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Published Papers 【 display / non-display 】

• 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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• Evolutionary significance of the ring-like plastid nucleus in the primitive red alga Cyanidioschyzon merolae as revealed by drying.

  Kuroiwa T, Ohnuma M, Imoto Y, Yagisawa F, Misumi O, Nagata N, Kuroiwa H

  Protoplasma ( Protoplasma )  257 ( 4 ) 1069 - 1078   2020.07 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Primary plastids originated from a free-living cyanobacterial ancestor and possess their own genomes-probably a few DNA copies. These genomes, which are organized in centrally located plastid nuclei (CN-type pt-nuclei), are produced from preexisting plastids by binary division. Ancestral algae with a CN-type pt-nucleus diverged and evolved into two basal eukaryotic lineages: red algae with circular (CL-type) pt-nuclei and green algae with scattered small (SN-type) pt-nuclei. Although the molecular dynamics of pt-nuclei in green algae and plants are now being analyzed, the process of the conversion of the original algae with a CN-type pt-nucleus to red algae with a CL-type one has not been studied. Here, we show that the CN-type pt-nucleus in the primitive red alga Cyanidioschyzon merolae can be changed to the CL-type by application of drying to produce slight cell swelling. This result implies that CN-type pt-nuclei are produced by compact packing of CL-type ones, which suggests that a C. merolae-like alga was the original progenitor of the red algal lineage. We also observed that the CL-type pt-nucleus has a chain-linked bead-like structure. Each bead is most likely a small unit of DNA, similar to CL-type pt-nuclei in brown algae. Our results thus suggest a C. merolae-like alga as the candidate for the secondary endosymbiont of brown algae.

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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

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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(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)

• Uneven distribution of organelle proteins during binary fission of Cyanidioschyzon merolae

  Grant-in-Aid for challenging Exploratory Research

  Project Year: 2016.04  -  2018.03 

  Investigator(s): YAGISAWA Fumi, FUJIWARA Takayuki 

  Direct: 2,900,000 (YEN)  Overheads: 3,770,000 (YEN)  Total: 870,000 (YEN)

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  Eukaryotic cells such as animal stem cells and budding yeast divide into two daughter cells with different life spans. In these cells, organelle distribution is asymmetric regarding its quality; for example, young mitochondria are selectively distributed to cells with longer life spans. Such asymmetrical sorting of organelles is considered to be important for maintaining stemness, keeping one daughter cell young. In this project, we addressed whether similar phenomena may exist in cells that apparently divide symmetrically. Using the unicellular red alga Cyanidioschyzon merolae that proliferates through binary fission, we found that peroxisome inheritance is asymmetrical in terms of its quality. We also developed molecular tools to elucidate mechanisms associated with this phenomenon.

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