Faculty of Medicine School of Medicine Department of Infectious Diseases, Parasitology


Assistant Professor

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Papers 【 display / non-display

  • Stage-specific transcriptome of Bursaphelenchus xylophilus reveals temporal regulation of effector genes and roles of the dauer-like stages in the lifecycle Reviewed

    Tanaka S., Dayi M., Maeda Y., Tsai I., Tanaka R., Bligh M., Takeuchi-Kaneko Y., Fukuda K., Kanzaki N., Kikuchi T.

    Scientific Reports   9 ( 1 )   6080   2019.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Scientific Reports  

    © 2019, The Author(s). The pine wood nematode Bursaphelenchus xylophilus is the causal agent of pine wilt disease, one of the most devastating forest diseases in East Asian and West European countries. The lifecycle of B. xylophilus includes four propagative larval stages and gonochoristic adults which are involved in the pathogenicity, and two stages of dispersal larvae involved in the spread of the disease. To elucidate the ecological roles of each developmental stage in the pathogenic life cycle, we performed a comprehensive transcriptome analysis using RNA-seq generated from all developmental stages of B. xylophilus and compared transcriptomes between stages. We found more than 9000 genes are differentially expressed in at least one stage of the life cycle including genes involved in general nematode biology such as reproduction and moulting but also effector genes likely to be involved in parasitism. The dispersal-stage transcriptome revealed its analogy to C. elegans dauer and the distinct roles of the two larval stages from each other regarding survival and transmission. This study provides important insights and resources to understand B. xylophilus parasitic biology.

    DOI: 10.1038/s41598-019-42570-7



  • Biology and genome of a newly discovered sibling species of Caenorhabditis elegans Reviewed

    Kanzaki N., Tsai I., Tanaka R., Hunt V., Liu D., Tsuyama K., Maeda Y., Namai S., Kumagai R., Tracey A., Holroyd N., Doyle S., Woodruff G., Murase K., Kitazume H., Chai C., Akagi A., Panda O., Ke H., Schroeder F., Wang J., Berriman M., Sternberg P., Sugimoto A., Kikuchi T.

    Nature Communications   9 ( 1 )   3216   2018.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Nature Communications  

    © 2018, The Author(s). A ‘sibling’ species of the model organism Caenorhabditis elegans has long been sought for use in comparative analyses that would enable deep evolutionary interpretations of biological phenomena. Here, we describe the first sibling species of C. elegans, C. inopinata n. sp., isolated from fig syconia in Okinawa, Japan. We investigate the morphology, developmental processes and behaviour of C. inopinata, which differ significantly from those of C. elegans. The 123-Mb C. inopinata genome was sequenced and assembled into six nuclear chromosomes, allowing delineation of Caenorhabditis genome evolution and revealing unique characteristics, such as highly expanded transposable elements that might have contributed to the genome evolution of C. inopinata. In addition, C. inopinata exhibits massive gene losses in chemoreceptor gene families, which could be correlated with its limited habitat area. We have developed genetic and molecular techniques for C. inopinata; thus C. inopinata provides an exciting new platform for comparative evolutionary studies.

    DOI: 10.1038/s41467-018-05712-5



  • Assessment of the behaviour and survival of nematodes under low oxygen concentrations Reviewed

    Kitazume H., Dayi M., Tanaka R., Kikuchi T.

    PLoS ONE   13 ( 5 )   e0197122   2018.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PLoS ONE  

    © 2018 Kitazume et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Oxygen is required for the completion of almost all known metazoan lifecycles, but many metazoans harbour abilities to withstand varying degrees and periods of hypoxia. Caenorhabditis elegans, one of the most popular model organism is extensively used as a model for the study of hypoxia and anoxia biology and it has been found that this nematode is capable of tolerance to varying degrees of hypoxia. Considering the extremely high diversity of nematodes, the effects of low oxygen concentration and mechanisms of adaptation to oxygen depletion differ among species. In this study, we used a simple assay to examine anoxia tolerance in four nematode species, including three free-living and one plant parasitic nematode. We found that the plant parasitic nematode Bursaphelenchus xylophilus can survive more than 14 days under anoxic conditions. Comparisons of behaviour during anoxia induction and the repertoire of oxygen sensation genes among the tested species suggested the existence of different oxygen sensation systems between B. xylophilus and C. elegans, which quickly introduce suspended animation in response to oxygen depletion to survive long-term anoxia.

    DOI: 10.1371/journal.pone.0197122



  • Description of two three-gendered nematode species in the new genus Auanema (Rhabditina) that are models for reproductive mode evolution Reviewed

    Kanzaki N., Kiontke K., Tanaka R., Hirooka Y., Schwarz A., Müller-Reichert T., Chaudhuri J., Pires-Dasilva A.

    Scientific Reports   7 ( 1 )   11135   2017.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Scientific Reports  

    © 2017 The Author(s). The co-existence of males, females and hermaphrodites, a rare mating system known as trioecy, has been considered as an evolutionarily transient state. In nematodes, androdioecy (males/hermaphrodites) as found in Caenorhabditis elegans, is thought to have evolved from dioecy (males/females) through a trioecious intermediate. Thus, trioecious species are good models to understand the steps and requirements for the evolution of new mating systems. Here we describe two new species of nematodes with trioecy, Auanema rhodensis and A. freiburgensis. Along with molecular barcodes, we provide a detailed analysis of the morphology of these species, and document it with drawings and light and SEM micrographs. Based on morphological data, these free-living nematodes were assigned to a new genus, Auanema, together with three other species described previously. Auanema species display convergent evolution in some features with parasitic nematodes with complex life cycles, such as the production of few males after outcrossing and the obligatory development of dauers into self-propagating adults.

    DOI: 10.1038/s41598-017-09871-1



  • Genome-Wide Analyses of Individual Strongyloides stercoralis (Nematoda: Rhabditoidea) Provide Insights into Population Structure and Reproductive Life Cycles

    Kikuchi T., Hino A., Tanaka T., Aung M., Afrin T., Nagayasu E., Tanaka R., Higashiarakawa M., Win K., Hirata T., Htike W., Fujita J., Maruyama H.

    PLoS Neglected Tropical Diseases   10 ( 12 )   e0005253   2016.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:PLoS Neglected Tropical Diseases  

    © 2016 Kikuchi et al. The helminth Strongyloides stercoralis, which is transmitted through soil, infects 30–100 million people worldwide. S. stercoralis reproduces sexually outside the host as well as asexually within the host, which causes a life-long infection. To understand the population structure and transmission patterns of this parasite, we re-sequenced the genomes of 33 individual S. stercoralis nematodes collected in Myanmar (prevalent region) and Japan (non-prevalent region). We utilised a method combining whole genome amplification and next-generation sequencing techniques to detect 298,202 variant positions (0.6% of the genome) compared with the reference genome. Phylogenetic analyses of SNP data revealed an unambiguous geographical separation and sub-populations that correlated with the host geographical origin, particularly for the Myanmar samples. The relatively higher heterozygosity in the genomes of the Japanese samples can possibly be explained by the independent evolution of two haplotypes of diploid genomes through asexual reproduction during the auto-infection cycle, suggesting that analysing heterozygosity is useful and necessary to infer infection history and geographical prevalence.

    DOI: 10.1371/journal.pntd.0005253



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Books 【 display / non-display

  • 生き物と音の辞典

    高梨 琢磨 他( Role: Joint author ,  線虫の振動受容)

    朝倉書店  2019.9 

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    Total pages:441   Responsible for pages:336-337   Language:Japanese Book type:Scholarly book


Presentations 【 display / non-display

  • オオバイヌビワ果実内部の線虫の動態

    田中龍聖,Afrin tanzila,菊地泰生

    2018 日本線虫学会大会   (熊本)  日本線虫学会

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    Event date: 2018.9.5 - 2018.9.6

    Language:Japanese   Presentation type:Oral presentation (general)  


  • イチジク果実内部に生息する線虫Caenorhabdits sp. 34 の餌としての細菌



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    Event date: 2016.9.14 - 2016.9.16

    Language:Japanese   Presentation type:Oral presentation (general)  

  • Ecology of Caenorhabditis sp. 34 International conference

    Ryusei Tanaka and Taisei Kikuchi

    European Society of Nematologists 

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    Event date: 2016.8.28 - 2016.9.1

    Language:English   Presentation type:Oral presentation (general)  

  • Morphology and Ecology of fig fruits nematode Caenorhabditis sp. 34 International conference

    Ryusei Tanaka, Asako Sugimoto, Natsumi Kanzaki and Taisei Kikuchi

    Evolutionary Biology of Caenorhabditis and Other Nematodes 

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    Event date: 2016.3.30 - 2016.4.2

    Language:English   Presentation type:Poster presentation  

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

  • イチジク果実内の生物群の共進化

    2016.04 - 2019.03

    科学研究費補助金  若手研究(B)

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    Authorship:Principal investigator