論文 - 田中 龍聖
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Ryusei Tanaka, Natsumi Kanzaki, Robin M. Giblin-Davis
Nematology 27 ( 1 ) 37 - 48 2024年11月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Nematology
Schistonchus pumilae was first reported from the syconi of a creeper fig, Ficus pumila, from Miyazaki, Japan, and the species was described based on propagative (plant-parasitic) females and males. Thus, the premature female (entomophilic form) of the species was not described. In the present study, male syconi of F. pumila were collected from the type locality of the nematode (Miyazaki, Japan), and the premature females of S. pumilae were collected from inside the syconi and also from the emerging pollinator fig wasps (Wiebesia pumilae). Although only 26 female wasps were recovered for dissections, seven of them harboured 1-7 nematodes each. Nematodes associated with the wasp were all premature females, and their typological and morphometric characters were similar with those isolated from inside the syconi. In addition, the premature females were slightly smaller than propagative females and had a less developed gonad, suggesting that the nematode is a phoretic associate, not a parasite. Regardless of its phylogenetic status, the carrier insect usage of S. pumilae is somewhat similar to two Ficophagus species, and clearly different from S. caprifici, which propagates in the host wasp haemocoel as a parasite. Additionally, the molecular profiles of S. pumilae (SSU and D1-D3 LSU of ribosomal RNA genes) were re-sequenced using a cloning technique, and the information was updated for phylogenetic analysis in the future.
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Kawahara K, Inada T, Tanaka R, Dayi M, Makino T, Maruyama S, Kikuchi T, Sugimoto A, Kawata M
Genome biology and evolution 15 ( 4 ) 2023年4月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Genome biology and evolution
Why the recently discovered nematode Caenorhabditis inopinata differs so greatly from its sibling species Caenorhabditis elegans remains unknown. A previous study showed that C. inopinata has more transposable elements (TEs), sequences that replicate and move autonomously throughout the genome, potentially altering the expression of neighboring genes. In this study, we focused on how the body size of this species has evolved and whether TEs could affect the expression of genes related to species-specific traits such as body size. First, we compared gene expression levels between C. inopinata and C. elegans in the L4 larval and young adult stages-when growth rates differ most prominently between these species-to identify candidate genes contributing to their differences. The results showed that the expression levels of collagen genes were consistently higher in C. inopinata than in C. elegans and that some genes related to cell size were differentially expressed between the species. Then, we examined whether genes with TE insertions are differentially expressed between species. Indeed, the genes featuring C. inopinata-specific TE insertions had higher expression levels in C. inopinata than in C. elegans. These upregulated genes included those related to body size, suggesting that these genes could be candidates for artificial TE insertion to examine the role of TEs in the body size evolution of C. inopinata.
DOI： 10.1093/gbe/evad063
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Ko P.P., Haraguchi M., Hara T., Hieu D.D., Ito A., Tanaka R., Tanaka M., Suzumura T., Ueda M., Yoshida A., Maruyama H., Nagayasu E.
Parasitology International 92 102663 2023年2月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Parasitology International
Strongyloides is a genus of parasitic nematodes of vertebrates comprising approximately 50 documented species, each with various host ranges. Among these, three species (S. stercoralis, S. fuelleborni, and S. cebus) are known to infect primate hosts. S. fuelleborni typically infects non-human primates in the Old World. To complement the existing information on the global genetic structure of this species, we conducted a genotyping study of S. fuelleborni samples collected from rhesus macaques in Myanmar, Japanese macaques in Japan, and some zoo-kept primates. This study identified a novel haplotype group in isolates from the Myanmar rhesus macaques. Subsequently, we obtained the complete or nearly complete mitochondrial genome sequences of S. fuelleborni, S. cebus (Strongyloides of New World monkeys), and S. vituli (Strongyloides of cattle). Phylogenetic analysis based on concatenated mitochondrial protein sequences of various Strongyloides species indicated a close relationship between S. fuelleborni, S. vituli and S. papillosus (Strongyloides in sheep and cattle). S. cebus is quite distantly related to both S. fuelleborni and S. stercoralis, which led to the hypothesis that the three primate Strongyloides species evolved independently as parasites of primates.
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Kanzaki N., Tanaka R., Giblin-Davis R.M.
Nematology 25 ( 5 ) 509 - 529 2023年
掲載種別：研究論文（学術雑誌） 出版者・発行元：Nematology
A Schistonchus species was isolated from the syconia of the creeping fig, Ficus pumila, collected from Miyazaki, Japan. The nematode was considered an undescribed species based on its typological characters, molecular profiles (near full length of small subunit and D3 expansion segment of large subunit of RNA) and phylogenetic status inferred from these two loci. The new species is characterised by the presence of flagellate sperm, spicule possessing small condylus, triangular rostrum with bluntly pointed tip and clear dorsal and ventral limbs, structure and arrangement of male caudal papillae, i.e., presence of papilliform P3 and P3a and small and gland opening-like P4 (glandpapillae), relatively short post-uterine sac and female tail forming elongate conoid. It is phylogenetically close to S. hirtus. However, the new species is distinguished from other nominal Schistonchus species by its female tail shape forming elongate conoid, the structure and arrangement of male caudal papillae and several other typological characters. In addition, the host fig of the nematode, F. pumila, is a creeper fig species belonging to subgenus Synoecia (section Rhizocladus; subsection Plagiostigma), from which no fig-Associated nematode has been reported so far, i.e., the present study is the first report of Schistonchus (and other syconia-inhabiting nematodes) from the Ficus subgenus Synoecia. Keywords
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Sun S., Kanzaki N., Dayi M., Maeda Y., Yoshida A., Tanaka R., Kikuchi T.
BMC Genomics 23 ( 1 ) 765 2022年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：BMC Genomics
Background: The first metazoan genome sequenced, that of Caenorhabditis elegans, has motivated animal genome evolution studies. To date > 50 species from the genus Caenorhabditis have been sequenced, allowing research on genome variation. Results: In the present study, we describe a new gonochoristic species, Caenorhabditis niphades n. sp., previously referred as C. sp. 36, isolated from adult weevils (Niphades variegatus), with whom they appear to be tightly associated during its life cycle. Along with a species description, we sequenced the genome of C. niphades n. sp. and produced a chromosome-level assembly. A genome comparison highlighted that C. niphades n. sp. has the smallest genome (59 Mbp) so far sequenced in the Elegans supergroup, despite being closely related to a species with an exceptionally large genome, C. japonica. Conclusions: The compact genome of C. niphades n. sp. can serve as a key resource for comparative evolutionary studies of genome and gene number expansions in Caenorhabditis species.
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ノキシノブ葉面から分離された菌類
柴田 紗帆, 岸本 圭子, 田中 龍聖, 竹本 周平, 廣岡 裕吏
日本森林学会大会発表データベース 133 ( 0 ) 639 2022年5月
記述言語：日本語 掲載種別：研究論文（研究会，シンポジウム資料等） 出版者・発行元：日本森林学会
葉の表面を指す葉面（phylloplane）は，陸上微生物最大の生息場所の1つと考えられている．この葉面上には，植物を基質とする菌類だけでなく，葉面上の他の生物，花粉や塵といった堆積物などを基質とする多様な菌類種が存在すると考えられている．しかしながら，葉面に存在する菌類（葉面菌）は胞子や酵母，菌糸などの単純な形態で存在することや，その単純な形態ゆえに種同定が極めて難しいことから，生態学的役割について未解明な点が多い．そこで本研究では，葉面菌の生態学的役割解明に向けたそれら菌の同定基盤の構築を目指し，林内で容易に観察されるノキシノブ（常緑シダ植物の一種）の葉面より分離された菌類の多様性解明を行なった．異なる地域や時期に採取したノキシノブ71標本の葉面から420菌株を分離し，rDNA LSU領域の塩基配列を用いてそれら菌株の簡易同定を行なった．そして，そのうち分離頻度の高い17種について，詳細な種同定を行った結果，約半数にあたる8種は未記載種と考えられた．今後，葉面菌の生態学的役割を明らかにするためには，これら多様な菌類のさらなる分類学的研究が必要である．
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Dayi M., Kanzaki N., Sun S., Ide T., Tanaka R., Masuya H., Okabe K., Kajimura H., Kikuchi T.
Scientific Reports 11 ( 1 ) 6720 2021年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Scientific Reports
Caenorhabditis auriculariae, which was morphologically described in 1999, was re-isolated from a Platydema mushroom-associated beetle. Based on the re-isolated materials, some morphological characteristics were re-examined and ascribed to the species. In addition, to clarify phylogenetic relationships with other Caenorhabditis species and biological features of the nematode, the whole genome was sequenced and assembled into 109.5 Mb with 16,279 predicted protein-coding genes. Molecular phylogenetic analyses based on ribosomal RNA and 269 single-copy genes revealed the species is closely related to C. sonorae and C. monodelphis placing them at the most basal clade of the genus. C. auriculariae has morphological characteristics clearly differed from those two species and harbours a number of species-specific gene families, indicating its usefulness as a new outgroup species for Caenorhabditis evolutionary studies. A comparison of carbohydrate-active enzyme (CAZy) repertoires in genomes, which we found useful to speculate about the lifestyle of Caenorhabditis nematodes, suggested that C. auriculariae likely has a life-cycle with tight-association with insects.
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Nearly complete genome assembly of the pinewood nematode bursaphelenchus xylophilus strain Ka4C1 査読あり 国際共著
Dayi M., Sun S., Maeda Y., Tanaka R., Yoshida A., Tsai I.J., Kikuchi T.
Microbiology Resource Announcements 9 ( 42 ) 2020年10月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Microbiology Resource Announcements
Bursaphelenchus xylophilus has been destroying pine forests in East Asia and western Europe. Here, we report its nearly complete genomic sequence containing five ;12-Mb scaffolds and one ∼15-Mb scaffold representing six chromosomes. Large repeat regions that were previously unidentified are now reasonably integrated, particularly in the ∼15-Mb scaffold.
DOI： 10.1128/MRA.01002-20
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井龍 友美, 田中 龍聖, 吉賀 豊司
日本線虫学会誌 50 ( 1 ) 1 - 7 2020年9月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：日本線虫学会
シヘンチュウは様々な無脊椎動物の寄生虫であるが、その宿主と関係する生活史についての情報は限られている。我々は一化性で定着性のベニツチカメムシから分離されたシヘンチュウについて、生活環と寄生が宿主に及ぼす影響について調査した。シヘンチュウは6カ所中5カ所の採集場所で検出され、寄生率は0％から16％だった。多くの場合は単寄生だったが重寄生もみられた。シヘンチュウは終齢若虫から離脱し、宿主は離脱後にすぐに死亡した。本調査では、成虫からの離脱は観察されなかった。宿主とシヘンチュウの体重の間には相関はみられなかった。寄生の有無によって宿主の生体重や形態的・行動的変化はなく、離脱までは宿主は影響を受けないことが示唆された。系統解析によって、佐賀エリアのみ、および全ての異なるベニツチカメムシ個体群から検出される、2種類のシヘンチュウが存在することが明らかとなった。
DOI： 10.3725/jjn.50.1
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Mondal S.I., Akter A., Koga R., Hosokawa T., Dayi M., Murase K., Tanaka R., Shigenobu S., Fukatsu T., Kikuchi T.
Frontiers in Microbiology 11 840 2020年5月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Frontiers in Microbiology
Diverse animals, including insects, harbor microbial symbionts within their gut, body cavity, or cells. The subsocial parastrachiid stinkbug Parastrachia japonensis is well-known for its peculiar ecological and behavioral traits, including its prolonged non-feeding diapause period and maternal care of eggs/nymphs in an underground nest. P. japonensis harbors a specific bacterial symbiont within the gut cavity extracellularly, which is vertically inherited through maternal excretion of symbiont-containing white mucus. Thus far, biological roles of the symbiont in the host lifecycle has been little understood. Here we sequenced the genome of the uncultivable gut symbiont “Candidatus Benitsuchiphilus tojoi.” The symbiont has an 804 kb circular chromosome encoding 606 proteins and a 14.5 kb plasmid encoding 13 proteins. Phylogenetic analysis indicated that the bacterium is closely related to other obligate insect symbionts belonging to the Gammaproteobacteria, including Buchnera of aphids and Blochmannia of ants, and the most closely related to Ishikawaella, an extracellular gut symbiont of plataspid stinkbugs. These data suggested that the symbiont genome has evolved like highly reduced gamma-proteobacterial symbiont genomes reported from a variety of insects. The presence of genes involved in biosynthesis pathways for amino acids, vitamins, and cofactors in the genome implicated the symbiont as a nutritional mutualist, supplementing essential nutrients to the host. Interestingly, the symbiont’s plasmid encoded genes for thiamine and carotenoid synthesis pathways, suggesting the possibility of additional functions of the symbiont for protecting the host against oxidative stress and DNA damage. Finally, possible involvement of the symbiont in uric acid metabolism during diapause is discussed.
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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年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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Biology and genome of a newly discovered sibling species of Caenorhabditis elegans 査読あり 国際共著
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年12月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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Assessment of the behaviour and survival of nematodes under low oxygen concentrations 査読あり 国際共著
Kitazume H., Dayi M., Tanaka R., Kikuchi T.
PLoS ONE 13 ( 5 ) e0197122 2018年5月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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Kanzaki N., Kiontke K., Tanaka R., Hirooka Y., Schwarz A., Müller-Reichert T., Chaudhuri J., Pires-Dasilva A.
Scientific Reports 7 ( 1 ) 11135 2017年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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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年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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Genome-Wide Analyses of Individual Strongyloides stercoralis (Nematoda: Rhabditoidea) Provide Insights into Population Structure and Reproductive Life Cycles 査読あり
Taisei Kikuchi , Akina Hino , Teruhisa Tanaka , Myo Pa Pa Thet Hnin Htwe Aung,Tanzila Afrin, Eiji Nagayasu, Ryusei Tanaka, Miwa Higashiarakawa, Kyu Kyu Win, Tetsuo Hirata,Wah Win Htike, Jiro Fujita,Haruhiko Maruyama
PLOS Neglected Tropical Diseases 2016年12月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Venison, another source of Paragonimus westermani infection 査読あり
Yoshida A., Matsuo K., Moribe J., Tanaka R., Kikuchi T., Nagayasu E., Misawa N., Maruyama H.
Parasitology International 65 ( 6 ) 607 - 612 2016年12月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Parasitology International
© 2016 Elsevier Ireland Ltd Paragonimiasis is a typical food-borne parasitic disease, endemic in most parts of Asia, with sporadic case reports from American and African countries. The major source of infection is undercooked freshwater crab or crayfish, though consumption of wild boar meat is also responsible for the infection in Japan, because wild boar is a paratenic host for Paragonimus westermani. Recently, living juveniles of P. westermani were isolated from muscle of a sika deer, Cervus nippon, in Japan, raising the possibility that venison has been another source of infection. In order to clarify the potential contribution of venison consumption to the occurrence of paragonimiasis, we analysed dietary histories of those paragonimiasis patients in whose diagnoses we were involved between 2001 and 2015. Among 380 patients, freshwater crab had been consumed by 208 patients, wild boar meat by 190, and wild deer meat by 76 patients before the onset of the disease. Overall contribution of wild deer meat was estimated to be 6.8% to 20.0%, although in Oita and Gifu Prefectures, where a substantial proportion of patients had consumed raw venison, the contribution of venison consumption was much higher (27.5 to 62.1% and 42.1 to 78.9% in Oita and Gifu Prefectures, respectively). We demonstrated P. westermani-specific antibodies in the sera of 4 out of 160 sika deer from Gifu Prefecture, strongly suggesting that these deer were infected with P. westermani.
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Venison, another source of Paragonimus westermani infection 査読あり
Yoshida A, Matsuo K, Moribe J, Tanaka R, Kikuchi T, Nagayasu E, Misawa N, Maruyama H.
Parasitology International 2016年12月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Tsai I., Tanaka R., Kanzaki N., Akiba M., Yokoi T., Espada M., Jones J., Kikuchi T.
Molecular Plant Pathology 17 ( 1 ) 77 - 83 2016年1月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Molecular Plant Pathology
© 2016 BSPP and John Wiley & Sons Ltd. Summary: Drastic physiological and morphological changes in parasites are crucial for the establishment of a successful infection. The nematode Bursaphelenchus xylophilus is the pathogenic agent of pine wilt disease, and little is known about the physiology and morphology in this nematode at the initial stage of infection. In this study, we devised an infection system using pine stem cuttings that allowed us to observe transcriptional and morphological changes in the host-infecting phytophagous phase. We found that 60 genes enriched in xenobiotic detoxification were up-regulated in two independent post-inoculation events, whereas down-regulation was observed in multiple members of collagen gene families. After 48h of inoculation, the tails in some of the adult females exposed to the host changed in morphology. These results suggest that B.xylophilus may change its physiology and morphology to protect itself and to adapt to the host pine wood environment.
DOI： 10.1111/mpp.12261
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田中 克, 田中 龍聖, 竹内 祐子, 神崎 菜摘, 菊地 泰生, 福田 健二
日本森林学会大会発表データベース 127 ( 0 ) 2016年
記述言語：日本語 掲載種別：研究論文（研究会，シンポジウム資料等） 出版者・発行元：日本森林学会
マツノザイセンチュウは東アジアや西ヨーロッパで甚大な被害を及ぼすマツ材線虫病（以下マツ枯れ）の病原体である。本線虫は増殖型と分散型の二型性の生活環を持ち、増殖型はマツの衰弱・枯死に関与する一方、分散型はマツ枯れ伝播に関与する。特に分散型IV期幼虫（以下D<sub>IV</sub>）は、媒介昆虫であるマツノマダラカミキリからの誘導を受けて出現し、マツからマツへと運ばれるため、疫学上重要な役割を担う。本研究ではD<sub>IV</sub>の生理的機能を遺伝子発現の面から解明するため、RNA-seq法を用いた線虫全ステージの比較解析を行い、D<sub>IV</sub>で特徴的な発現を示す遺伝子の同定を試みた。その結果、線虫全ステージ合計で15,251遺伝子、D<sub>IV</sub>では12,730遺伝子の発現が確認された。D<sub>IV</sub>は、増殖型各ステージと比較して774~3,448遺伝子（約5~21%）の発現が有意に異なった。また、D<sub>IV</sub>の前段階である分散型III期幼虫との比較においても、2,347遺伝子（約14%）の発現が有意に異なった。これらのことから、D<sub>IV</sub>が形態や生態だけでなく遺伝子発現においても特徴的であることが明らかとなった。講演では上記の遺伝子の機能も含めて、D<sub>IV</sub>の遺伝子発現様式を総合的に論じる。