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We established a genetic linkage map employing 518 simple sequence repeat (SSR, or microsatellite) markers for Bombyx mori (silkworm), the economically and culturally important lepidopteran insect as part of an international genomics program. A survey of six representative silkworm strains using 2,500 (CA)n- and (CT)n-based SSR markers revealed 17-24% polymorphism, indicating a high degree of homozygosity resulting from a long history of inbreeding. Twenty-nine SSR linkage groups were established in well characterized Dazao and C108 strains based on genotyping of 189 backcross progeny derived from an Female mated with a C108 female. The clustering was further focused to 28 groups by genotyping 22 backcross progeny derived from an F1 female mated with a C108 male. This set of SSR linkage groups was further assigned to the 28 chromosomes (established linkage groups) of silkworm aided by visible mutations and cleaved amplified polymorphic sequence markers developed from previously mapped genes, cDNA sequences, and cloned random amplified polymorphic DNAs. By integrating a visible mutation p (plain, larval marking) and 29 well conserved genes of insects onto this SSR- based linkage map, a second generation consensus silkworm genetic map with a range of 7-40 markers per linkage group and a total map length of ≈3431.9 cM was constructed and its high efficiency for genotyping and potential application for synteny studies of Lepidoptera and other insects was demonstrated. [ABSTRACT FROM AUTHOR]

A bacterial artificial chromosome (BAC) contig was constructed by chromosome walking, starting from the Hox genes of the silkworm,Bombyx mori.Bombyxorthologues of thelabial(lab) andzerknült(zen) genes were newly identified. The size of the BAC contig containing the Hox gene cluster-except thelaband Hox 2 genes-was estimated to be more than 2 Mb. TheBombyxHox cluster was mapped to linkage group (LG) 6. Thelabgene was mapped on the same LG, but far apart from the cluster. Fluorescence in situ hybridization analysis confirmed that the major Hox gene cluster andlabwere at different locations on the same chromosome inB. mori. [ABSTRACT FROM AUTHOR]

The polyubiquitin gene, encoding tandemly repeated multiple ubiquitins, constitutes a uniquitin gene subfamily. It has been demonstrated that polyubiquitin genes are subject to concerted evolution; namely, the individual ubiquitin coding units contained within a polyubiquitin gene are more similar to one another than they are to the ubiquitin coding units in the orthologous gene from other species. However there has been no comprehensive study on the concerted evolution of polyubiquitin genes in a wide range of species, because the relationships (orthologous or paralogous) among multiple polyubiquitin genes from different species have not been extensively analyzed yet. In this report, we present the results of analyzing the nucleotide sequence of polyubiquitin genes of mammals, available in the DDBJ/EMBL/GenBank nucleotide sequence databases, in which we found that there are two groups of polyubiquitin genes in an orthologous relationship. Based on this result, we analyzed the concerted evolution of the polyubiquitin gene in various species and compared the frequency of concerted evolutionary events interspecifically by taking into consideration that the rate of synonymous substitution at the polyubiquitin gene locus may vary depending on species. We found that the concerted evolutionary events in polyubiquitin genes have been more frequent in rats and Chinese hamsters than those in humans, cows, and sheep. The guinea pig polyubiquitin gene was an intermediate example. The frequency of concerted evolution in the mouse gene was unexpectedly low compared to that of other rodent genes. [ABSTRACT FROM AUTHOR]

The article discusses the Bacillus thuringiensis (Bt) toxin resistance in silkworm, Bombyx mori by the single amino acid mutation in an Adenosine-5'-triphosphate (ATP) binding cassette transporter gene. The resistance is said to involve proteins with active functions in the gut and amino acid insertion and deletion can be used to distinguish resistant from susceptible strains of silkworm. It also informs that Bt resistance is a recessive trait that requires two nonfunctioning gene copies.

Compares the linkage relationships of orthologous gene pairs in medaka, zebrafish and human. Mapping of Hox gene clusters; Extra whole-genome duplications; Divergence time estimates; Distribution of genetic markers in each medaka linkage group; Chromosome number in the last common ancestor of ray-finned and lobbed-finned fish; Gene sequences; Differential gene silencing in duplicated chromosomes.

Insect cuticle is considered an adaptable and versatile building material with roles in the construction and function of exoskeleton. Its physical properties are varied, as the biological requirements differ among diverse structures and change during the life cycle of the insect. Although the bulk of cuticle consists basically of cuticular proteins (CPs) associated with chitin, the degree of cuticular sclerotization is an important factor in determining its physical properties. Spodoptera litura , the tobacco cutworm , is an important agricultural pest in Asia. Compared to the domestic silkworm, Bombyx mori , another lepidopteran whose CP genes have been well annotated, S. litura has a shorter life cycle, hides in soil during daytime beginning in the 5th instar and is exposed to soil in the pupal stage without the protection of a cocoon. In order to understand how the CP genes may have been adapted to support the characteristic life style of S. litura , we searched its genome and found 287 putative cuticular proteins that can be classified into 9 CP families (CPR with three groups (RR-1, RR-2, RR-3), CPAP1, CPAP3, CPF, CPFL, CPT, CPG, CPCFC and CPLCA), and a collection of unclassified CPs named CPH. There were also 112 cuticular proteins enriched in Histidine residues with content varying from 6% to 30%, comprising many more His-rich cuticular proteins than B. mori. A phylogenetic analysis between S. litura, M. sexta and B. mori uncovered large expansions of RR-1 and RR-2 CPs, forming large gene clusters in different regions of S. litura chromosome 9. We used RNA-seq analysis to document the expression profiles of CPs in different developmental stages and tissues of S. litura. The comparative genomic analysis of CPs between S. litura and B. mori integrated with the unique behavior and life cycle of the two species offers new insights into their contrasting ecological adaptations. Image 1 • In total, 287 cuticular protein genes are annotated in Spodoptera litura genome. • Most RR-1 and His-rich RR-2 CPs form a major cluster in S. litura chromosome 9. • Histidine-rich RR-2 CPs are greatly expanded in S. litura compared to Bombyx mori. • RR-1 CP genes are mostly conserved among S. litura , B. mori , and Manduca sexta. • His-rich RR-2 CP genes form species-specific clades in phylogenetic analysis. [ABSTRACT FROM AUTHOR]

The Bombyx mori nucleopolyhedrovirus (BmNPV) encodes a gene homologous to the mammalian fibroblast growth factor (FGF) family. We report the cloning of B. mori and Spodoptera frugiperda orthologous genes (Bmbtl and Sfbtl, respectively) of Drosophila melanogaster breathless (btl) encoding a receptor for Branchless/FGF and show that these genes encode the receptor for a baculovirus-encoded FGF (vFGF). Sequence analysis showed that BmBtl is composed of 856 amino acid residues, which potentially encodes a 97.3-kDa polypeptide and shares structural features and sequence similarities with the FGF receptor family. Reverse transcription-PCR experiments showed that Bmbtl was abundantly expressed in the trachea and midgut in B. mori larvae, with moderate expression observed in the hemocytes and the B. mori cultured cell line BmN. We generated Sf-9 cells that stably expressed His-tagged BmBtl. Western blot analysis revealed that BmBtl was an ∼110-kDa protein. Immunoprecipitation experiments showed that BmNPV vFGF markedly phosphorylated BmBtl in Sf-9 cells. In addition, we found that BmBtl overexpression enhanced the migration activity for BmNPV vFGF. Furthermore, we generated Sf-9 cells in which Sfbtl was knocked down by transfection with double-strand RNA-expressing plasmids. In these cells, cell motility triggered by vFGF was markedly reduced. These results strongly suggest that the Btl orthologs, BmBtl and SfBtl, are the receptors for vFGF, which mediate vFGF-induced host cell chemotaxis. [ABSTRACT FROM AUTHOR]

Abstract: Two acetylcholinesterases (AChE, EC 3.1.1.7) cDNAs were identified and cloned from silkworm, Bombyx mori. One of those, BmAChE-o cDNA, is comprised of 3197 nucleotides which encode 638 amino acids, having an amino acid sequence homology of 72% with Drosophila melanogaster Ace-orthologous AChE (AO-AChE). In some species, another AChE group based on the sequence, Drosophila Ace-paralogous AChE (AP-AChE) has been recognized in relation to organophosphate- or carbamate-resistance, but there have been few reports of AP-AChE among lepidopteran species. However, we isolated the AP-AChE from lepidopteran silkworm, and cloned full ORF as BmAChE-p, which cDNA consisted of 2465 nucleotides that encode 683 amino acids. The homologies with other AP-AChEs were over 60% when compared. Although silkworm is not a target of pesticides, the genomic information obtained in this study will contribute to insecticide-resistance study on lepidopteran pest species. [Copyright &y& Elsevier]

Abstract: The present study was conducted to clarify what occurs during the metamorphosis of the imaginal disc in insects. To understand the metamorphosis on a molecular level, the changes in expression profiles in the imaginal disc during metamorphosis were investigated. For this purpose, we constructed cDNA libraries from four different stages of wing discs of Bombyx mori, sequenced about 1000 cDNAs randomly collected from each library, and constructed a database of expressed sequence tags (EST). The morphological changes and expression profiles from EST were compared during those four stages. Microarray analysis was applied to quantify the expression of each gene in each stage in order to confirm whether the expression of the genes identified from EST was induced by 20-hydroxyecdysone (20E) in a stage-specific manner. Wing discs showed dynamic morphogenesis in 4–5 days during the preparatory stage of metamorphosis, which was under the control of an ecdysteroid. Different expressed profiles were observed in each of the four different stages by comparison of each EST clone. These profiles reflected the morphological changes of the Bombyx wing disc during metamorphosis. The results of expression profiles from the four stages suggested that the V4 stage was cell proliferating; W0, proliferating and the beginning of differentiation; W2, morphologically changing; W3, cuticle secreting. Microarray analysis showed the effectiveness of its application on 20E induction of genes in wing discs. The wing disc of B. mori is an exceptionally suitable system for understanding the relationship between morphological changes and the distribution of mRNA. [Copyright &y& Elsevier]