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Published Papers 【 display / non-display 】

• Development of a rapamycin-inducible protein-knockdown system in the unicellular red alga Cyanidioschyzon merolae.

  Fujiwara T, Hirooka S, Yamashita S, Yagisawa F, Miyagishima SY

  Plant physiology ( Oxford University Press (OUP) )    2024.06 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Abstract An inducible protein-knockdown system is highly effective for investigating the functions of proteins and mechanisms essential for the survival and growth of organisms. However, this technique is not available in photosynthetic eukaryotes. The unicellular red alga Cyanidioschyzon merolae possesses a very simple cellular and genomic architecture and is genetically tractable but lacks RNA interference machinery. In this study, we developed a protein-knockdown system in this alga. The constitutive system utilizes the destabilizing activity of the FK506-binding protein 12 (FKBP12)-rapamycin-binding (FRB) domain of human target of rapamycin kinase or its derivatives to knock down target proteins. In the inducible system, rapamycin treatment induces the heterodimerization of the human FRB domain fused to the target proteins with the human FKBP fused to S-phase kinase-associated protein 1 or Cullin 1, subunits of the SCF E3 ubiquitin ligase. This results in the rapid degradation of the target proteins through the ubiquitin-proteasome pathway. With this system, we successfully degraded endogenous essential proteins such as the chloroplast division protein dynamin-related protein 5B and E2 transcription factor, a regulator of the G1/S transition, within 2 to 3 h after rapamycin administration, enabling the assessment of resulting phenotypes. This rapamycin-inducible protein-knockdown system contributes to the functional analysis of genes whose disruption leads to lethality.

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• Complete mitochondrial and chloroplast DNA sequences of the freshwater green microalga Medakamo hakoo.

  Takusagawa, M., Misumi, O., Nozaki, H., Kato, S., Maruyama, S., Tsujimoto-Inui, Y., Yagisawa, F., Ohnuma, M., Kuroiwa, H., Kuroiwa, T. and Matsunaga, S.

  Genes & Genetic Systems     2024.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Genomic analysis of an ultrasmall freshwater green alga, Medakamo hakoo.

  Kato S, Misumi O, Maruyama S, Nozaki H, Tsujimoto-Inui Y, Takusagawa M, Suzuki S, Kuwata K, Noda S, Ito N, Okabe Y, Sakamoto T, Yagisawa F, Matsunaga TM, Matsubayashi Y, Yamaguchi H, Kawachi M, Kuroiwa H, Kuroiwa T, Matsunaga S

  Communications biology ( Springer Science and Business Media LLC )  6 ( 1 ) 89   2023.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Abstract Ultrasmall algae have attracted the attention of biologists investigating the basic mechanisms underlying living systems. Their potential as effective organisms for producing useful substances is also of interest in bioindustry. Although genomic information is indispensable for elucidating metabolism and promoting molecular breeding, many ultrasmall algae remain genetically uncharacterized. Here, we present the nuclear genome sequence of an ultrasmall green alga of freshwater habitats, Medakamo hakoo. Evolutionary analyses suggest that this species belongs to a new genus within the class Trebouxiophyceae. Sequencing analyses revealed that its genome, comprising 15.8 Mbp and 7629 genes, is among the smallest known genomes in the Viridiplantae. Its genome has relatively few genes associated with genetic information processing, basal transcription factors, and RNA transport. Comparative analyses revealed that 1263 orthogroups were shared among 15 ultrasmall algae from distinct phylogenetic lineages. The shared gene sets will enable identification of genes essential for algal metabolism and cellular functions.

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• Complete Mitochondrial and Plastid DNA Sequences of the Freshwater Green Microalga Medakamo hakoo

  Mari Takusagawa, Shoichi Kato, Sachihiro Matsunaga, Shinichiro Maruyama, Yayoi Tsujimoto-Inui, Hisayoshi Nozaki, Fumi Yagisawa, Mio Ohnuma, Haruko Kuroiwa, Tsuneyoshi Kuroiwa, Osami Misumi

  bioRxiv ( Cold Spring Harbor Laboratory )    2021.07

  Type of publication: Research paper (scientific journal)

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  <jats:p>Here we report the complete organellar genome sequences of <jats:italic>Medakamo hakoo</jats:italic>, a green alga identified in freshwater in Japan. It has 90.8-kb plastid and 36.5-kb mitochondrial genomes containing 80 and 33 putative protein coding genes, respectively, representing the smallest organellar genome among currently known core Trebouxiophyceae.</jats:p>

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• Smooth Loop-Like Mitochondrial Nucleus in the Primitive Red Alga <i>Cyanidioschyzon merolae</i> Revealed by Drying Treatment

  Kuroiwa Tsuneyoshi, Yagisawa Fumi, Fujiwara Takayuki, Misumi Osami, Nagata Noriko, Imoto Yuuta, Yoshida Yamato, Mogi Yuko, Miyagishima Shin-ya, Kuroiwa Haruko

  ＣＹＴＯＬＯＧＩＡ ( 公益財団法人 日本メンデル協会 )  86 ( 1 ) 89 - 96   2021.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  <p>It is thought that mitochondria were generated by the symbiosis of autonomous α-proteobacteria and a eukaryote-like organism derived from an archaeon of the species <i>Sulfolobus</i>. Soon after the symbiosis, most of the genome of the α-proteobacterium, which was required for autonomy, was lost. Many genes were transferred into the host genome. However, a small amount of DNA—the mitochondrial genome (mt-genome, mtDNA)—remained in the symbiotic organelle. The primitive eukaryotic cells increased the mtDNA copy number and formed a mitochondrial nucleus (mt-nucleus). The primitive unicellular eukaryote evolved into organisms with one mitochondrion containing multiple mtDNA copies per cell, and organisms with multiple mitochondria with a small number of mtDNA copies in each cell. There have been many studies on the mitochondria and mt-genomes of amoeba, plants, and animals which contain many mitochondria per cell, but only a few studies have reported morphological characteristics of the mitochondria and their genomes in primitive unicellular organisms that have only a single mitochondrion per cell. Here, we show that centrally located mt-nuclei in the primitive red alga <i>Cyanidioschyzon merolae</i> form smooth rings following the application of a drying method that produces slight cell swelling. We discuss regulatory mechanisms for genome function in endosymbiotic organelles on the basis of the differences between the copy number of mtDNA in smooth-ring shaped mt-nuclei and plastid DNA in bead-shaped plastid nuclei.</p>

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Books 【 display / non-display 】

Books 【 display / non-display 】

• Cyanidioschyzon merolae: A New Model Eukaryote for Cell and Organelle Biology

  Yagisawa F, Imoto Y, Fujiwara T, Miyagishima S ( Part: Multiple Authorship ,  16. Single-Membrane-Bound organelles: Division and Inheritance )

  Springer  2018.02

Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2022.04  -  2025.03 

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,200,000 (YEN)  Overheads: 960,000 (YEN) 

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,200,000 (YEN)  Overheads: 4,160,000 (YEN)  Total: 960,000 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2019.04  -  2022.03 

  Direct: 13,100,000 (YEN)  Overheads: 3,930,000 (YEN)  Total: 17,030,000 (YEN)

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2019.04  -  2022.03 

  Direct: 3,300,000 (YEN)  Overheads: 4,290,000 (YEN)  Total: 990,000 (YEN)

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