Published Papers - Ken Sahara
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Isolation of the Thosea asigna virus (TaV) from the epizootic Setothosea asigna larvae collected in South Sumatra and a study on its pathogenicity to Limacodidae larvae in Japan.（訳）南スマトラのSetothosea asigna集団感染個体からのThosea asigna virus (TaV) 分離と日本におけるイラガ科幼虫への感染性研究
Sugiharti M, Ono C, Ito T, Asano S, Sahara K, Yulia Pujiastuti Y, Bando H
Journal of Insect Biotechnology and Sericology 79 ( 3 ) 117 - 124 2010.11 [Refereed]
International Conference Proceedings Multiple authorship
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Silk threads function as an “adhesive cleaner” for nest space in a social spider mite.（訳）社会性ハダニは絹糸を粘着クリーナーとして巣内を掃除する
Kanazawa M, Sahara K, Saito Y
Proceedings of the Royal Society B 278 ( 1712 ) 1653 - 1660 2010.11 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Individuals of the social spider mite Stigmaeopsis longus live communally in narrow, humid nests made from silk threads and display nest sanitation behaviour through the coordinated deposition of faeces. We used artificial dust to experimentally determine that females of this species use silk threads to perform regular cleaning of the nest space and eggs. We first learned that silk-weaving behaviour is not a by-product of nest building (nest reinforcement); rather, it is actively performed as a function of cleaning the living space and eggs. Furthermore, we determined the effectiveness of the attending females by artificially manipulating their natural habitat, which is clearly connected to the cleaning behaviour by parental females. As such, we have uncovered an extraordinary new role of silk threads as devices
for cleaning the nest space and/or eggs. -
Step-by-step evolution of neo-sex chromosomes in geographical populations of wild silkmoths, Samia cynthia ssp.（シンジュサンの地域個体群に見られるネオ性染色体の順次進化）
Yoshido A, Sahara K, Marec F, Matsuda Y
Heredity 106 ( 4 ) 614 - 624 2010.07 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Geographical subspecies of wild silkmoths, Samia cynthia
ssp. (Lepidoptera: Saturniidae), differ considerably in sex
chromosome constitution owing to sex chromosome fusions
with autosomes, which leads to variation in chromosome
numbers. We cloned S. cynthia orthologues of 16 Bombyx
mori genes and mapped them to chromosome spreads of
S. cynthia subspecies by fluorescence in situ hybridization
(FISH) to determine the origin of S. cynthia neo-sex
chromosomes. FISH mapping revealed that the Z chromosome
and chromosome 12 of B. mori correspond to the
Z chromosome and an autosome (A1) of S. c. ricini (Vietnam
population, 2n¼27, Z0 in female moths), respectively.
B. mori chromosome 11 corresponds partly to another
autosome (A2) and partly to a chromosome carrying
nucleolar organizer region (NOR) of this subspecies. The
NOR chromosome of S. c. ricini is also partly homologous to
B. mori chromosome 24. -
Intramolecular proteolytic nicking and binding of Bacillus thuringiensis Cry8Da toxin in BBMVs of Japanese beetle.（訳）マメコガネ中腸刷子縁膜小胞に対するBT Cry8Daトキシンのタンパク質分解性損傷と結合
Yamaguchi T, Sahara K, Bando H, Asano SI
Journal of Invertebrate Pathology 105 ( 3 ) 243 - 247 2010.07 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Yamaguchi T, Sahara K, Bando H, Asano SI (2010): Intramolecular proteolytic nicking and binding of Bacillus thuringiensis Cry8Da toxin in BBMVs of Japanese beetle. J Invertebr Pathol. 105 (3), 243-247.
[Epub ahead of print] 2010 Jul 23 -
An HDAC inhibitor increases AcMNPV gene expression in mammalian cells. （訳）哺乳動物細胞ではＡｃＭＮＰＶ遺伝子発現がHDACを抑制する
Fujita R, Ohtsuka D, Sahara K, Asano S, Bando H
Archives of Virology 155 ( 4 ) 577 - 581 2010.02 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is used as a safer viral vector in mammalian cells with potential applications in gene therapy. However, the mechanism for the insusceptibility of mammalian cells to proliferative infection by entomopathogenic viruses is not well understood. Here, we studied the significance of epigenetic modifications such as histone acetylation, histone methylation and HP1 accumulation for AcMNPV gene expression in mammalian BHK cells. Real-time PCR and chromatin immunoprecipitation with sodium butyrate revealed an important relationship between viral gene expression and histone acetylation, with implications for a mechanism of suppression of AcMNPV gene expression in BHK cells.
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Evolutionary dynamics of rDNA clusters on chromosomes of moths and butterflies (Lepidoptera).（訳）ガとチョウ類の染色体におけるrDNAクラスターのダイナミックな変化
Nguyen P, Sahara K, Yoshido A, Marec F
Genetica 138 ( 3 ) 343 - 345 2009.11 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
We examined chromosomal distribution of major ribosomal DNAs (rDNAs), clustered in the nucleolar organizer regions (NORs), in 18 species of moths and butterflies using fluorescence in situ hybridization with a codling moth (Cydia pomonella) 18S rDNA probe. Most species showed one or two rDNA clusters in their haploid karyotype but exceptions with 4–11 clusters also occurred. Our results
in a compilation with previous data revealed dynamic evolution of rDNA distribution in Lepidoptera except Noctuoidea, which showed a highly uniform rDNA pattern. In
karyotypes with one NOR, interstitial location of rDNA
prevailed, whereas two-NOR karyotypes showed mostly
terminally located rDNA clusters. A possible origin of the
single interstitial NOR by fusion between two NOR-hromosomes
with terminal rDNA clusters lacks support in available data. In some species, spreading of rDNA to new,
mostly terminal chromosome regions was found. -
Extensive conserved synteny of genes between the karyotypes of Manduca sexta and Bombyx mori revealed by BAC-FISH mapping.（訳）遺伝子マッピングにより明らかになったカイコとタバコスズメガの広範な遺伝子シンテニー
Yasukochi Y, Tanaka-Okuyama M, Shibata F, Yoshido A, Marec F, Wu C, Zhang H-B, Goldsmith MR, Sahara K
PLoS ONE 4 ( 10 ) e7465 2009.10 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
(2009): Extensive conserved synteny of genes between the karyotypes of Manduca sexta and Bombyx mori revealed by BAC-FISH mapping. PLoS ONE 4(10): e7465. doi:10.1371/journal.pone.0007465 +: the same contribution
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Takemura Y, Sahara K, Mochida Y, Ohnuma A
Applied Entomology and Zoology 44 ( 3 ) 413 - 417 2009.08 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Feasible methods for sperm cryopreservation and subsequent artificial insemination are urgently needed to maintain
silkworm genetic resources with less laborious work and space cost. We have discovered that loss of the fertilizing
ability of cryopreserved diploid (p50) semen was restored by the addition of either fresh or frozen apyrene sperm
from triploid donors. To decrease usage of the amount of stored diploid semen, we monitored the effective ratio of
cryopreserved p50 semen and apyrene sperm from triploid males to restore fecundity. Restoration of the fertilizing
ability of cryopreserved p50 semen was kept by roughly one fourth decrease of the amount by increasing the apyrene
sperm ratio. Because semen collection from diploid males requires skillful and careful techniques, decreasing the
amount of cryopreserved semen may practically save laborious work. -
Molecular phylogeny of Stigmaeopsis, with special reference to speciation through host plant Shift.（訳）宿主植物のシフトを考慮したスゴモリはダニ属の分子系統
Sakagami T, Saito Y, Kongchuensin M, Sahara K
Annals of the Entomological Society of Ameria 102 ( 3 ) 360 - 366 2009.05 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Similar nest-weaving habits and sociality characterize all the species belonging to the recently reinstated spider mite genus Stigmaeopsis. Molecular phylogenetic analysis using 28S rDNA shows that Stigmaeopsis forms a distinct clade and that there is another unrecognized clade involving
Schizotetranychus species with comparable nest-weaving habits distributing in tropical regions. Furthermore,
the phylogenic hypothesis suggests that Stigmaeopsis miscanthi (Saito) inhabiting Miscanthus sinensis Anderss. shared a common ancestor with Stigmaeopsis longus (Saito) inhabiting Sasa senanensis (Franch. et Sav.), both mite species having very similar social systems. We conÞrmed
reproductive isolation between them and tested the suitability of the two plant species as hosts for these two mite species. -
Shibata F, Sahara K, Naito Y, Yasukochi Y
Zoological Science 26 ( 3 ) 187 - 190 2009.03 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Multicolor fluorescence in-situ hybridization (FISH) and subsequent reprobing of chromosome preparations increase the number of chromosomes and/or anchor loci on the chromosomes simultaneously identified. Reprobing techniques have been widely applied to chromosomes of vertebrates and plants. We have developed a novel reprobing protocol that utilizes multicolor FISH and bacterial artificial chromosome (BAC) probes to examine chromosome preparations in a model lepidopteran species, the silkworm, Bombyx mori. With standard two-color BAC-FISH, routinely used to map genes on B. mori chromosomes, we could localize only two probes on one preparation,
whereas our new protocol combining five-color BAC-FISH and preparation reprobing enabled us to simultaneously map 10 probes, as demonstrated with the Bombyx Z chromosome. The improved BAC-FISH technique will facilitate karyotyping and synteny analysis in Lepidoptera. -
Discovery of a novel Bacillus thuringiensis Cry8D protein and the unique toxicity of the Cry8D-class proteins against scarab beetles.（訳）新規Btタンパクの発見とCry8Dのコガネムシ類に対する特異な殺虫化性
Yamaguchi T, Sahara K, Bando H, Asano SI
Journal of Invetebrate Pathology 99 ( 3 ) 257 - 262 2008.06 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
A novel cry gene, cry8Db, highly toxic to scarab beetles such as the Japanese beetle, Popillia japonica Newman, was cloned from an isolate of Bacillus thuringiensis(Bt), BBT2-5. The cry8Db gene has 3525bp nucleotides and codes for a protein of 1174 amino acid residues. The protein, Cry8Db, has typical Bt characteristics such as the 8-block, conserved sequences and the three-domain 3D toxin structure as defined with Cry3Aa.The Cry8Db protein was assayed along with the other scarab active Cry8Da and Cry8Ca against the Japanese beetle. While Cry8Da and Cry8Db had toxicity against both adults and larvae of the Japanese beetle, Cry8Ca was toxic to only larvae. Cry8Ca showed no toxicity against the adult beetle up to 30 microg per 1 cm(2) of leaf discs on which the protein was applied.
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Sex chromosomes and sex determination in Lepidoptera （訳）鱗翅目昆虫における性染色体と性決定
Traut W, Sahara K, Marec F
Sexual Development 1 ( 6 ) 332 - 346 2008.01 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
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Conserved synteny of genes between chromosome 15 of Bombyx mori and a chromosome of Manduca sexta shown by five-color BAC-FISH.（訳）5色プローブBAC-FISHにより示されたカイコとタバコスズメガ第15染色体のシンテニー
Sahara K, Yoshido A, Marec F, Fuková I, Zhang H-B,Wu C, Goldsmith MR, Yasukochi Y
Genome 50 ( 11 ) 1061 - 1065 2007.11 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
The successful assignment of the existing genetic linkage groups (LGs) to individual chromosomes and the second-generation linkage map obtained by mapping a large number of bacterial artificial chromosome (BAC) contigs in the silkworm, Bombyx mori, together with public nucleotide sequence databases, offer a powerful tool for the study of synteny between karyotypes of B. mori and other Lepidopteran species. Conserved synteny of genes between particular chromosomes can be identified by comparatively mapping orthologous genes of the corresponding linkage groups with the help of BAC-FISH (fluorescent in situ hybridization). To achieve higher-throughput comparative mapping using BAC-FISH in Lepidoptera, we developed a protocol for five-color BAC-FISH, which allowed us to map simultaneously 6 different BAC probes to chromosome 15 in B. mori. All 6 M. sexta BAC clones hybridized to a single M. sexta bivalent in pachytene spermatocytes.
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Detection of gamma-tubulin in mitotic division of Bombyx mori (Lepidoptera) and Chortophaga viridifasciata (Orthoptera).（訳）カイコとバッタ類の体細胞分裂記におけるγチューブリン検出
Matsuda Y, Sahara K, Yasukochi Y, Yamashiki N
Zoological Science 24 ( 8 ) 781 - 786 2007.08 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
We detected a putative gamma-tubulin gene in silico and detected BACs containing the gene from a Bombyx mori BAC library. BAC-FISH mapping revealed that the gene is located on chromosome 5. To observe the distribution of gamma-tubulin, we employed antibodies against mammalian gamma-tubulin peptides. Western blot analysis disclosed a band very similar in size to gamma-tubulin protein in other species (approximately 48 kDa). In mitotic metaphase of B. mori spermatogonial cells, gamma-tubulin is exclusively localized in the spindle poles, where the centrosomes occur. We applied the same system to the grasshopper Chortophaga viridifasciata, as a representative of insect orders in which the gamma-tubulin distribution had not previously been studied. Gamma-tubulin was also found in the spindle poles during metaphase of spermatogonial cells in the grasshopper.
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Ecdysone response element in a baculovirus immediate-early gene, ie1, promoter.（訳）核多核体病ウイルスのie1遺伝子に認められるエクダイソン応答配列
Kojima K, Oritani K, Nakatsukasa T, Asano S, Sahara K, Bando H.
Virus Research 130 ( 43832 ) 202 - 209 2007.07 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
A computer-assisted analysis identified tentative target sequences for regulatory proteins including ecdysone-inducible factors such as BmFTZ-F1 and Broad-Complex Z4 (BR-C Z4) in the ie1 promoter of BmNPV. A transient expression experiment using BmN cells and a series of truncated ie1 promoter constructs demonstrated that the activity of the ie1 promoter responded to alpha-ecdysone and 20-hydroxyecdysone, which required a tridecameric nucleotide stretch (ie1EcRE, 5'-GTGTTATCGACCT-3') homologous to the ecdysone response element reported for Drosophila (DmEcRE). RT-PCR demonstrated the expression of BmEcR and BmUSP, which are required as ecdysone-specific activators for EcRE-mediated activation, in BmN cells. Furthermore, the ie1 EcRE-mediated response was confirmed by using a recombinant BmNPV possessing a luciferase gene under the control of the ie1 promoter with or without ie1 EcRE. This is the first report of an ecdysone response element in a baculoviral gene promoter.
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Yoshido A, Yasukochi Y, Marec F, Abe H, Sahara K
Journal of Insect Biotechnology and Sericology 76 ( 1 ) 1 - 7 2007.02 [Refereed]
Academic Journal Multiple authorship
We newly isolated seven W chromosome derived bacterial artificial chromosome (W-BAC) clones from Bombyx mori BAC libraries by means of six different STS primer sets, which amplify each different female specific DNA fragment. Two color fluorescence in situ hybridization (FISH) with 19L6H W-BAC probe as a standard W-chromosome painter disclosed that six out of seven new W-BAC probes strongly highlighted the whole W chromosome in B. mori. Besides the W, hybridization signals occurred in telomeric and/or subtelomeric regions of the autosomes. The remaining W-BAC, 20H9D, provided discontinuous signals, which appeared in both terminal and central compartments of the W chromosome. A representative of W-chromosome painting BACs, 19L6H, and 20H9D W-BAC were hybridized to chromosome spreads of Bombyx mandarina females. The 19L6H W-BAC bound to the whole B. mandarina W chromosome as in B. mori.
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Yoshido A, Yamada Y, Sahara K
Journal of Insect Biotechnology and Sericology 75 ( 3 ) 141 - 151 2006.10 [Refereed]
Academic Journal Multiple authorship
We newly identified the W chromosome in eight lepidopteran species and confirmed the absence of W chromosome in Caligula japonica females with the Z0 sex chromosome constitution by means of genomic in situ hybridization (GISH). In pachytene oocytes of species with the WZ/ZZ sex chromosome system, female-derived genomic probes of the respective species highlighted the whole W chromosome thread in the WZ bivalent and also stained specific autosomal region(s) with telomeric and/or subtelomeric signals. On the basis of GISH results obtained in this study and earlier published, we classified karyotypes of lepidopteran species into three types.
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Cloning and expression of two crystal protein genes, cry30Ba1 and cry44Aa1, obtained from a highly mosquitecidal strain, Bacillus thuringiensis subsp. entomocidus INA288.（訳）強い蚊類殺虫活性をもつBT亜種entomocidus INA288由来の2つの結晶タンパク質遺伝子のクローニングと発現
Ito T, Ikeya T, Sahara K, Bando H, Asano S
Applied and Environmental Microbiology 72 ( 8 ) 5673 - 5676 2006.08 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Two novel crystal protein genes, cry30Ba and cry44Aa, were cloned from Bacillus thuringiensis subsp. entomocidus INA288 and expressed in an acrystalliferous strain. Cry44Aa crystals were highly toxic to second-instar Culex pipiens pallens (50% mortality concentration [LC50] = 6 ng/ml) and Aedes aegypti (LC50 = 12 ng/ml); however, Cry30Ba crystals were not toxic.
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Apyrene sperm from the triploid donors restore fecundity of cryopreserved semen in Bombyx mori.（訳）無核精子は凍結保存したカイコ精液の受精能力を回復させる
Takemura Y, Sahara K, Mochida Y, Ohnuma A
Journal of Insect Physiology 52 ( 10 ) 1021 - 1026 2006.07 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
Female moths of Bombyx mori were artificially inseminated with cryopreserved semen. The fertility of inseminated females varied from 0% to 76.9% depending on the strain. Addition of fresh semen from triploid males, which are infertile but whose semen includes intact apyrene sperm, greatly improved fecundity of cryopreserved semen from normal males. Frozen apyrene sperm from the triploid donors also improved the fecundity of females, inseminated with cryopreserved normal semen, but less than fresh semen from triploid males. Fertilization success in B. mori requires the presence of both, intact eupyrene and apyrene sperm. Our results show that eupyrene sperm tolerate the cryopreservation process better than apyrene sperm. Hence, we recommend to add apyrene sperm from the triploid donors as helper sperm routinely to cryopreserved semen in artificial insemination. This may advance the application of cryopreservation as a routine technique to maintain silkworm resources.
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A second generation integrated map of the silkworm reveals synteny and conserved gene order between lepidopteran insects.（訳）第二世代のカイコ分子連関地図は鱗翅目昆虫間の遺伝子配置の保存性とシンテニーを明らかとした
Yasukochi Y, Ashakumary LA, Baba K, Yoshido A, Sahara K
Genetics 173 ( 3 ) 1319 - 1328 2006.03 [Refereed]
Bulletin of University, Institute, etc. Multiple authorship
A second-generation linkage map was constructed for the silkworm, Bombyx mori, focusing on mapping Bombyx sequences appearing in public nucleotide databases and bacterial artificial chromosome (BAC) contigs. A total of 874 BAC contigs containing 5067 clones (22% of the library) were constructed by PCR-based screening with sequence-tagged sites (STSs) derived from whole-genome shotgun (WGS) sequences. A total of 523 BAC contigs, including 342 independent genes registered in public databases and 85 expressed sequence tags (ESTs), were placed onto the linkage map. We found significant synteny and conserved gene order between B. mori and a nymphalid butterfly, Heliconius melpomene, in four linkage groups (LGs), strongly suggesting that using B. mori as a reference for comparative genomics in Lepidotera is highly feasible.