; Ayaka Yamada; Takamasa Suzuki; Rika Ozawa; Sachihiro Matsunaga; Motoaki Seki; Minoru Ueda; Kaori Sako; Ivan Galis; Gen-Ichiro Arimura
    Plant physiology 189 (2) 922 - 933 2022/06 
    Plants perceive volatiles emitted from herbivore-damaged neighboring plants to urgently adapt or prime their defense responses to prepare for forthcoming herbivores. Mechanistically, these volatiles can induce epigenetic regulation based on histone modifications that alter the transcriptional status of defense genes, but little is known about the underlying mechanisms. To understand the roles of such epigenetic regulation of plant volatile signaling, we explored the response of Arabidopsis (Arabidopsis thaliana) plants to the volatile β-ocimene. Defense traits of Arabidopsis plants toward larvae of Spodoptera litura were induced in response to β-ocimene, through enriched histone acetylation and elevated transcriptional levels of defense gene regulators, including ethylene response factor genes (ERF8 and ERF104) in leaves. The enhanced defense ability of the plants was maintained for 5 d but not over 10 d after exposure to β-ocimene, and this coincided with elevated expression of those ERFs in their leaves. An array of histone acetyltransferases, including HAC1, HAC5, and HAM1, were responsible for the induction and maintenance of the anti-herbivore property. HDA6, a histone deacetylase, played a role in the reverse histone remodeling. Collectively, our findings illuminate the role of epigenetic regulation in plant volatile signaling.
  • Kaori Sako; Ryutaro Nagashima; Masahiro Tamoi; Motoaki Seki
    Plant biotechnology (Tokyo, Japan) 38 (3) 339 - 344 2021/09 
    Abiotic stresses, such as high light and salinity, are major factors that limit crop productivity and sustainability worldwide. Chemical priming is a promising strategy for improving the abiotic stress tolerance of plants. Recently, we discovered that ethanol enhances high-salinity stress tolerance in Arabidopsis thaliana and rice by detoxifying reactive oxygen species (ROS). However, the effect of ethanol on other abiotic stress responses is unclear. Therefore, we investigated the effect of ethanol on the high-light stress response. Measurement of chlorophyll fluorescence showed that ethanol mitigates photoinhibition under high-light stress. Staining with 3,3'-diaminobenzidine (DAB) showed that the accumulation of hydrogen peroxide (H2O2) was inhibited by ethanol under high-light stress conditions in A. thaliana. We found that ethanol increased the gene expressions and enzymatic activities of antioxidative enzymes, including ASCORBATE PEROXIDASE1 (AtAPX1), Catalase (AtCAT1 and AtCAT2). Moreover, the expression of flavonoid biosynthetic genes and anthocyanin contents were upregulated by ethanol treatment during exposure to high-light stress. These results imply that ethanol alleviates oxidative damage from high-light stress in A. thaliana by suppressing ROS accumulation. Our findings support the hypothesis that ethanol improves tolerance to multiple stresses in field-grown crops.
  • Kaori Sako; Chien Van Ha; Akihiro Matsui; Maho Tanaka; Ayato Sato; Motoaki Seki
    Plants (Basel, Switzerland) 10 (5) 2021/05 
    Salinity stress is a major threat to agriculture and global food security. Chemical priming is a promising approach to improving salinity stress tolerance in plants. To identify small molecules with the capacity to enhance salinity stress tolerance in plants, chemical screening was performed using Arabidopsis thaliana. We screened 6400 compounds from the Nagoya University Institute of Transformative Bio-Molecule (ITbM) chemical library and identified one compound, Natolen128, that enhanced salinity-stress tolerance. Furthermore, we isolated a negative compound of Natolen128, namely Necolen124, that did not enhance salinity stress tolerance, though it has a similar chemical structure to Natolen128. We conducted a transcriptomic analysis of Natolen128 and Necolen124 to investigate how Natolen128 enhances high-salinity stress tolerance. Our data indicated that the expression levels of 330 genes were upregulated by Natolen128 treatment compared with that of Necolen124. Treatment with Natolen128 increased expression of hypoxia-responsive genes including ethylene biosynthetic enzymes and PHYTOGLOBIN, which modulate accumulation of nitric oxide (NO) level. NO was slightly increased in plants treated with Natolen128. These results suggest that Natolen128 may regulate NO accumulation and thus, improve salinity stress tolerance in A. thaliana.
  • Kaori Sako; Huong Mai Nguyen; Motoaki Seki
    Plant & cell physiology 2020/09 [Refereed]
     
    Abiotic stress is considered as a major factor limiting crop yield and quality. Development of effective strategies that mitigate abiotic stress is essential for sustainable agriculture and food security, especially with continuing global population growth. Recent studies have demonstrated that exogenous treatment of plants with chemical compounds can enhance abiotic stress tolerance by inducing molecular and physiological defense mechanisms, a process known as chemical priming. Chemical priming is believed to represent a promising strategy for mitigating abiotic stress in crop plants. Plants biosynthesize various compounds, such as phytohormones and other metabolites, to adapt to adverse environments. Research on artificially synthesized compounds has also resulted in the identification of novel compounds that improve abiotic stress tolerance. In this review, we summarize our current knowledge of both naturally synthesized and artificial priming agents that have been shown to increase abiotic stress tolerance in plants.
  • Kaori Sako; Yushi Futamura; Takeshi Shimizu; Akihiro Matsui; Hiroyuki Hirano; Yasumitsu Kondoh; Makoto Muroi; Harumi Aono; Maho Tanaka; Kaori Honda; Kenshirou Shimizu; Makoto Kawatani; Takeshi Nakano; Hiroyuki Osada; Ko Noguchi; Motoaki Seki
    Scientific reports 10 (1) 8691 - 8691 2020/05 [Refereed]
     
    Chemical priming is an attractive and promising approach to improve abiotic stress tolerance in a broad variety of plant species. We screened the RIKEN Natural Products Depository (NPDepo) chemical library and identified a novel compound, FSL0260, enhancing salinity-stress tolerance in Arabidopsis thaliana and rice. Through transcriptome analysis using A. thaliana seedlings, treatment of FSL0260 elevated an alternative respiration pathway in mitochondria that modulates accumulation of reactive oxygen species (ROS). From comparison analysis, we realized that the alternative respiration pathway was induced by treatment of known mitochondrial inhibitors. We confirmed that known inhibitors of mitochondrial complex I, such as rotenone and piericidin A, also enhanced salt-stress tolerance in Arabidopsis. We demonstrated that FSL0260 binds to complex I of the mitochondrial electron transport chain and inhibits its activity, suggesting that inhibition of mitochondrial complex I activates an alternative respiration pathway resulting in reduction of ROS accumulation and enhancement of tolerance to salinity in plants. Furthermore, FSL0260 preferentially inhibited plant mitochondrial complex I rather than a mammalian complex, implying that FSL0260 has a potential to be an agent for improving salt-stress tolerance in agriculture that is low toxicity to humans.
  • Bart Rymen; Ayako Kawamura; Alice Lambolez; Soichi Inagaki; Arika Takebayashi; Akira Iwase; Yuki Sakamoto; Kaori Sako; David S Favero; Momoko Ikeuchi; Takamasa Suzuki; Motoaki Seki; Tetsuji Kakutani; François Roudier; Keiko Sugimoto
    Communications biology 2 404 - 404 2019 [Refereed]
     
    Plant somatic cells reprogram and regenerate new tissues or organs when they are severely damaged. These physiological processes are associated with dynamic transcriptional responses but how chromatin-based regulation contributes to wound-induced gene expression changes and subsequent cellular reprogramming remains unknown. In this study we investigate the temporal dynamics of the histone modifications H3K9/14ac, H3K27ac, H3K4me3, H3K27me3, and H3K36me3, and analyze their correlation with gene expression at early time points after wounding. We show that a majority of the few thousand genes rapidly induced by wounding are marked with H3K9/14ac and H3K27ac before and/or shortly after wounding, and these include key wound-inducible reprogramming genes such as WIND1, ERF113/RAP2.6 L and LBD16. Our data further demonstrate that inhibition of GNAT-MYST-mediated histone acetylation strongly blocks wound-induced transcriptional activation as well as callus formation at wound sites. This study thus uncovered a key epigenetic mechanism that underlies wound-induced cellular reprogramming in plants.
  • Epigenetic regulations and modifications for enhanced salinity stress tolerance in plants
    Ueda, M; Sako, K; Seki, M
    Salinity Responses and Tolerance in Plants, Volume 2: Exploring RNAi, Genome Editing and Systems Biology 2018/12 [Refereed]
  • Huong Mai Nguyen; Kaori Sako; Akihiro Matsui; Minoru Ueda; Maho Tanaka; Akihiro Ito; Norikazu Nishino; Minoru Yoshida; Motoaki Seki
    Plant signaling & behavior 13 (3) e1448333  1559-2316 2018/03 [Refereed]
     
    Histone acetylation plays a pivotal role in plant growth and development, and is regulated by the antagonistic relationship between histone acetyltransferase (HAT) and histone deacetylase (HDAC). We previously revealed that some HDAC inhibitors confer high-salinity stress tolerance in plants. In this study, we identified two HDAC inhibitors, namely Ky-9 and Ky-72, which enhanced the high-salinity stress tolerance of Arabidopsis thaliana. Ky-9 and Ky-72 are structurally similar chlamydocin analogs. However, the in vitro inhibitory activity of Ky-9 against mammalian HDAC is greater than that of Ky-72. A western blot indicated that Ky-9 and Ky-72 increased the acetylation levels of histone H3, suggesting they exhibit HDAC inhibitory activities in plants. We conducted a transcriptomic analysis to investigate how Ky-9 and Ky-72 enhance high-salinity stress tolerance. Although Ky-9 upregulated the expression of more genes than Ky-72, similar gene expression patterns were induced by both HDAC inhibitors. Additionally, the expression of high-salinity stress tolerance-related genes, such as anthocyanin-related genes and a small peptide-encoding gene, increased by Ky-9 and Ky-72. These data suggest that slight structural differences in chemical side chain between HDAC inhibitors can alter inhibitory effect on HDAC protein leading to influence gene expression, thereby enhancing high-salinity stress tolerance in different extent.
  • Kaori Sako; Yuji Sunaoshi; Maho Tanaka; Akihiro Matsui; Motoaki Seki
    Plant signaling & behavior 13 (8) e1500065  1559-2316 2018 [Refereed]
     
    High-salinity stress affects plant growth and crop yield, so the development of techniques to enhance plant tolerance to such stress is important. Recently, we revealed that ethanol enhances high-salinity stress tolerance in Arabidopsis thaliana and rice by detoxifying Reactive Oxygen Species (ROS). However, we did not investigate how long salt stress tolerance was maintained following treatment with ethanol. Therefore, we herein analyzed survival rates and expression levels of AtZAT12, which is a transcriptional factor of ROS detoxification enzymes, under different conditions in Arabidopsis. Our results showed that ethanol-mediated high-salinity stress tolerance was lost after a 24 h break in ethanol treatment in ~ 1-week-old plants. Although ethanol enhanced salt stress tolerance, high concentrations of ethanol negatively affected plant growth. Thus, these data support the idea that adjustments of the frequency and amount of ethanol application to plants is useful to enhance salt stress tolerance without growth inhibition in the agricultural field.
  • Minoru Ueda; Akihiro Matsui; Maho Tanaka; Tomoe Nakamura; Takahiro Abe; Kaori Sako; Taku Sasaki; Jong-Myong Kim; Akihiro Ito; Norikazu Nishino; Hiroaki Shimada; Minoru Yoshida; Motoaki Seki
    PLANT PHYSIOLOGY AMER SOC PLANT BIOLOGISTS 175 (4) 1760 - 1773 0032-0889 2017/12 [Refereed]
     
    Histone acetylation is an essential process in the epigenetic regulation of diverse biological processes, including environmental stress responses in plants. Previously, our research group identified a histone deacetylase (HDAC) inhibitor (HDI) that confers salt tolerance in Arabidopsis (Arabidopsis thaliana). In this study, we demonstrate that class I HDAC (HDA19) and class II HDACs (HDA5/14/15/18) control responses to salt stress through different pathways. The screening of 12 different selective HDIs indicated that seven newly reported HDIs enhance salt tolerance. Genetic analysis, based on a pharmacological study, identified which HDACs function in salinity stress tolerance. In the wild-type Columbia-0 background, hda19 plants exhibit tolerance to high-salinity stress, while hda5/14/15/18 plants exhibit hypersensitivity to salt stress. Transcriptome analysis revealed that the effect of HDA19 deficiency on the response to salinity stress is distinct from that of HDA5/14/15/18 deficiencies. In hda19 plants, the expression levels of stress tolerance-related genes, late embryogenesis abundant proteins that prevent protein aggregation and positive regulators such as ABI5 and NAC019 in abscisic acid signaling, were induced strongly relative to the wild type. Neither of these elements was up-regulated in the hda5/14/15/18 plants. The mutagenesis of HDA19 by genome editing in the hda5/14/15/18 plants enhanced salt tolerance, suggesting that suppression of HDA19 masks the phenotype caused by the suppression of class II HDACs in the salinity stress response. Collectively, our results demonstrate that HDIs that inhibit class I HDACs allow the rescue of plants from salinity stress regardless of their selectivity, and they provide insight into the hierarchal regulation of environmental stress responses through HDAC isoforms.
  • Huong Mai Nguyen; Kaori Sako; Akihiro Matsui; Yuya Suzuki; Mohammad Golam Mostofa; Chien Van Ha; Maho Tanaka; Lam-Son Phan Tran; Yoshiki Habu; Motoaki Seki
    FRONTIERS IN PLANT SCIENCE FRONTIERS MEDIA SA 8 1001  1664-462X 2017/07 [Refereed]
     
    High-salinity stress considerably affects plant growth and crop yield. Thus, developing techniques to enhance high-salinity stress tolerance in plants is important. In this study, we revealed that ethanol enhances high salinity stress tolerance in Arabidopsis thaliana and rice. To elucidate the molecular mechanism underlying the ethanol-induced tolerance, we performed microarray analyses using A. thaliana seedlings. Our data indicated that the expression levels of 1,323 and 1,293 genes were upregulated by ethanol in the presence and absence of NaCI, respectively. The expression of reactive oxygen species (ROS) signaling-related genes associated with high-salinity tolerance was upregulated by ethanol under salt stress condition. Some of these genes encode ROS scavengers and transcription factors (e.g., AtZAT10 and AtZAT12). A RT-qPCR analysis confirmed that the expression levels of AtZAT10 and AtZAT12 as well as AtAPX1 and AtAPX2, which encode cytosolic ascorbate peroxidases (APX), were higher in ethanol-treated plants than in untreated control plants, when exposure to high-salinity stress. Additionally, A. thaliana cytosolic APX activity increased by ethanol in response to salinity stress. Moreover, histochemical analyses with 3,3'-diaminobenzidine (DAB) and nitro blue tetrazolium (NBT) revealed that ROS accumulation was inhibited by ethanol under salt stress condition in A. thaliana and rice, in which DAB staining data was further confirmed by Hydrogen peroxide (H2O2) content. These results suggest that ethanol enhances high-salinity stress tolerance by detoxifying ROS. Our findings may have implications for improving salt-stress tolerance of agriculturally important field-grown crops.
  • Kazuki Kurita; Takuya Sakamoto; Noriyoshi Yagi; Yuki Sakamoto; Akihiro Ito; Norikazu Nishino; Kaori Sako; Minoru Yoshida; Hiroshi Kimura; Motoaki Seki; Sachihiro Matsunaga
    SCIENTIFIC REPORTS NATURE PUBLISHING GROUP 7 45894  2045-2322 2017/04 [Refereed]
     
    Proper regulation of histone acetylation is important in development and cellular responses to environmental stimuli. However, the dynamics of histone acetylation at the single-cell level remains poorly understood. Here we established a transgenic plant cell line to track histone H3 lysine 9 acetylation (H3K9ac) with a modification-specific intracellular antibody (mintbody). The H3K9acspecific mintbody fused to the enhanced green fluorescent protein (H3K9ac-mintbody-GFP) was introduced into tobacco BY-2 cells. We successfully demonstrated that H3K9ac-mintbody-GFP interacted with H3K9ac in vivo. The ratio of nuclear/cytoplasmic H3K9ac-mintbody-GFP detected in quantitative analysis reflected the endogenous H3K9ac levels. Under chemically induced hyperacetylation conditions with histone deacetylase inhibitors including trichostatin A, Ky-2 and Ky-14, significant enhancement of H3K9ac was detected by H3K9ac-mintbody-GFP dependent on the strength of inhibitors. Conversely, treatment with a histone acetyltransferase inhibitor, C646 caused a reduction in the nuclear to cytoplasmic ratio of H3K9ac-mintbody-GFP. Using this system, we assessed the environmental responses of H3K9ac and found that cold and salt stresses enhanced H3K9ac in tobacco BY-2 cells. In addition, a combination of H3K9ac-mintbody-GFP with 5-ethynyl-2'-deoxyuridine labelling confirmed that H3K9ac level is constant during interphase.
  • Kaori Sako; Jong-Myong Kim; Akihiro Matsui; Kotaro Nakamura; Maho Tanaka; Makoto Kobayashi; Kazuki Saito; Norikazu Nishino; Miyako Kusano; Teruaki Taji; Minoru Yoshida; Motoaki Seki
    PLANT AND CELL PHYSIOLOGY OXFORD UNIV PRESS 57 (4) 776 - 783 0032-0781 2016/04 [Refereed]
     
    Adaptation to environmental stress requires genome-wide changes in gene expression. Histone modifications are involved in gene regulation, but the role of histone modifications under environmental stress is not well understood. To reveal the relationship between histone modification and environmental stress, we assessed the effects of inhibitors of histone modification enzymes during salinity stress. Treatment with Ky-2, a histone deacetylase inhibitor, enhanced high-salinity stress tolerance in Arabidopsis. We confirmed that Ky-2 possessed inhibition activity towards histone deacetylases by immunoblot analysis. To investigate how Ky-2 improved salt stress tolerance, we performed transcriptome and metabolome analysis. These data showed that the expression of salt-responsive genes and salt stress-related metabolites were increased by Ky-2 treatment under salinity stress. A mutant deficient in AtSOS1 (Arabidopis thaliana SALT OVERLY SENSITIVE 1), which encodes an Na+/H+ antiporter and was among the up-regulated genes, lost the salinity stress tolerance conferred by Ky-2. We confirmed that acetylation of histone H4 at AtSOS1 was increased by Ky-2 treatment. Moreover, Ky-2 treatment decreased the intracellular Na+ accumulation under salinity stress, suggesting that enhancement of SOS1-dependent Na+ efflux contributes to increased high-salinity stress tolerance caused by Ky-2 treatment.
  • Jong-Myong Kim; Taku Sasaki; Minoru Ueda; Kaori Sako; Motoaki Seki
    FRONTIERS IN PLANT SCIENCE FRONTIERS MEDIA SA 6 114  1664-462X 2015/03 [Refereed]
     
    Chromatin regulation is essential to regulate genes and genome activities. In plants, the alteration of historic modification and DNA methylation are coordinated with changes in the expression of stress-responsive genes to adapt to environmental changes. Several chromatin regulators have been shown to be involved in the regulation of stress-responsive gene networks under abiotic stress conditions. Specific histone modification sites and the histone modifiers that regulate key stress responsive genes have been identified by genetic and biochemical approaches, revealing the importance of chromatin regulation in plant stress responses. Recent studies have also suggested that historic modification plays an important role in plant stress memory. In this review, we summarize recent progress on the regulation and alteration of histone modification (acetylation, methylation, phosphorylation, and SUMOylation) in response to the abiotic stresses, drought, high-salinity, heat, and cold in plants
  • Kaori Sako; Yuki Yanagawa; Tomoyuki Kanai; Takeo Sato; Motoaki Seki; Masayuki Fujiwara; Yoichiro Fukao; Junji Yamaguchi
    JOURNAL OF PROTEOME RESEARCH AMER CHEMICAL SOC 13 (7) 3223 - 3230 1535-3893 2014/07 [Refereed]
     
    The 26S proteasome is an ATP-dependent proteinase complex that is responsible for regulated proteolysis of polyubiquitinated proteins in eukaryotic cells. Here, we report novel 26S proteasome interacting proteins in Arabidopsis as revealed by LC-MS/MS analysis. We performed a two-step screening process that involved affinity purification of the 26S proteasome using Arabidopsis plants expressing a FLAG-tagged RPT2a subunit and partial purification of the 26S proteasome from cultured cells by glycerol density gradient centrifugation (GDG). Two plastid proteins, LTA2 and PDH E1 alpha, which were commonly identified by both affinity purification and GDG, interacted with the 26S proteasome both in vitro and in vivo, and the transit peptides of LTA2 and PDH E1 alpha were necessary for the interaction. Furthermore, the degradation of both LTA2 and PDH E1 alpha was inhibited by MG132, a proteasome inhibitor. Similar to those two proteins, 26S proteasome subunits RPT2a/b and RPT5a interacted with the transit peptides of three other chloroplast proteins, which are known to be substrates of the ubiquitin-26S proteasome system. These results suggest that a direct interaction between the 26S proteasome and a transit peptide is important for the degradation of unimported plastid protein precursors to maintain cellular homeostasis.
  • Takeo Sato; Kaori Sako; Junji Yamaguchi
    Methods in Molecular Biology Humana Press Inc. 1072 655 - 663 1064-3745 2014 [Refereed]
     
    The ubiquitin-26S proteasome system (UPS) plays a crucial role in selective removal of short-lived target proteins, archiving fine-tuning of post-translation levels of the target proteins. Recently a number of ubiquitin ligases (E3) have been reported as essential regulators of various plant developmental cues and stress responses. To clarify the detailed biochemical and physiological function of the E3 proteins, identification of their target proteins is of great importance. A transient expression system with tobacco leaves is a powerful method to evaluate E3 function and target degradation via UPS. Here simple methods to assay proteasome-dependent protein degradation combined with a tobacco transient expression system and detection of accumulation of ubiquitinated proteins are presented. © 2014 Springer Science+Business Media, LLC.
  • Kaori Sako; Yuko Maki; Tomoyuki Kanai; Eriko Kato; Shugo Maekawa; Shigetaka Yasuda; Takeo Sato; Masaaki K. Watahiki; Junji Yamaguchi
    PLOS ONE PUBLIC LIBRARY SCIENCE 7 (5) e37086  1932-6203 2012/05 [Refereed]
     
    The ubiquitin/proteasome pathway plays a crucial role in many biological processes. Here we report a novel role for the Arabidopsis 19S proteasome subunit RPT2a in regulating gene activity at the transcriptional level via DNA methylation. Knockout mutation of the RPT2a gene did not alter global protein levels; however, the transcriptional activities of reporter transgenes were severely reduced compared to those in the wild type. This transcriptional gene silencing (TGS) was observed for transgenes under control of either the constitutive CaMV 35S promoter or the cold-inducible RD29A promoter. Bisulfite sequencing analysis revealed that both the transgene and endogenous RD29A promoter regions were hypermethylated at CG and non-CG contexts in the rpt2a mutant. Moreover, the TGS of transgenes driven by the CaMV 35S promoters was released by treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine, but not by application of the inhibitor of histone deacetylase Trichostatin A. Genetic crosses with the DNA methyltransferase met1 single or drm1drm2cmt3 triple mutants also resulted in a release of CaMV 35S transgene TGS in the rpt2a mutant background. Increased methylation was also found at transposon sequences, suggesting that the 19S proteasome containing AtRPT2a negatively regulates TGS at transgenes and at specific endogenous genes through DNA methylation.
  • Huihui Sun; Kaori Sako; Yuya Suzuki; Shugo Maekawa; Shigetaka Yasuda; Yukako Chiba; Takeo Sato; Junji Yamaguchi
    PLANT BIOTECHNOLOGY JAPANESE SOC PLANT CELL & MOLECULAR BIOLOGY 29 (3) 279 - 284 1342-4580 2012 [Refereed]
     
    The ubiquitin/26S proteasome system (UPS) plays a central role in the degradation of short-lived regulatory proteins that control many cellular events. In this study, the Arabidopsis knockout mutant rpt2a, which contains a defect in the AtRPT2a subunit of the 26S proteasome regulatory particle, showed hypersensitivity to sugars as well as enlarged leaves. When the role of RPT2a in sugar response was examined in further detail it was found that putatively only the AtRPT2a gene of 19S proteasome was markedly transcriptionally promoted by sugar application. Notably, poly-ubiquitinated proteins degraded by the UPS accumulated significantly in rpt2a mutant under 6% sucrose conditions compared to wild type. In addition, the AtRPT2a gene in gin2, a glucose insensitive mutant with a defective glucose-sensing hexokinase, was not upregulated by sugar application, indicating that AtRPT2a is involved in hexokinase-dependent sugar response. Taken together, the above findings indicate that AtRPT2a plays an essential role in the maintenance of proteasome-dependent proteolysis activity in response to sugars.
  • Shugo Maekawa; Kaori Sako; Takeo Sato
    Seikagaku 84 (6) 416 - 424 0037-1017 2012 [Refereed]
  • Takuya Sakamoto; Takehiro Kamiya; Kaori Sako; Junji Yamaguchi; Mutsumi Yamagami; Toru Fujiwara
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY TAYLOR & FRANCIS LTD 75 (3) 561 - 567 0916-8451 2011/03 [Refereed]
     
    RPTs (regulatory particle triple-A-ATPase) are components of 26S proteasome. We found novel roles of RPT2a and RPT5a in Zn deficiency-tolerance. Arabidopsis thaliana mutants carrying T-DNA in RPT2a and RPT5a were more sensitive to Zn deficiency than the wild-type. In the;pi mutants, the shoot Zn contents were similar to those Or the wild-type. Transcripts of Zn deficiency-inducible genes were highly accumulated in the rpt mutants, suggesting that the rpt mutants suffer from various Zn deficiency symptoms, although the Zn levels are not reduced. Lipid peroxidation levels, known to be increased under Zn deficiency, were higher in the rpt mutants than in the wild-type. Poly-ubiquitinated proteins were accumulated upon exposure to Zn deficiency, especially in the rpt mutants. Overall, this study indicates that RPT2a and RPT5a are involved in Zn deficiency-tolerance, possibly through alleviation of oxidative stresses and/or processing of poly-ubiquitinated proteins.
  • Kaori Sako; Yuko Maki; Kumiko K. Imai; Takashi Aoyama; Derek B. Goto; Junji Yamaguchi
    JOURNAL OF PLANT RESEARCH SPRINGER TOKYO 123 (5) 701 - 706 0918-9440 2010/09 [Refereed]
     
    The ubiquitin/26S proteasome pathway plays a central role in the degradation of short-lived regulatory proteins to control many cellular events. The Arabidopsis knockout mutant rpt2a, which contains a defect in the AtRPT2a subunit of the 26S proteasome regulatory particle, showed enlarged leaves caused by increased cell size that correlated with increased ploidy caused by extended endoreduplication. To clarify the role of RPT2a in endoreduplication control, trichome development was genetically examined in further detail. RHL1 and GL3 encode proteins that have a role in the positive regulation of endocycle progression in trichomes. The rhl1 mutants are stalled at 8C and have trichomes with only a single branch. The rpt2a mutation did not alter the rhl1 mutant phenotype, and trichomes of double rpt2a rhl1 mutants resembled that of single rhl1 mutants. On the other hand, the rpt2a mutation suppressed the gl3 phenotype (stalled at 16C, two trichome branches), and trichomes of the double rpt2a gl3 mutant resembled those of the wild type (WT) plants. Together, these data suggest that RPT2a functions to negatively regulate endocycle progression following completion of the third endoreduplication step mediated by RHL1 (8C-16C).
  • Kaori Sako; Junji Yamaguchi
    Plant Signaling and Behavior 5 (9) 1119 - 1120 1559-2316 2010/09 [Invited]
     
    The ubiquitin/26S proteasome pathway plays a central role in the degradation of short-lived regulatory proteins to control many cellular events. The Arabidopsis genome contains two genes, AtRPT2a and AtRPT2b, which encode paralog molecules of the RPT2 subunit of 19S proteasome. We demonstrated that mutation of the AtRPT2a gene causes a specific phenotype of enlarged leaves due to increased cell size in correlation with expanded endoreduplication. This phenotype was also observed in the knockout mutant of AtRPT5a, which encodes one of the paralogs of the RPT5 subunit. Taken together, this suggests that a cell size-specific proteasome consisting of AtRPT2a and AtRPT5a is involved in controlling cell size during leaf development. © 2010 Landes Bioscience.
  • Tomokazu Tsutsui; Wataru Kato; Yutaka Asada; Kaori Sako; Takeo Sato; Yutaka Sonoda; Satoshi Kidokoro; Kazuko Yamaguchi-Shinozaki; Masanori Tamaoki; Keita Arakawa; Takanari Ichikawa; Miki Nakazawa; Motoaki Seki; Kazuo Shinozaki; Minami Matsui; Akira Ikeda; Junji Yamaguchi
    JOURNAL OF PLANT RESEARCH SPRINGER JAPAN KK 122 (6) 633 - 643 0918-9440 2009/11 [Refereed]
     
    Plants have evolved intricate mechanisms to respond and adapt to a wide variety of biotic and abiotic stresses in their environment. The Arabidopsis DEAR1 (DREB and EAR motif protein 1; At3g50260) gene encodes a protein containing significant homology to the DREB1/CBF (dehydration-responsive element binding protein 1/C-repeat binding factor) domain and the EAR (ethylene response factor-associated amphiphilic repression) motif. We show here that DEAR1 mRNA accumulates in response to both pathogen infection and cold treatment. Transgenic Arabidopsis overexpressing DEAR1 (DEAR1ox) showed a dwarf phenotype and lesion-like cell death, together with constitutive expression of PR genes and accumulation of salicylic acid. DEAR1ox also showed more limited P. syringae pathogen growth compared to wild-type, consistent with an activated defense phenotype. In addition, transient expression experiments revealed that the DEAR1 protein represses DRE/CRT (dehydration-responsive element/C-repeat)-dependent transcription, which is regulated by low temperature. Furthermore, the induction of DREB1/CBF family genes by cold treatment was suppressed in DEAR1ox, leading to a reduction in freezing tolerance. These results suggest that DEAR1 has an upstream regulatory role in mediating crosstalk between signaling pathways for biotic and abiotic stress responses.
  • Yutaka Sonoda; Kaori Sako; Yuko Maki; Naoko Yamazaki; Hiroko Yamamoto; Akira Ikeda; Junji Yamaguchi
    PLANT JOURNAL WILEY-BLACKWELL PUBLISHING, INC 60 (1) 68 - 78 0960-7412 2009/10 [Refereed]
     
    The ubiquitin/26S proteasome pathway plays a central role in the degradation of short-lived regulatory proteins, to control many cellular events. To further understand this pathway, we focused on the RPT2 subunit of the 26S proteasome regulatory particle. The Arabidopsis genome contains two genes, AtRPT2a and AtRPT2b, which encode paralog molecules of the RPT2 subunit, with a difference of only three amino acids in the protein sequences. Both genes showed similar mRNA accumulation patterns. However, the rpt2a mutant showed a specific phenotype of enlarged leaves caused by increased cell size, in correlation with increased ploidy. Detailed analyses revealed that cell expansion is increased in the rpt2a mutant by extended endoreduplication early in leaf development. The transcription of genes encoding cell cycle-related components, for DNA replication licensing and the G2/M phase, was also promoted in the rpt2a mutant, suggesting that extended endoreduplication was caused by increased DNA replication, and disrupted regulation of the G2/M checkpoint, at the proliferation stage of leaf development.
  • Yutaka Sonoda; Shan-Guo Yao; Kaori Sako; Takeo Sato; Wataru Kato; Masa-aki Ohto; Takanari Ichikawa; Minami Matsui; Junji Yamaguchi; Akira Ikeda
    PLANT JOURNAL BLACKWELL PUBLISHING 50 (4) 586 - 596 0960-7412 2007/05 [Refereed]
     
    Post-embryonic plant growth is dependent on a functional shoot apical meristem (SAM) that provides cells for continuous development of new aerial organs. However, how the SAM is dynamically maintained during vegetative development remains largely unclear. We report here the characterization of a new SAM maintenance mutant, sha1-1 (shoot apical meristem arrest 1-1), that shows a primary SAM-deficient phenotype at the adult stage. The SHA1 gene encodes a novel RING finger protein, and is expressed most intensely in the shoot apex. We show that, in the sha1-1 mutant, the primary SAM develops normally during the juvenile vegetative stage, but cell layer structure becomes disorganized after entering the adult vegetative stage, resulting in a dysfunctional SAM that cannot initiate floral primordia. The sha1-1 SAM terminates completely at the stage when the wild-type begins to bolt, producing adult plants with a primary inflorescence-deficient phenotype. These observations indicate that SHA1, a putative E3 ligase, is required for post-embryonic SAM maintenance by controlling proper cellular organization.

Books etc

MISC

Awards & Honors

  • 2018/04 理化学研究所 CSRS奨励賞
     
    受賞者: 金鍾明;Nguyen Mai Huong;佐古 香織
  • 2011/03 北海道大学 大塚賞
     
    受賞者: 佐古 香織

Research Grants & Projects

  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    Date (from‐to) : 2022/04 -2026/03 
    Author : 佐古 香織
  • 昆虫ホルモンによる植物耐塩性機構の解明
    日本学術振興会：若手研究
    Date (from‐to) : 2018 
    Author : 佐古 香織
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2017/03 
    Author : YAMAGUCHI Junji; SAKO Kaori; MAEKAWA Shugo
     
    Arabidopsis ATL31 is a membrane-localized ubiquitin ligase that functions in not only C/N-nutrient response but defense response. We identified SYP121 as a novel ATL31 interactor. SYP121 is an essential factor for plant resistance against powdery mildew fungus and positively regulates the formation of cell wall apposition, called papillae, at the fungal entry site. We finally indicated that ATL31 plays an important role in basal immunity by papilla formation through association with SYP121. The molecular basis of C/N-nutrient signaling also remains unclear. We identified three calcineurin B-like (CBL)-interacting protein kinases (CIPKs) as key regulators of the C/N-nutrient response. Further analyses showed that these CIPKs are required for ATL31 phosphorylation and stabilization, which mediates the degradation of 14-3-3 in response to C/N conditions in Arabidopsis. These findings provide new insights into C/N-nutrient signaling mediated by protein phosphorylation.
  • プロテアソームによるDNAメチル化バランス制御機構の解明
    日本学術振興会：若手研究(B)
    Date (from‐to) : 2016 
    Author : 佐古 香織

Other link

researchmap


Copyright © MEDIA FUSION Co.,Ltd. All rights reserved.