博士（生命科学）, 北海道大学

Mar. 2022, 北海道大学, 大塚賞

Sep. 2021, 日本植物バイオテクノロジー学会, 学生奨励賞
栄養シグナルによる植物成長制御に関わる転写因子の機能解明

Cellular energy sensor SnRK1 suppresses salicylic acid-dependent and -independent defenses and bacterial resistance in Arabidopsis.
Linnan Jie; Miho Sanagi; Shigetaka Yasuda; Kohji Yamada; Saki Ejima; Ayumi Sugisaki; Junpei Takagi; Mika Nomoto; Xiu-Fang Xin; Yasuomi Tada; Yusuke Saijo; Takeo Sato
Proceedings of the National Academy of Sciences of the United States of America, 122, 48, e2527765122, 02 Dec. 2025, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, In nature, plants cope with various pathogens that compete for cellular resources during infection. It has long been suggested that plant defense activity must be linked to cellular energy and metabolic states to optimize the balance between growth and defense. However, the molecular mechanisms that regulate immune activity in relation to cellular energy status remain unclear. Here, we demonstrate that the plant energy sensor SNF1-RELATED KINASE 1 (SnRK1) plays a critical role in modulating defense responses and bacterial resistance in Arabidopsis thaliana. Bacterial elicitor-induced expression of defense marker genes, such as PATHOGENESIS-RELATED 1 (PR1), is significantly repressed under sugar-limited conditions in wild-type seedlings, whereas this expression is markedly enhanced in the snrk1α1i/α2 knockdown mutants. SnRK1 restricts defense-related gene expression and resistance to the biotrophic bacterial pathogen Pseudomonas syringae pv. tomato DC3000, which are partly dependent on salicylic acid (SA). In addition, we found that the SnRK1 kinase activity is increased by high humidity. Consistently, SnRK1 is critical for the suppression of SA-mediated defense responses under high humidity conditions. SnRK1 physically associates with the SA-related transcription factors TGACG SEQUENCE-SPECIFIC BINDING PROTEIN 4 (TGA4) and TGA2 to attenuate PR1 expression. These findings provide valuable insight into the molecular mechanisms linking cellular energy status with immune regulation in plants.

New insights into nutrient- and drought-responsive flowering.
Miho Sanagi; Filip Rolland; Takeo Sato
Journal of experimental botany, 77, 5, 1362, 1374, 28 Mar. 2025, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, Nutrients not only provide energy and structural components but also play essential roles as regulatory molecules to control plant growth and development. Flowering is a key developmental phase transition (from vegetative to reproductive growth), and its precise timing determines reproductive fitness and crop yield. This requires coordination of metabolism, partitioning between source and sink tissues, and apical meristem activity with nutrient supplies. Here we summarize recent advances in our understanding of nutrient-regulated flowering, focusing on sugars and the three primary (soil supplied) macronutrients nitrogen, phosphorus, and potassium, also considering drought stress as a highly relevant condition affecting nutrient availability. Most notably, recent evidence indicates that the evolutionarily conserved SNF1-RELATED KINASE 1 (SnRK1) kinase, a key metabolic sensor, serves as an integrator of nutrient status to control flowering. However, the combined effects of multiple nutrients on flowering and differences in responses between plant species remain underexplored and are an important topic for future research.

Citrate pretreatment promotes rice (Oryza sativa L.) coleoptile elongation under submergence
Akio Kubo; Miho Sanagi; Yuko Maki; Ryosuke Koyari; Futoshi Sakuma; Junji Yamaguchi; Takeo Sato
Plant Biotechnology, 42, 1, 57, 64, Japanese Society for Plant Cell and Molecular Biology, 25 Mar. 2025, [Peer-reviewed]
Scientific journal

Histone chaperone NUCLEOSOME ASSEMBLY PROTEIN 1 proteins affect plant growth under nitrogen deficient conditions in Arabidopsis thaliana
Linnan Jie; Miho Sanagi; Yongming Luo; Haruna Maeda; Yoichiro Fukao; Yukako Chiba; Shuichi Yanagisawa; Junji Yamaguchi; Junpei Takagi; Takeo Sato
PLANT BIOTECHNOLOGY, 40, 1, 93, 98, Mar. 2023, [Peer-reviewed]
English, Scientific journal

Low nitrogen conditions accelerate flowering by modulating the phosphorylation state of FLOWERING BHLH 4 in Arabidopsis.
Miho Sanagi; Shoki Aoyama; Akio Kubo; Yu Lu; Yasutake Sato; Shogo Ito; Mitsutomo Abe; Nobutaka Mitsuda; Masaru Ohme-Takagi; Takatoshi Kiba; Hirofumi Nakagami; Filip Rolland; Junji Yamaguchi; Takato Imaizumi; Takeo Sato
Proceedings of the National Academy of Sciences of the United States of America, 118, 19, 11 May 2021, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, Nitrogen (N) is an essential nutrient that affects multiple plant developmental processes, including flowering. As flowering requires resources to develop sink tissues for reproduction, nutrient availability is tightly linked to this process. Low N levels accelerate floral transition; however, the molecular mechanisms underlying this response are not well understood. Here, we identify the FLOWERING BHLH 4 (FBH4) transcription factor as a key regulator of N-responsive flowering in Arabidopsis Low N-induced early flowering is compromised in fbh quadruple mutants. We found that FBH4 is a highly phosphorylated protein and that FBH4 phosphorylation levels decrease under low N conditions. In addition, decreased phosphorylation promotes FBH4 nuclear localization and transcriptional activation of the direct target CONSTANS (CO) and downstream florigen FLOWERING LOCUS T (FT) genes. Moreover, we demonstrate that the evolutionarily conserved cellular fuel sensor SNF1-RELATED KINASE 1 (SnRK1), whose kinase activity is down-regulated under low N conditions, directly phosphorylates FBH4. SnRK1 negatively regulates CO and FT transcript levels under high N conditions. Together, these results reveal a mechanism by which N levels may fine-tune FBH4 nuclear localization by adjusting the phosphorylation state to modulate flowering time. In addition to its role in flowering regulation, we also showed that FBH4 was involved in low N-induced up-regulation of nutrient recycling and remobilization-related gene expression. Thus, our findings provide insight into N-responsive growth phase transitions and optimization of plant fitness under nutrient-limited conditions.

Protein Phosphorylation Dynamics Under Carbon/Nitrogen-Nutrient Stress and Identification of a Cell Death-Related Receptor-Like Kinase in Arabidopsis.
Xingwen Li; Miho Sanagi; Yu Lu; Yuko Nomura; Sara Christina Stolze; Shigetaka Yasuda; Yusuke Saijo; Waltraud X Schulze; Regina Feil; Mark Stitt; John E Lunn; Hirofumi Nakagami; Takeo Sato; Junji Yamaguchi
Frontiers in plant science, 11, 377, 377, 2020, [Peer-reviewed], [International Magazine]
English, Scientific journal, Nutrient availability, in particular the availability of sugar [carbon (C)] and nitrogen (N), is important for the regulation of plant metabolism and development. In addition to independent utilization of C and N nutrients, plants sense and respond to the balance of C and N nutrients (C/N-nutrient) available to them. High C/low N-nutrient stress has been shown to arrest early post-germinative growth while promoting progression to senescence in Arabidopsis. Although several signaling components of the C/N-nutrient response have been identified, the inclusive molecular basis of plant C/N-nutrient response remains unclear. This proteome analysis evaluated phosphorylation dynamics in response to high C/low N-nutrient stress. Phosphoproteomics under conditions of C/N-nutrient stress showed a global change in the phosphorylation status of proteins, including plasma membrane H+-ATPase, carbon and nitrogen metabolic enzymes and signaling proteins such as protein kinases and transcription factors. Further analyses suggested that SNF1-related protein kinase 1 (SnRK1) is involved in primary C/N-nutrient signal mediation via the transcriptional regulation of C/N-regulatory kinases. We also identified a leucine-rich repeat receptor-like kinase with extracellular malectin-like domain, named as LMK1, which was shown to possess cell death induction activity in plant leaves. These results provide important insight into the C/N-nutrient signaling pathways connecting nutrition stress to various cellular and physiological processes in plants.

Sugar-responsive transcription factor bZIP3 affects leaf shape in Arabidopsis plants.
Miho Sanagi; Yu Lu; Shoki Aoyama; Yoshie Morita; Nobutaka Mitsuda; Miho Ikeda; Masaru Ohme-Takagi; Takeo Sato; Junji Yamaguchi
Plant biotechnology (Tokyo, Japan), 35, 2, 167, 170, 25 Jun. 2018, [Peer-reviewed], [Lead author], [Domestic magazines]
English, Scientific journal, Sugars are essential for plant metabolism, growth and development. Plants must therefore manage their growth and developmental processes in response to sugar availability. Sugar signaling pathways constitute a complicated molecular network and are associated with global transcriptional regulation. However, the molecular mechanisms underlying sugar signaling remain largely unclear. This study reports that the protein basic-region leucine zipper 3 (bZIP3) is a novel sugar-responsive transcription factor in Arabidopsis plants. The expression of bZIP3 was rapidly repressed by sugar. Genetic analysis indicated that bZIP3 expression was modulated by the SNF1-RELATED KINASE 1 (SnRK1) pathway. Moreover, transgenic plants overexpressing bZIP3 and dominant repressor form bZIP3-SRDX showed aberrant shaped cotyledons with hyponastic bending. These findings suggest that bZIP3 plays a role in plant responses to sugars and is also associated with leaf development.

Membrane-localized ubiquitin ligase ATL15 functions in sugar-responsive growth regulation in Arabidopsis.
Shoki Aoyama; Saki Terada; Miho Sanagi; Yoko Hasegawa; Yu Lu; Yoshie Morita; Yukako Chiba; Takeo Sato; Junji Yamaguchi
Biochemical and biophysical research communications, 491, 1, 33, 39, 09 Sep. 2017, [Peer-reviewed], [International Magazine]
English, Scientific journal, Ubiquitin ligases play important roles in regulating various cellular processes by modulating the protein function of specific ubiquitination targets. The Arabidopsis Tóxicos en Levadura (ATL) family is a group of plant-specific RING-type ubiquitin ligases that localize to membranes via their N-terminal transmembrane-like domains. To date, 91 ATL isoforms have been identified in the Arabidopsis genome, with several ATLs reported to be involved in regulating plant responses to environmental stresses. However, the functions of most ATLs remain unknown. This study, involving transcriptome database analysis, identifies ATL15 as a sugar responsive ATL gene in Arabidopsis. ATL15 expression was rapidly down-regulated in the presence of sugar. The ATL15 protein showed ubiquitin ligase activity in vitro and localized to plasma membrane and endomembrane compartments. Further genetic analyses demonstrated that the atl15 knockout mutants are insensitive to high glucose concentrations, whereas ATL15 overexpression depresses plant growth. In addition, endogenous glucose and starch amounts were reciprocally affected in the atl15 knockout mutants and the ATL15 overexpressors. These results suggest that ATL15 protein plays a significant role as a membrane-localized ubiquitin ligase that regulates sugar-responsive plant growth in Arabidopsis.

Flowering regulation in response to nitrogen availability
Sanagi Miho; Sato Takeo, 生化学, 94, 6, 892, 895, 25 Dec. 2022
公益社団法人日本生化学会, Japanese

植物の細胞内エネルギーセンサーを介した環境に応じた免疫活性制御機構
科学研究費助成事業
01 Apr. 2026 - 31 Mar. 2029
佐藤 長緒; 眞木 美帆
日本学術振興会, 基盤研究(B), 北海道大学, 26K01704

転写因子によるクロマチン制御と植物栄養ストレス適応機構の解明
科学研究費助成事業
01 Apr. 2025 - 31 Mar. 2027
眞木 美帆
日本学術振興会, 若手研究, 北海道大学, 25K18208

多階層オミクスデータ統合による植物の環境に応じた成長相転換機構の解明
創成はばたく次世代研究助成事業
Jul. 2024 - Mar. 2026
北海道大学（第一三共株式会社）, Principal investigator

糖による植物免疫強化機構の解明
科学研究費助成事業
Apr. 2023 - Mar. 2026
佐藤 長緒; 眞木 美帆; 高木 純平
日本学術振興会, 基盤研究(B), 北海道大学, 23H02170

植物の栄養環境に応じた花成と代謝の協調的制御機構の解明
科学研究費助成事業 若手研究
01 Apr. 2023 - 31 Mar. 2025
眞木 美帆
日本学術振興会, 若手研究, 北海道大学, 23K13921

SnRK1-FBH4による窒素シグナルに応じた花成制御機構の解明
科学研究費助成事業 特別研究員奨励費
25 Apr. 2019 - 31 Mar. 2022
眞木 美帆
本研究では，SnRK1-FBH4による窒素栄養に応じた花成制御の分子機構解明を目指している。これまでの研究より，低窒素条件においては，転写因子FBH4タンパク質のリン酸化状態が変動すること，FBH4の標的遺伝子かつ花成制御に重要な因子であるCOとその標的遺伝子であるFT遺伝子発現が上昇していることが示唆されていた。また，真核生物に広く保存された栄養センサーであるSnRK1キナーゼが花成制御に関与することを見出していた。
当該年度は，窒素シグナルに応じたSnRK1キナーゼと転写因子FBH4リン酸化の機能に関してさらに詳細な解析を行った。研究成果として，FBH4のリン酸化状態が標的遺伝子であるCOの転写活性に影響を及ぼすことに加え，FBH4リン酸化の機能の新たな知見を得た。SnRK1キナーゼとFBH4の関係性については，in vitroにおけるリン酸化アッセイから，SnRK1がFBH4を直接的にリン酸化することを明らかにした。
さらに，植物体内において，SnRK1キナーゼの活性を評価する系の確立を試みた。レポーターとしてSnRK1がリン酸化する既知の標的ペプチドを使用し，このレポーターを発現するシロイヌナズナ株を作出した。レポーター内の標的ペプチドのリン酸化状態を検出する抗体を用いたウェスタンブロット解析を行うことで，SnRK1キナーゼの活性を評価できる。実際にこのレポーター系を用いて，窒素栄養に応じた植物内生のSnRK1キナーゼ活性を検証した。この結果は，窒素シグナルによるSnRK1の機能制御を理解する上で重要なデータとなった。
日本学術振興会, 特別研究員奨励費, 北海道大学, 19J21101