We report a draft sequence for the genome of the domesticated silkworm (Bombyx mori), covering 90.9% of all known silkworm genes. Our estimated gene count is 18,510, which exceeds the 13,379 genes reported for Drosophila melanogaster. Comparative analyses to fruitfly, mosquito, spider, and butterfly reveal both similarities and differences in gene content.

家蚕小卵突变体（Small egg mutant，sm），其卵体积仅及正常卵的2/3，不能受精而致死。因其卵母细胞不能正常吸收卵黄原蛋白（Vg），人们认为其原因可能是卵黄原蛋白受体基因（VgR）突变所致。本研究首先通过克隆筛选和基因组序列分析，获得了2564 bp含有pbvA的家蚕卵黄原蛋白受体基因（BmVgR）片段。将该基因片段的预测蛋白与其它物种的VgR/YPR和低密度脂蛋白受体（LDLR）家族比较，发现该基因具有LDLR家族的基本结构特征。其次，经RT-ECR检测，结果表明BmVgR在sm的不同时期的卵母细胞中都能正常转录。最后，分别对sm不同发育时期的体液和卵的总蛋白进行SDSPAGE分析，发现该突变体的卵母细胞不能正常摄取体液蛋白（包括Vg）。综合分析，sm不能正常摄取Vg，可能并不是VgR的功能异常导致，而是与滤泡细胞异常有关

We identified 277 alternative splice forms in silkworm genes based on aligning expressed sequence tags with genomic sequences, using a transcipt assembly program. A large fraction (74%) of these alternative splices are located in protein-coding regions and alter protein products, whereas only 26% are in untranslated regions. From the alternative splices located in protein-coding regions, some (43%) affect protein domains that bind various biological molecules. The vast majority of the detected alternative forms in this study appear to be novel, and potentially affect biologically meaningful control of function in silkworm genes. Our results indicate that alternative splicing in silkworm largely produces protein diversity and functional diversity, and is a widely used mechanism for regulating gene expression.

The Silkworm Knowledgebase (SilkDB) is a webbased repository for the curation, integration and study of silkworm genetic and genomic data. With the recent accomplishment of a 6X draft genome sequence of the domestic silkworm (Bombyx mori), SilkDB provides an integrated representation of the large-scale, genome-wide sequence assembly, cDNAs, clusters of expressed sequence tags (ESTs), transposable elements (TEs), mutants, single nucleotide polymorphisms (SNPs) and functional annotations of genes with assignments to InterPro domains and Gene Ontology (GO) terms. SilkDB also hosts a set of ESTs from Bombyx mandarina, a wild progenitor of B.mori, and a collection of genes from other Lepidoptera.Comparative analysis results between the domestic and wild silkworm, between B.mori and other Lepidoptera, and between B.mori and the two sequenced insects, fruitfly and mosquito, are displayed by using B.mori genome sequence as a reference framework. Designed as a basic platform, SilkDB strives to provide a comprehensive knowledgebase about the silkworm and present the silkworm genome and related information in systematic and graphical ways for the convenience of in-depth comparative studies. SilkDB is publicly accessible at http://silkworm.genomics.org.cn.

Two Bombyx mori isoforms of the gene lark, which is shown to play an important role in Drosophila circadian rhythms, were identified and named Bmlark-PA and Bmlark-PB, respectively. Bmlark-PA consists of 5 exons and encodes a protein of 343 amino acid residues which contains 3 functional domains: two RRM (RNA recognization motif) domains and an RTZF (retroviral-type zinc finger), and shares 72% identity with the Drosophila gene lark at the amino acid level. Bmlark-PB lacks the sequence between 118 and 791 nt of Bmlark-PA and codes for a protein of 68 amino acid residues, which contains no distinct functional domains. Alignments of the cDNAs of Bmlark to the genomic draft sequence of B. mori showed that the gene Bmlark had a single copy in the genome, suggesting that an alternative splicing mechanism occurs in the gene Bmlark. RT-PCR analysis indicated that Bmlark-PA was expressed only in late pupae and adult but Bmlark-PB was broadly expressed in many tissues and throughout the developmental stages from embryo to adult.

由siRNA（short interfering RNAs）介导的RNAi作为一种工具已被广泛用于基因功能研究中，并有望在不久的将来成为防治生物体疾病的强大工具。本研究通过显微注射，在家蚕中首次以siRNA介导的方式，对家蚕ABC 转运蛋白（ATP Binding Cassette Transporter）系列相关基因（Bmwh1，Bmwh2，Bmwh3）进行了siRNA干涉研究，在部分基因中得到了高效特异的干涉现象。比较分析结果初步证实siRNA正义链3’碱基错配可以增强siRNA的干涉效果。同时，实验显示了siRNA较之于dsRNA介导的RNAi具有较强的优势，表明siRNA介导的RNAi可作为基因功能分析和未来的基因操作手段在家蚕中进行应用。

The fat body plays key roles in metabolism and sustenance of growth throughout the life of a silkworm, and thus represents a model tissue for studying development and metamorphosis. Analysis of 18480 ESTs derived from larval and pupal fat body cDNA libraries allowed characterization of gene expression patterns in the fat body during metamorphosis. By Phrap assembling, 6814 estimated transcription units (TUs) were generated, 2673 of which contained 60% of the total ESTs and represented 1366 distinctive known genes. These genes were classified into 14 categories based on their known or putative functions, and most were found to be involved in metabolism and cell defense. Further comparative analysis of the expression profiles revealed that the gene expression patterns in the larval fat body strikingly differed from those in the pupal fat body. From this, we identified a subset of genes potentially associated with metamorphic events such as the formation or destruction of specific tissues, and simultaneously confirmed the stage-specific expression patterns of several identified genes using RT-PCR examination. This work will provide a valuable resource for studying regulatory mechanisms associated with fat body developmental changes and silkworm metamorphosis.

胰凝乳蛋白酶抑制剂（Chymotrypsin inhibitor,CI）是家蚕血液中主要的蛋白酶抑制因子，为其正常生长发育所不可缺少，研究a对阐明家蚕正常生理以及害虫防治等都具有重要意义。采用pH8.3、4.0聚丙烯酰胺凝胶电泳和CI活性染色法，对6个家蚕品种血液中的蛋白质含量和CI活性进行了测定，并对各品种CI活性的个体差异性进行了分析。结果表明：结合pH 8.3和pH4.O的电泳条件，可检测出Ict-D，Ict-E，Ict-A，Ict-B，Ict-H基因所支配的15种CI；6个品种中有3个具有CI个体差异性，而且Ict-E和Ict-B在有的品种或个体无活性，为非必需种类。

We made use of 81,635 expressed sequence tags (ESTs) derived from 12 different cDNA libraries of the silkworm, Bombyx mori, inbred strain Dazao (P50), to identify high-quality candidate single nucleotide polymorphisms (SNPs). By PHRAP assembling, 12,980 contigs containing 11,537 contigs assembled by more than one read were obtained, and 101 candidate SNPs and 27 single base insertions/deletions were identified from 117 contigs assembled from 1576 high-quality reads base-called with PHRED and screened on the basis of the neighborhood quality standard (NQS). Simultaneously, we also predicted 40 SNPs in coding regions (cSNPs), of which 26 were predicted to lead to amino acid non-synonymous variations and 14 synonymous substitutions. Also, the 1.66:1 ratio of transition/transversion is different from that of other insects. As the first SNP analysis of a Lepidoptera, B. mori, the single nucleotide polymorphic density is estimated to be 1:3 103 by sequence diversity. This analysis shows that expressed sequences from multiple libraries may provide an abundant source of comparative reads to mine for cSNPs from the silkworm genome.

为了研究家蚕Bombyx mori卵中储存的母性遗传信息，以未受精的肾脏型和正常型蚕卵为材料构建了cDNA文库，并对其随机测序，共获得391条表达序列标签（EST）序列，经拼接后得到374条非重复序列。生物信息学分析发现，172个非重复序列与国际数据库GenBank和silkbase中的已知基因具有较高的相似性。除3个已知母性基因外，其余主要与DNA复制、能量代谢、信号转导、转录、蛋白质结构以及胚胎发育中个体形成等相关：该结果可为进一步研究家蚕胚胎早期发育的调控提供基础数据。