論文 - 長野 直樹
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Barnuevo K.D., Vuong N.T., Mohapatra S., Sato O., Katoh H., Itoh T., Nagano N., Matsuyama M., Chakraborty T., Ohta K.
Comparative Biochemistry and Physiology Part A Molecular and Integrative Physiology 306 111879 2025年8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：Comparative Biochemistry and Physiology Part A Molecular and Integrative Physiology
Salinity plays a crucial role in fish physiology, including osmoregulation, metabolism, growth, reproduction, and disease resistance. In this study, we characterized the Transient Receptor Potential Cation Channel Subfamily Vanilloid 4 (trpv4) gene and investigated the effects of low-salinity conditions on its expression in various tissues of chub mackerel (Scomber japonicus), an economically important aquaculture species. The trpv4 open reading frame (ORF) consists of 2616 nucleotides and encodes an 872-amino acid protein. It shares up to 94.01 % phylogenetic similarity with Thunnus maccoyii and possesses 6 transmembrane domains highly conserved with human TRPV4. Trpv4 was widely distributed across most organs and showed significant sex-biased expression. In situ hybridization data showed that trpv4 was explicitly expressed in various parts of the pituitary, from pars intermedia (PI) to rostral pars distalis (RPD) where it colocalized with prolactin 1 (prl1) in RPD. Furthermore, exposure to decreasing salinity from 35 ppt to 10 ppt demonstrated a significant upregulation of trpv4 transcription in the pituitary, gill, skin, and gonad under low-salinity conditions. Although prl1 was upregulated, follicle-stimulating hormone beta subunit (fshb) expression was decreased in the pituitaries of low-salinity groups. These findings suggest that trpv4 is regulated by salinity in chub mackerel and may play a role in reproductive responses to salinity changes. Overall, these results highlight the characterization of trpv4 in marine fish and its potential roles in osmoregulation, as well as in transmitting low-salinity signals to reproduction-related organs. The involvement of the brain–pituitary–gonad axis in this response warrants further investigation.
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Ohga H., Shibata K., Sakanoue R., Ogawa T., Kitano H., Kai S., Ohta K., Nagano N., Nagasako T., Uchida S., Sakuma T., Yamamoto T., Kim S., Tashiro K., Kuhara S., Gen K., Fujiwara A., Kazeto Y., Kobayashi T., Matsuyama M.
Scientific Reports 13 ( 1 ) 3190 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：Scientific Reports
Genome editing is a technology that can remarkably accelerate crop and animal breeding via artificial induction of desired traits with high accuracy. This study aimed to develop a chub mackerel variety with reduced aggression using an experimental system that enables efficient egg collection and genome editing. Sexual maturation and control of spawning season and time were technologically facilitated by controlling the photoperiod and water temperature of the rearing tank. In addition, appropriate low-temperature treatment conditions for delaying cleavage, shape of the glass capillary, and injection site were examined in detail in order to develop an efficient and robust microinjection system for the study. An arginine vasotocin receptor V1a2 (V1a2) knockout (KO) strain of chub mackerel was developed in order to reduce the frequency of cannibalistic behavior at the fry stage. Video data analysis using bioimage informatics quantified the frequency of aggressive behavior, indicating a significant 46% reduction (P = 0.0229) in the frequency of cannibalistic behavior than in wild type. Furthermore, in the V1a2 KO strain, the frequency of collisions with the wall and oxygen consumption also decreased. Overall, the manageable and calm phenotype reported here can potentially contribute to the development of a stable and sustainable marine product.
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Reproductive farming technology in Japanese eel and chub mackerel 査読あり
Miyanishi H., Nagano N.
Aquaculture and Fisheries 7 ( 5 ) 595 - 600 2022年9月
担当区分：最終著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Aquaculture and Fisheries
Japanese eel (Anguilla japonica) and chub mackerel (Scomber japonicus) are commercially valuable species in Asian aquaculture. The reduction in eel and chub mackerel resources has been a serious problem in recent years that should be addressed by reducing the catch of their natural populations to halt their decline and reach the Sustainable Development Goals. Furthermore, securing sufficient food supply by aquaculture is an important step in addressing the increasing demand for fish products in recent years. Traditionally, juveniles of the Japanese eel and chub mackerel have been captured to be raised in aquaculture. Owing to the extensive research on these species, new technologies have been developed for full-lifecycle aquaculture of Japanese eel in 2011 and chub mackerel in 2014. These technologies are expected to stop the decline of natural resources and provide a stable food supply. Recently, seed production of these species has increased owing to the development of successful broodstock management and larval rearing techniques. Fundamental information on oocyte maturation and ovulation and its application for artificial induction of sexual maturation is needed to produce good quality seeds of the Japanese eel and chub mackerel. Here, hormonal mechanisms and previously and newly developed methods for artificial seed production have been described.
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Barnuevo K.D., Galotta M., Mohapatra S., Sato O., Katoh H., Itoh T., Nagano N., Matsuyama M., Chakraborty T., Ohta K.
Aquaculture 612 2026年1月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Aquaculture
Temperature exerts a profound influence on the reproductive physiology of ectotherms such as fish, rendering it imperative to comprehend the long-term consequences and underlying mechanisms of temperature-related reproductive modifications in the context of a warming climate. Utilizing chub mackerel (Scomber japonicus) as a model, this study examined how variations in environmental temperature impact reproductive development, gonadotropin production, and the function of thermosensory pathways. Comparative breeding data collected from 2021 to 2024 across two aquaculture facilities, exhibiting temperature differences of up to 3.5 °C, revealed that broader temperature fluctuations may accelerate initial reproductive development while potentially impairing later reproductive stages, thereby diminishing fertilization rates and hatchability. The gene sjtrpv1, a chub mackerel homolog of mammalian TRPV 1, was cloned and characterized. It revealed its high conservation and widespread tissue expression, with sex-dependent and seasonal variations in expression patterns. In situ hybridization experiments demonstrated a strong colocalization of sjtrpv1 with fshb in FSH-producing cells within the proximal pars distalis, implying its involvement in transmitting thermal signals to the reproductive axis. Seasonal analyses showed a negative correlation between sjtrpv1 expression and environmental temperature and a positive correlation with fshb levels, suggesting a role in synchronizing reproductive timing with seasonal thermal cues. These findings imply that sjtrpv1 likely mediates the influence of temperature on reproductive processes via regulation of fshb, thereby affecting reproductive timing and success in chub mackerel. Understanding these mechanisms will facilitate the optimization of thermal management strategies in sustainable aquaculture and provide valuable insights into the reproductive adaptation of wild fish populations amid increasing ocean temperatures driven by climate change.
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Diel vertical migration of chub mackerel: preliminary evidence from a biologging study 査読あり
Yasuda T., Nagano N., Kitano H.
Marine Ecology Progress Series 598 147 - 151 2018年6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：Marine Ecology Progress Series
© Inter-Research 2018. Fishes in the genus Scomber are migratory species specialised for rapid and efficient swimming, and are also of high commercial value. Despite advances in understanding the horizontal distribution and migratory behaviour of Scomber species, knowledge remains limited about their vertical movement patterns. This paper presents a proof of concept showing the potential for using biologging techniques to help understand the vertical movement patterns of a scombrid. The vertical swimming behaviour of 1 chub mackerel S. japonicus was measured at 10 s intervals for 166 consecutive days from November to April with an electronic tag. The tagged fish showed a normal pattern of diel vertical migration (DVM) that involved movement from shallow depths at night to greater depths during the day. However, this pattern of DVM broke down or reversed on a short-term basis during the overall recording period. In addition, the fish modified the depth and amplitude of DVM in response to the vertical gradient of the water temperature. Consequently, even though the tagged individual used a wide range of depths uniformly (0 to 130 m), it remained within potentially physiologically adequate ambient water temperatures in a vertically and seasonally heterogeneous thermal environment.
DOI： 10.3354/meps12636
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Kitano H., Nagano N., Sakaguchi K., Matsuyama M.
Aquaculture Research 49 ( 1 ) 352 - 358 2018年1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：Aquaculture Research
© 2017 John Wiley & Sons Ltd Chub mackerel (Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full-life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na + /K + -ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na + /K + -ATPase in the gills decreased within 10 days after the low-salinity challenge, which implies the reduction of the energy-consuming active ion secretion under the low-salinity environment. The physiological capacity for adaptation to low-salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low-salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture.
DOI： 10.1111/are.13465
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Kitano H., Nagano N., Sakaguchi K., Matsuyama M.
Molecular Reproduction and Development 84 ( 5 ) 363 - 375 2017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：Molecular Reproduction and Development
© 2017 Wiley Periodicals, Inc. Vitellogenenesis is a physiological process common in oviparous animals. The molecular profile, modifications, and utilization of vitellogenin (VTG), a precursor of yolk protein, have been characterized in various taxa to understand oogenesis within different modes of reproduction. Hormonal regulation of VTGs has been investigated in invertebrates, such as insects and crustaceans; conversely, little is known for cephalopods. In this study, we isolated two VTG genes (ue-VTG1 and ue-VTG2) from the loliginid swordtip squid, Uroteuthis edulis, via a comprehensive survey of a transcriptome database and subsequent cDNA cloning. Structural analysis of the two ue-VTGs revealed their unique features, namely the absence of two domains usually found in VTGs from other organisms: the von Willebrand factor D domain (vWD) and the domain of unknown function 1943 (DUF1943). Levels of ue-VTG1 and ue-VTG2 transcripts in the ovary, specifically in follicular cells, increased during the late-vitellogenic phase, suggesting that yolk accumulation progresses via paracrine interactions involving follicular cells and oocytes. N-terminal amino acid sequencing of biochemically purified yolk protein revealed its origins from these two VTGs, indicating that both are functional precursors of yolk protein. These results provide information that is essential to understanding the physiological pathway of yolk synthesis, accumulation, and storage in loliginid squids.
DOI： 10.1002/mrd.22786
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Ohga H., Hirata D., Matsumori K., Kitano H., Nagano N., Yamaguchi A., Matsuyama M.
Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology 203 159 - 166 2017年1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：Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology
© 2016 Elsevier Inc. Leptin directly regulates kisspeptin neurons in the hypothalamus and gonadotropin secretion from the pituitary, making it a central player in the onset of mammalian puberty. Recently, we identified two leptin genes (lepa and lepb) and a single leptin receptor (lepr) in the marine perciform fish chub mackerel; however, the expression of these genes did not correlate with the expression of important reproductive genes or ovarian stage during female puberty. Here, we expand upon these initial observations by evaluating the expression of lepa, lepb, and lepr during pubertal transition and under differential feeding conditions in the male chub mackerel. Reverse transcription-polymerase chain reaction (RT-PCR) showed that lepa was primarily expressed in the liver of pubertal and gonadal recrudescence adults, as well as in the brain of adult fish; lepb was primarily expressed in the brain of all fish tested; and lepr was widely expressed in a variety of tissues. qRT-PCR analyses revealed significant increases in the hepatic expression of lepa in accordance with testicular stage, whereas pituitary follicle-stimulating hormone (fshβ) expression increased in unison with hepatic lepa. In contrast, expression of both brain lepa and lepb dramatically decreased during pubertal transition, with brain kisspeptin 1 (kiss1) expression strongly correlating with leptin expression patterns. In pre-pubertal males, lepa, lepb, and lper gene expression in the brain, pituitary gland, and liver decreased in fish given a high feed diet, relative to the controlled feeding group. Taken together, these results indicate high sexual specificity of leptin expression, suggesting a possible role for leptin signaling in endocrine and neuroendocrine functions during spermatogenesis in the pubertal male chub mackerel.
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Degradation of distillery lees (Shochu kasu) by cellulase-producing thraustochytrids 査読あり
Taoka Y., Nagano N., Kai H., Hayashi M.
Journal of Oleo Science 66 ( 1 ) 31 - 40 2017年1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：Journal of Oleo Science
© 2017 by Japan Oil Chemists’ Society.Single cell oils produced by oleaginous microorganisms have attracted increasing interests as a petroleum alternative energy. Marine eukaryotes, thraustochytrids were heterotrophic, and can grow rapidly and accumulate large amount of lipids containing functional fatty acids, such as docosahexaenoic acid (DHA) in their cells body. In this investigation, thraustochytrids isolated from marine environment were cultured in the medium containing an industrial waste and an unused resource, distillery lees (Shochu kasu) to produce biofuel or functional fatty acids by microorganisms. Sixty-nine thraustochytrids and Schizochytrium aggregatum ATCC 28209 were screened for cellulase production, and the activities were detected using sodium carboxymethyl cellulose (CMC) as a substrate. Based on the screening test, strain TM02Bc identified to Schizochytrium sp. was selected for the Shochu kasu degradation test and compared with S. aggregatum ATCC 28209 previously known as a cellulase-producing thraustochytrid. Strains TM02Bc and ATCC 28209 were cultured in artificial seawater containing Shochu kasu for 15 days. The two strains could degrade Schochu kasu, especially that from sweet potato Shochu (Imo Shochu). Cellulase (CMCase) and protease activities were detected in culture supernatant of both strains, and the ratio of polyunsaturated fatty acids (PUFAs) significantly increased as a result of incubation of Shochu kasu with two strains. This preliminary study indicated that strain TM02Bc was a potent candidate for Shochu kasu treatment and fatty acid production.
DOI： 10.5650/jos.ess16148
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Yasuda T., Nagano N., Kitano H., Ohga H., Sakai T., Ohshimo S., Matsuyama M.
Animal Biotelemetry 3 ( 1 ) 2015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：Animal Biotelemetry
© 2015 Yasuda et al. Background: Electronic tags are increasingly used in the studies of fish, but the attachment of electronic tags may affect their behaviour and physiology. While a number of studies have shown effects of electronic tags on fish health and behaviour, few have examined the effects of thermal conditions on the consequences of electronic tagging. In the present study, we conducted two laboratory experiments under two different water temperatures (22.5 ± 1.5 and 12.7 ± 1.8 °C) to evaluate the growth and survival of commercially reared chub mackerel Scomber japonicus tagged with a dummy electronic tag. Results: The presence of the tag, but not the surgical operation itself, significantly decreased fish survival rate under warm conditions, whereas high survival rates (ca. 96 %) were observed for both tagged and untagged fish under cold conditions. No difference in growth rate was found between the tagged and untagged fish under cold conditions, but tagged fish grew more poorly than untagged fish under warm conditions. Conclusions: Our result showed that water temperature cle arly affects the impact of tagging on the health of commercially reared chub mackerel.
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Ohga H., Matsumori K., Kodama R., Kitano H., Nagano N., Yamaguchi A., Matsuyama M.
General and Comparative Endocrinology 222 88 - 98 2015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：General and Comparative Endocrinology
© 2015 Elsevier Inc. Leptin is a hormone produced by fat cells that regulates the amount of fat stored in the body and conveys nutritional status to the reproductive axis in mammals. In the present study we identified two subtypes of leptin genes (lepa and lepb) and a leptin receptor gene (lepr) from chub mackerel (Scomber japonicus) and there gene expression under different feeding conditions (control and high-feed) and pubertal development stages was analyzed using quantitative real-time PCR. The protein lengths of LepA, LepB and LepR were 161 amino acids (aa), 163 aa and 1149 aa, respectively and both leptin subtypes shared only 15% similarity in aa sequences. In pubertal females, lepa was expressed in the brain, pituitary gland, liver, adipose tissue and ovary; however, in adult (gonadal maturation after the second in the life) females, lepa was expressed only in the liver. lepb was expressed primarily in the brain of all fish tested and was expressed strongly in the adipose tissue of adults. lepr was characterized by expression in the pituitary. The high-feed group showed a high conditioning factor level; unexpectedly, hepatic lepa and brain lepr were significantly more weakly expressed compared with the control-feed group. Furthermore, the expression levels of lepa, lepb and lepr genes showed no significant differences between pre-pubertal and post-pubertal fish. On the other hand, pituitary fshβ and lhβ showed no significant differences between different feeding groups of pre-pubertal fish. In contrast, fshβ and lhβ exp ressed abundantly in the post-pubertal fish of control feed group. Based on these results, whether leptin plays an important role in the nutritional status and pubertal onset of chub mackerel remains unknown.
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Selvaraj S., Ohga H., Nyuji M., Kitano H., Nagano N., Yamaguchi A., Matsuyama M.
Aquaculture Research 46 ( 8 ) 1866 - 1877 2015年8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：Aquaculture Research
© 2013 John Wiley & Sons Ltd. In recent years, kisspeptin peptides, encoded by kiss genes have been used to manipulate reproductive processes in farmed animals, including fish. Our previous studies demonstrated that the chub mackerel brain expresses kiss1 and kiss2 and intramuscular injection of synthetic Kiss1 pentadecapeptide (Kiss1-15) but not Kiss2 dodecapeptide (Kiss2-12) accelerates spermatogenesis in prepubertal male chub mackerel (Scomber japonicus). In the present study, we evaluated their effects in prepubertal female chub mackerel. The gonadosomatic index (GSI) values of experimental fish did not show any significant changes. Condition factor (CF) values increased significantly in Kiss1-15 treated fish, in comparison with control and GnRH analogue (GnRHa) injected fish. Histologically, only perinucleolar oocytes were found in all experimental fish. However, Kiss and GnRHa treated fish showed a significant increase in the perinucleolar oocyte diameter, in comparison with the control fish. Gene expression analyses revealed decreased expression of gnrh1 in the telencephalon-preoptic region of the brain of Kiss2-12 and GnRHa injected fish, in comparison with control fish. In contrast, GnRHa injected fish exhibited higher levels of fshβ in the pituitary, with no changes in the levels of lhβ among different treatments. Levels of circulating sex steroids, testosterone, and estradiol-17β were significantly higher in Kiss1-15 injected fish, in comparison with control fish. These results indicate that synthetic kisspeptin peptides and GnRHa can induce oocyte growth in prepubertal female chub mackerel.
DOI： 10.1111/are.12342
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Selvaraj S., Ohga H., Nyuji M., Kitano H., Nagano N., Yamaguchi A., Matsuyama M.
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology 166 ( 2 ) 228 - 236 2013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：Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Kisspeptins, encoded by kiss genes, have emerged as critical regulator of reproductive function in vertebrates. Our previous studies demonstrated that the chub mackerel (Scomber japonicus) brain expresses kiss1 and kiss2 and peripheral administration of synthetic Kiss1 pentadecapeptide (Kiss1-15) but not Kiss2 dodecapeptide (Kiss2-12) induces spermiation in sexually immature adult chub mackerel. In the present study, we evaluated the potency of Kiss1-15, Kiss2-12, and GnRH analogue (GnRHa) to induce pubertal onset in prepubertal chub mackerel. Peptides were administered through subcutaneous injection for three times (bi-weekly) over 6. weeks. Interestingly, gonadosomatic index (GSI) of Kiss1-15 treated fish increased significantly in comparison to other treatments. Histologically, 66.7% of Kiss1-15 treated fish exhibited presence of spermatozoa (SPZ) in the testes with only 28.6% of GnRHa treated fish. However, Kiss2-12 treated fish showed only spermatocytes (SC) as the advanced germ cells in the testes. In contrast, only spermatogonia (SPG) were observed in the testes of control fish. Changes in the number of testicular germ cells among treatments revealed a significantly higher number of SC, spermatids and SPZ in the Kiss1-15 treated fish. Gene expression analyses revealed no significant changes in gnrh1 in the telencephalon-preoptic region of the brain, including fshβ and lhβ in the pituitary of experimental fish. However, GnRHa treated fish showed significantly higher lhβ expression. Levels of sex steroids, 11-ketotestosterone and estradiol-17β were significantly higher in Kiss1-15 treated fish. These results indicate application of Kiss1-15 peptides for accelerating pubertal onset in chub mackerel. © 2013 Elsevier Inc.
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Effect of trace elements on growth of marine eukaryotes, tharaustochytrids
Nagano N., Nagano N., Taoka Y., Honda D., Hayashi M.
Journal of Bioscience and Bioengineering 116 ( 3 ) 337 - 339 2013年9月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Bioscience and Bioengineering
We determined the effect of trace elements on the growth of thraustochytrids. The growth of the strains cultured with the trace elements was much higher than that of the strains cultured without any trace element. Iron and zinc were particularly important to obtaining the optimum growth of thraustochytrids. © 2013 The Society for Biotechnology, Japan.
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Sakaguchi K., Matsuda T., Kobayashi T., Ohara J., Hamaguchi R., Abe E., Nagano N., Hayashi M., Ueda M., Honda D., Okita Y., Taoka Y., Sugimoto S., Okino N., Ito M., Ito M.
Applied and Environmental Microbiology 78 ( 9 ) 3193 - 3202 2012年5月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Applied and Environmental Microbiology
A versatile transformation system for thraustochytrids, a promising producer for polyunsaturated fatty acids and fatty acid-derived fuels, was established. G418, hygromycin B, blasticidin, and zeocin inhibited the growth of thraustochytrids, indicating that multiple selectable marker genes could be used in the transformation system. A neomycin resistance gene (neor), driven with an ubiquitin or an EF-1α promoter-terminator from Thraustochytrium aureum ATCC 34304, was introduced into representatives of two thraustochytrid genera, Aurantiochytrium and Thraustochytrium. The neor marker was integrated into the chromosomal DNA by random recombination and then functionally translated into neor mRNA. Additionally, we confirmed that another two genera, Parietichytrium and Schizochytrium, could be transformed by the same method. By this method, the enhanced green fluorescent protein was functionally expressed in thraustochytrids. Meanwhile, T. aureum ATCC 34304 could be transformed by two 18S ribosomal DNA-targeting vectors, designed to cause single- or double-crossover homologous recombination. Finally, the fatty acid Δ5 desaturase gene was disrupted by double-crossover homologous recombination in T. aureum ATCC 34304, resulting in an increase of dihomo-γ-linolenic acid (C20:3n-6) and eicosatetraenoic acid (C20:4n-3), substrates for Δ5 desaturase, and a decrease of arachidonic acid (C20:4n-6) and eicosapentaenoic acid (C20:5n-3), products for the enzyme. These results clearly indicate that a versatile transformation system which could be applicable to both multiple transgene expression and gene targeting was established for thraustochytrids. © 2012, American Society for Microbiology.
DOI： 10.1128/AEM.07129-11
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Nagano N., Sakaguchi K., Taoka Y., Okita Y., Honda D., Ito M., Ito M., Hayashi M.
Journal of Oleo Science 60 ( 9 ) 475 - 481 2011年8月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Oleo Science
Heterotrophic marine protists known as thraustochytrids can synthesize polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA). The biosynthetic pathways of PUFAs in thraustochytrids are poorly understood, however. In this study, we attempted to reveal the enzymes involved in DHA synthesis in thraustochytrids. Nine thraustochytrid strains representing 3 genera (Aurantiochytrium, Schizochytrium, and Thraustochytrium) were used for PCR-based detection of the genes encoding Δ5-elongase and Δ4-desaturase and for fatty acid analysis. The degenerate primers were designed to amplify the Δ5-elongase and Δ4-desaturase genes, and the partial sequences of the enzymes were obtained from the genera Thraustochytrium and Schizochytrium. These fragments were identical to those of known Δ5-elongase and Δ4-desaturase. Neither Δ5-elongase nor Δ4-desaturase was detected in the strains belonging to the genus Aurantiochytrium, however, suggesting that this group likely synthesizes DHA not via the elongation/desaturation pathway but via an alternate pathway such as the polyketide synthase pathway. The fatty acid profiles of thraustochytrids were consistent with the presence of genes involved in PUFA biosynthesis in thraustochytrid genera. Thus, our fi ndings suggest that two biosynthetic pathways for PUFAs exist in these organisms. © 2011 by Japan Oil Chemists' Society.
DOI： 10.5650/jos.60.475
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Taoka Y., Nagano N., Okita Y., Izumida H., Sugimoto S., Hayashi M.
Journal of Oleo Science 60 ( 5 ) 217 - 220 2011年5月
記述言語：英語 掲載種別：研究論文（学術雑誌）
To examine the effect of cold shock treatment on the fatty acid composition of Aurantiochytrium limacinum strain mh0186, a marine thraustochytrid, we cultivated this strain at 28°C for 72 h with shaking and stored the obtained biomass at 10°C for 72 h. A growth experiment was carried out for comparison, wherein strain mh0186 was grown at 10 and 15°C for 72 h with shaking, and it was found that the unsaturation of fatty acids was accelerated relative to that at 28°C. In the cold shock experiment, the total lipid content signifi cantly increased during storage at 10°C for 72 h. Overall, the percentage of unsaturated fatty acids such as docosahexaenoic acid was almost stable while that of n-6 docosapentaenoic acid decreased slightly, but signifi cantly, relative to that in the growth experiment. © 2011 by Japan Oil Chemists' Society.
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Taoka Y., Nagano N., Okita Y., Izumida H., Sugimoto S., Hayashi M.
Journal of Bioscience and Bioengineering 111 ( 4 ) 420 - 424 2011年4月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Bioscience and Bioengineering
Thraustochytrium aureum ATCC 34304 was grown in the presence and absence of polyoxyethylene sorbitan monooleate (Tween 80). The aim of this work was to obtain basic knowledge about the effect of Tween 80 on growth, lipid accumulation and fatty acid composition in T. aureum. The addition of Tween 80 to a culture medium significantly enhanced the growth of T. aureum, and the biomass increased with an increase of Tween 80 content. Total lipid content and total fatty acid content were significantly higher in 1.0% Tween 80 in comparison with the control (absence of Tween 80). The fatty acid profile showed that the content of C18:1n-9 (oleic acid) significantly increased as a result of the addition of Tween 80. These results indicated that part of the Tween 80 added to the medium was utilized as a carbon source or that the oleate included in Tween 80 was directly incorporated into T. aureum cells as a fatty acid. Neither the DHA content nor the percentage of DHA did not change in spite of the addition of Tween 80. However, the DHA yield significantly increased because the biomass increased due to the addition of Tween 80. © 2010 The Society for Biotechnology, Japan.
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The Distribution of Extracellular Cellulase Activity in Marine Eukaryotes, Thraustochytrids
Nagano N., Matsui S., Kuramura T., Taoka Y., Honda D., Hayashi M.
Marine Biotechnology 13 ( 2 ) 133 - 136 2011年4月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Marine Biotechnology
Cellulolytic ability was evaluated in 19 strains of thraustochytrids, representing nine genera, using carboxymethylcellulose (CMC) as a substrate. Extracellular cellulolytic enzyme activity was determined in the culture supernatants during cell growth. CMC hydrolysis was observed in 14 out of the 19 strains examined. These belonged to the genera Aplanochytrium, Botryochytrium, Oblongichytrium, Parietichytrium, Schizochytrium, Sicyoidochytrium, Thraustochytrium and Ulkenia. On the other hand, cellulolytic enzyme activity was not detected in any strains belonging to the genus Aurantiochytrium. © 2010 Springer Science+Business Media, LLC.