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Congenital infection caused by vertical transmission of microsporidia N. bombycis can result in severe economic losses in the silkworm-rearing industry. Whole-transcriptome analyses have revealed non-coding RNAs and their regulatory networks in N. bombycis infected embryos and larvae. However, transcriptomic changes in the microsporidia proliferation and host responses in congenitally infected embryos and larvae remains unclear. Here, we simultaneously compared the transcriptomes of N. bombycis and its host B. mori embryos of 5-day and larvae of 1-, 5- and 10-day during congenital infection. For the transcriptome of N. bombycis, a comparison of parasite expression patterns between congenital-infected embryos and larva showed most genes related to parasite central carbon metabolism were down-regulated in larvae during infection, whereas the majority of genes involved in parasite proliferation and growth were up-regulated. Interestingly, a large number of distinct or shared differentially expressed genes (DEGs) were revealed by the Venn diagram and heat map, many of them were connected to infection related factors such as Ricin B lectin, spore wall protein, polar tube protein, and polysaccharide deacetylase. For the transcriptome of B. mori infected with N. bombycis, beyond numerous DEGs related to DNA replication and repair, mRNA surveillance pathway, RNA transport, protein biosynthesis, and proteolysis, with the progression of infection, a large number of DEGs related to immune and infection pathways, including phagocytosis, apoptosis, TNF, Toll-like receptor, NF-kappa B, Fc epsilon RI, and some diseases, were successively identified. In contrast, most genes associated with the insulin signaling pathway, 2-oxacarboxylic acid metabolism, amino acid biosynthesis, and lipid metabolisms were up-regulated in larvae compared to those in embryos. Furthermore, dozens of distinct and three shared DEGs that were involved in the epigenetic regulations, such as polycomb, histone-lysine-specific demethylases, and histone-lysine-N-methyltransferases, were identified via the Venn diagram and heat maps. Notably, many DEGs of host and parasite associated with lipid-related metabolisms were verified by RT-qPCR. Taken together, simultaneous transcriptomic analyses of both host and parasite genes lead to a better understanding of changes in the microsporidia proliferation and host responses in embryos and larvae in N. bombycis congenital infection., (© 2024. The Author(s).)

Importance: There are a few reports on the resistance of microsporidia, including Nosema bombycis . Here, the alkali-soluble germination proteins of N. bombycis were used as immunogens to prepare a monoclonal antibody, and its single-chain variable fragments effectively blocked microsporidia infection. Our study has provided novel strategies for microsporidiosis control and demonstrated a useful method for the potential treatment of other microsporidia diseases., Competing Interests: The authors declare no conflict of interest.

Microsporidia are a group of obligate intracellular parasites that infect almost all animals, causing serious human diseases and major economic losses to the farming industry. Nosema bombycis is a typical microsporidium that infects multiple lepidopteran insects via fecal-oral and transovarial transmission (TOT); however, the underlying TOT processes and mechanisms remain unknown. Here, we characterized the TOT process and identified key factors enabling N. bombycis to invade the ovariole and oocyte of silkworm Bombyx mori. We found that the parasites commenced with TOT at the early pupal stage when ovarioles penetrated the ovary wall and were exposed to the hemolymph. Subsequently, the parasites in hemolymph and hemolymph cells firstly infiltrated the ovariole sheath, from where they invaded the oocyte via two routes: (I) infecting follicular cells, thereby penetrating oocytes after proliferation, and (II) infecting nurse cells, thus entering oocytes following replication. In follicle and nurse cells, the parasites restructured and built large vacuoles to deliver themselves into the oocyte. In the whole process, the parasites were coated with B. mori vitellogenin (BmVg) on their surfaces. To investigate the BmVg effects on TOT, we suppressed its expression and found a dramatic decrease of pathogen load in both ovarioles and eggs, suggesting that BmVg plays a crucial role in the TOT. Thereby, we identified the BmVg domains and parasite spore wall proteins (SWPs) mediating the interaction, and demonstrated that the von Willebrand domain (VWD) interacted with SWP12, SWP26 and SWP30, and the unknown function domain (DUF1943) bound with the SWP30. When disrupting these interactions, we found significant reductions of the pathogen load in both ovarioles and eggs, suggesting that the interplays between BmVg and SWPs were vital for the TOT. In conclusion, our study has elucidated key aspects about the microsporidian TOT and revealed the key factors for understanding the molecular mechanisms underlying this transmission., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Wang 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.)

Bombyx mori nucleopolyhedrovirus (BmNPV) poses a significant threat to sericulture production, and traditional sanitation practices remain the main strategy for controlling BmNPV infection. Although RNAi targeting BmNPV genes engineered into transgenic silkworms has shown to be a promising approach in reducing viral infection, it cannot block viral entry into host cells. Therefore, there is an urgent need to develop new effective prevention and control measures. In this study, we screened a monoclonal antibody 6C5 that potently neutralizes BmNPV infection by clamping the internal fusion loop of the BmNPVglycoprotein64 (GP64). Furthermore, we cloned the VH and VL fragments of mAb-6C5 from the hybridoma cell, and the eukaryotic expression vector of scFv6C5 was constructed to anchor the antibody on the cell membrane. The GP64 fusion loop antibody-expressing cells exhibited a reduced capacity for BmNPV infection. The results from our study provide a novel BmNPV control strategy and lay the foundation for the future development of transgenic silkworms with improved antiviral efficacy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Microsporidia are ubiquitous in the environment, infecting almost all invertebrates, vertebrates, and some protists. The microsporidian Nosema bombycis causes silkworms pébrine disease and leads to huge economic losses. Parasite secreted proteins play vital roles in pathogen-host interactions. Serine protease inhibitors (serpins), belonging to the largest and most broadly distributed protease inhibitor superfamily, are also found in Microsporidia. In this study, we characterized 19 serpins (NbSPNs) in N. bombycis ; eight of them were predicted with signal peptides. All NbSPN proteins contain a typical conserved serpin (PF00079) domain. The comparative genomic analysis revealed that microsporidia serpins were only found in the genus Nosema . In addition to N. bombycis , a total of 34 serpins were identified in another six species of Nosema including N. antheraeae (11), N. granulosis (8), Nosema sp. YNPr (3), Nosema sp. PM-1 (3), N. apis (4), and N. ceranae (5). Serpin gene duplications in tandem obviously occurred in Nosema antheranae . Notably, the NbSPNs were phylogenetically clustered with serpins from the Chordopoxvirinae , the subfamily of Poxvirus. All 19 NbSPN transcripts were detected in the infected midgut and fat body, while 19 NbSPN genes except for NbSPN12 were found in the transcriptome of the infected silkworm embryonic cell line BmE-SWU1. Our work paves the way for further study of serpin function in microsporidia.

Nosema bombycis Naegeli (Dissociodihaplophasida: Nosematidae), an obligate intracellular parasite of the silkworm Bombyx mori, causes a devastating disease called pébrine. Every year pébrine will cause huge losses to the sericulture industry worldwide. Until now, there are no effective methods to inhibit the N. bombycis infection in silkworms. In this study, we first applied both the novel protein degradation Trim-Away technology and NSlmb (F-box domain-containing in the N-terminal part of supernumerary limbs from Drosophila melanogaster) to lepidopteran Sf9-III cells to check for specific degradation of a target protein in combination with a single-chain Fv fragment (scFv). Our results showed that the Trim-Away and NSlmb systems are both amenable to Sf9-III cells. We then created transgenic cell lines that overexpressed the protein degradation system and N. bombycis chimeric scFv targeting spore wall protein NbSWP12 and evaluated the effects of the insect transgenic cell lines on the proliferation of N. bombycis. Both methods could be applied to cell lines and both Trim-Away and NSlmb ubiquitin degradation systems effectively inhibited the proliferation of N. bombycis. Further, either of these degradation systems could be applied to individual silkworms through a transgenic platform, which would yield individual silkworms with high resistance to N. bombycis, thus greatly speeding up the process of acquiring resistant strains., (© The Author(s) 2022. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Baculovirus is a powerful tool for biological control in agriculture and foreign gene expression and delivery in insect and mammalian cells. Baculovirus enters host cells by multiple endocytic pathways; however, the current understanding of the Bombyx mori nucleopolyhedrovirus (BmNPV) entry mechanism remains limited. Previous studies have identified NPC1 and NPC2 as important host factors for viral infection in insect cells, although their exact role in viral infection has not yet been determined. In this study, we demonstrate that the BmNPC1 protein is an important intracellular factor for BmNPV escape from the endosomal compartment, and the expression of BmNPC1 in Sf9 cells confers the virus the ability to enter into the nucleus of Sf9 cells. Additionally, the second luminal domain of BmNPC1 (BmNPC1-C) binds to the viral glycoprotein gp64, and preincubation of BmNPV with purified BmNPC1-C inhibits virus infection. Furthermore, knockout of the BmNPC2 protein results in reduced efficiency of viral fusion with the endosomal membrane, and BmNPC2 protein interacts directly with both viral envelope glycoprotein gp64 and the host BmNPC1 protein. BmNPC2 was found to be incorporated into progeny viral particles. Taken together, our results suggest that NPC2 protein incorporated into viral particles may facilitate viral infection through promoting the interaction of BmNPV and NPC1 in the endosome, thus enhancing viral fusion and escape from endosomes. These results, combined with those from previous studies, support that BmNPV hijacks two important cholesterol receptor members (NPC1 and NCP2) in the cholesterol intracellular transport pathway for viral entry into host cells. IMPORTANCE Baculovirus is an important biological factor for controlling insect populations and represents a powerful biological tool for gene delivery and expression. However, the host receptor of baculovirus is still unknown. In this study, we demonstrate that BmNPC1 protein is an important intracellular factor for BmNPV escape from the endosomal compartment, and the expression of BmNPC1 confers the ability of virus to enter into the host cell nucleus in nonpermissive Sf9 cells. BmNPC2 can bind to the virus and promote progeny virion infection through the NPC1-NPC2 endosome cholesterol transport pathway. We believe that our study on the BmNPV entry mechanism will further facilitate the application of baculovirus systems in eukaryotic gene delivery. Not only can the cholesterol transport pathway NPC1 protein be used by a variety of enveloped viruses, but the NPC2 protein can also be used by viruses to infect host cells. This will provide new insights into the study of enveloped virus infection mechanisms.

Nosema bombycis is a destructive and specific intracellular parasite of silkworm, which is extremely harmful to the silkworm industry. N. bombycis is considered as a quarantine pathogen of sericulture because of its long incubation period and horizontal and vertical transmission. Herein, two single-chain antibodies targeting N. bombycis hexokinase (NbHK) were cloned and expressed in fusion with the N-terminal of Slmb (a Drosophila melanogaster FBP), which contains the F-box domain. Western blotting demonstrated that Sf9-III cells expressed NSlmb-scFv-7A and NSlmb-scFv-6H, which recognized native NbHK. Subsequently, the NbHK was degraded by host ubiquitination system. When challenged with N. bombycis , the transfected Sf9-III cells exhibited better resistance relative to the controls, demonstrating that NbHK is a prospective target for parasite controls and this approach represents a potential solution for constructing N. bombycis -resistant Bombyx mori .

Silkworm Bombyx mori is an economically important insect and a lepidopteran model. Organelle proteome is vital to understanding gene functions; however, it remains to be identified in silkworm. Here, using the engineered ascorbate peroxidase APEX, we constructed transgenic B. mori embryo cells (BmE) expressing APEX-NLS, COX4-APEX, APEX-Rev, and APEX-KDEL in nucleus, mitochondrial matrix (MM), cytosol, and endoplasmic reticulum (ER), and isolated the biotin-labeled proteins using streptavidin-affinity purification, respectively. The isolated proteins were determined using LC-MS/MS and annotated by searching B. mori genomes downloaded from GenBank, SilkBase, SilkDB 2.0, and SilkDB 3.0, resulting in 842, 495, 311, and 445 organelle proteins identified, respectively. We mapped the 296 MM proteins annotated in the GenBank data to mitochondrial protein databases of the fly, human, and mouse, and found that 140 (47%) proteins are homologous to 80 fly proteins, and 65 (22%) proteins match to 31 and 29 human and mouse proteins, respectively. Protein orthology was predicted in multiple insects using OrthoMCL, producing 460 families containing 839 proteins we identified. Out of 460 families, 363 were highly conserved and found in all insects, leaving only three proteins without orthology in other insects, indicating that the identified proteins are highly conserved and probably play important roles in insects. A gene ontology enrichment analysis by clusterProfiler revealed that the nucleus proteins significantly enriched in cellular component terms of nucleus and nucleolus, the MM proteins markedly enriched in molecular function terms of nucleotide binding, and the cytosol proteins mainly enriched in biological process terms of small molecule metabolism. To facilitate the usage and analysis of our data, we developed an open-access database, Silkworm Organelle Proteome Database (SilkOrganPDB), which provides multiple modules for searching, browsing, downloading, and analyzing these proteins, including BLAST, HMMER, Organelle Proteins, Protein Locations, Sequences, Gene Ontology, Homologs, and Phylogeny. In summary, our work revealed the protein composition of silkworm BmE organelles and provided a database resource helpful for understanding the functions and evolution of these proteins.

Background: Nosema bombycis is a unicellular eukaryotic pathogen of the silkworm, Bombyx mori, and is an economic and occupational hazard in the silkworm industry. Because of its long incubation period and horizontal and vertical transmission, it is subject to quarantine measures in sericulture production. The microsporidian life-cycle includes a dormant extracellular phase and intracellular proliferation phase, with the proliferation period being the most active period. This latter period lacks spore wall protection and may be the most susceptible stage for control., Methods: In order to find suitable target for the selective breeding of N. bombycis-resistant silkworm strains, we screen highly expressed membrane proteins from the transcriptome data of N. bombycis. The subcellular localization of the candidate protein was verified by Indirect immunofluorescence analysis (IFA) and immunoelectron microscopy (IEM), and its role in N. bombycis proliferation was verified by RNAi., Results: The N. bombycis protein (NBO_76g0014) was identified as a transmembrane protein and named NbTMP1. It is homologous with hypothetical proteins NGRA_1734 from Nosema granulosis. NbTMP1 has a transmembrane region of 23 amino acids at the N-terminus. Indirect immunofluorescence analysis (IFA) results suggest that NbTMP1 is secreted on the plasma membrane as the spores develop. Western blot and qRT-PCR analysis showed that NbTMP1 was expressed in all developmental stages of N. bombycis in infected cells and in the silkworm midgut. Downregulation of NbTMP1 expression resulted in significant inhibition of N. bombycis proliferation., Conclusions: We confirmed that NbTMP1 is a membrane protein of N. bombycis. Reduction of the transcription level of NbTMP1 significantly inhibited N. bombycis proliferation, and this protein may be a target for the selective breeding of N. bombycis-resistant silkworm strains.

Nosema bombycis is an obligate intracellular pathogen that can be transmitted vertically from infected females to eggs, resulting in congenital infections in embryos. Here we investigated the proliferation characteristics of N. bombycis in silkworm embryos using a histopathological approach and deep RNA sequencing. We found that N. bombycis proliferated mainly around yolk granules at the early stage of the embryonic development, 1-2 days post oviposition (dpo). At 4-6 dpo, a portion of N. bombycis in different stages adjacent to the embryo were packaged into the newly formed intestinal lumen, while the remaining parasites continued to proliferate around yolk granules. In the newly hatched larvae (9 dpo), the newly formed spores accumulated in the gut lumen and immediately were released into the environment via the faeces. Transcriptional profiling of N. bombycis further confirmed multiplication of N. bombycis throughout every stage of embryonic development. Additionally, the increased transcriptional level of spore wall proteins and polar tube proteins from 4 dpo indicated an active formation of mature spores. Taken together, our results have provided a characterization of the proliferation of this intracellular microsporidian pathogen in congenitally infected embryos leading to vertical transmission., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Nosema bombycis, the pathogen of silkworm pébrine, causes enormous economic losses to sericulture. As such, quarantine of commercial silkworm eggs represents an important safeguard to the silkworm industry. Here, we established a user-friendly detection system based on a nucleic acid lateral flow strip (NAFLS) that combines polymerase chain reaction (PCR) and a colloidal gold strip. PCR primers were designed based on the sequence of LSU rDNA of N. bombycis and has favourable specificity for common microsporidian isolates in silkworms. The forward and reverse primers were labeled on the 5' end with biotin and carboxyfluorescein (FAM), respectively. Genomic DNA was extracted from egg samples and was used as a template for PCR, followed by subsequent detection by NALFS. The detection limit of purified N. bombycis genomic DNA was 1 pg, 100× more sensitive than that of agarose gel electrophoresis (AGE). Furthermore, the sensitivity of detection of simulated "infected" silkworm eggs was 10-100× higher than that of AGE. NALFS detected infection in 27 of 29 samples of silkworm eggs oviposited by female moths infected in lab; ≥2% infected eggs per batch are detected as positive, while ≥40% infected eggs per batch are required for detection by AGE. Collectively, NALFS is easy to use and has great potential for widespread use in the detection of N. bombycis in silkworm egg production., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Nosema bombycis is a destructive, obligate intracellular parasite of the Bombyx mori. In this study, a single-chain variable fragment (scFv) dependent technology is developed for the purpose of inhibiting parasite proliferation in insect cells. The scFv-G4, which we prepared from a mouse G4 monoclonal antibody, can target the N. bombycis spore wall protein 12 (NbSWP12). Indirect immunofluorescence assays showed that NbSWP12 located mainly on the outside of the N. bombycis cytoskeleton, although some of it co-localized with β-tubulin in the meront-stage of parasites. When meront division began, NbSWP12 became concentrated at both ends of each meront. Western blotting showed that scFv-G4 could express in Sf9-III cells and recognized native NbSWP12. The transgenic Sf9-III cell line showed better resistance than the controls when challenged with N. bombycis, indicating that NbSWP12 is a promising target in this parasite and this scFv dependent strategy could be a solution for construction of N. bombycis-resistant Bombyx mori.

Nosema bombycis is an obligate intracellular parasite, which can cause pébrine disease. To investigate the effects of N. bombycis infection, 5th-instar silkworms were challenged with N. bombycis isolate CQ1, and two-dimensional gel electrophoresis analysis was performed to analyze the differentially expressed proteins in infected and uninfected silkworm fat bodies 1, 2, 4, 6 and 8days post-infection (dpi). 46 differentially expressed proteins were identified at the 5 time points using MALDI-TOF/TOF MS. The changed proteins mainly involved in immune response, energy metabolism, and molecular synthesis. Overall, the identified proteins may provide important insights into the mechanisms of the silkworm response to N. bombycis infection., (Copyright © 2017. Published by Elsevier Inc.)

Microsporidia are obligate intracellular parasites with rigid spore walls that protect against various environmental pressures. Despite an extensive description of the spore wall, little is known regarding the mechanism by which it is deposited or the role it plays in cell adhesion and infection. In this study, we report the identification and characterization of two novel spore wall proteins, SWP7 and SWP9, in the microsporidian species Nosema bombycis. SWP7 and SWP9 are mainly localized to the exospore and endospore of mature spores and the cytoplasm of sporonts, respectively. In addition, a portion of SWP9 is targeted to the spore wall of sporoblasts earlier than SWP7 is. Both SWP7 and SWP9 are specifically colocalized to the spore wall in mature spores. Furthermore, immunoprecipitation, far-Western blotting, unreduced SDS-PAGE, and yeast two-hybrid data demonstrated that SWP7 interacted with SWP9. The chitin binding assay showed that, within the total spore protein, SWP9 and SWP7 can bind to the deproteinated chitin spore coats (DCSCs) of N. bombycis. However, binding of the recombinant protein rSWP7-His to the DCSCs is dependent on the combination of rSWP9-glutathione S-transferase (GST) with the DCSCs. Finally, rSWP9-GST, anti-SWP9, and anti-SWP7 antibodies decreased spore adhesion and infection of the host cell. In conclusion, SWP7 and SWP9 may have important structural capacities and play significant roles in modulating host cell adherence and infection in vitro. A possible major function of SWP9 is as a scaffolding protein that supports other proteins (such as SWP7) that form the integrated spore wall of N. bombycis., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Microsporidia have attracted much attention because they infect a variety of species ranging from protists to mammals, including immunocompromised patients with AIDS or cancer. Aside from the study on Nosema ceranae, few works have focused on elucidating the mechanism in host response to microsporidia infection. Nosema bombycis is a pathogen of silkworm pébrine that causes great economic losses to the silkworm industry. Detailed understanding of the host (Bombyx mori) response to infection by N. bombycis is helpful for prevention of this disease. A genome-wide survey of the gene expression profile at 2, 4, 6 and 8 days post-infection by N. bombycis was performed and results showed that 64, 244, 1,328, 1,887 genes were induced, respectively. Up to 124 genes, which are involved in basal metabolism pathways, were modulated. Notably, B. mori genes that play a role in juvenile hormone synthesis and metabolism pathways were induced, suggesting that the host may accumulate JH as a response to infection. Interestingly, N. bombycis can inhibit the silkworm serine protease cascade melanization pathway in hemolymph, which may be due to the secretion of serpins in the microsporidia. N. bombycis also induced up-regulation of several cellular immune factors, in which CTL11 has been suggested to be involved in both spore recognition and immune signal transduction. Microarray and real-time PCR analysis indicated the activation of silkworm Toll and JAK/STAT pathways. The notable up-regulation of antimicrobial peptides, including gloverins, lebocins and moricins, strongly indicated that antimicrobial peptide defense mechanisms were triggered to resist the invasive microsporidia. An analysis of N. bombycis-specific response factors suggested their important roles in anti-microsporidia defense. Overall, this study primarily provides insight into the potential molecular mechanisms for the host-parasite interaction between B. mori and N. bombycis and may provide a foundation for further work on host-parasite interaction between insects and microsporidia.

Background: Microsporidian Nosema bombycis has received much attention because the pébrine disease of domesticated silkworms results in great economic losses in the silkworm industry. So far, no effective treatment could be found for pébrine. Compared to other known Nosema parasites, N. bombycis can unusually parasitize a broad range of hosts. To gain some insights into the underlying genetic mechanism of pathological ability and host range expansion in this parasite, a comparative genomic approach is conducted. The genome of two Nosema parasites, N. bombycis and N. antheraeae (an obligatory parasite to undomesticated silkworms Antheraea pernyi), were sequenced and compared with their distantly related species, N. ceranae (an obligatory parasite to honey bees)., Results: Our comparative genomics analysis show that the N. bombycis genome has greatly expanded due to the following three molecular mechanisms: 1) the proliferation of host-derived transposable elements, 2) the acquisition of many horizontally transferred genes from bacteria, and 3) the production of abundnant gene duplications. To our knowledge, duplicated genes derived not only from small-scale events (e.g., tandem duplications) but also from large-scale events (e.g., segmental duplications) have never been seen so abundant in any reported microsporidia genomes. Our relative dating analysis further indicated that these duplication events have arisen recently over very short evolutionary time. Furthermore, several duplicated genes involving in the cytotoxic metabolic pathway were found to undergo positive selection, suggestive of the role of duplicated genes on the adaptive evolution of pathogenic ability., Conclusions: Genome expansion is rarely considered as the evolutionary outcome acting on those highly reduced and compact parasitic microsporidian genomes. This study, for the first time, demonstrates that the parasitic genomes can expand, instead of shrink, through several common molecular mechanisms such as gene duplication, horizontal gene transfer, and transposable element expansion. We also showed that the duplicated genes can serve as raw materials for evolutionary innovations possibly contributing to the increase of pathologenic ability. Based on our research, we propose that duplicated genes of N. bombycis should be treated as primary targets for treatment designs against pébrine. The genome data and annotation information of N. bombycis and N.antheraeae were submitted to GenBank (Accession numbers ACJZ01000001 -ACJZ01003558).

A single-base pair resolution silkworm genetic variation map was constructed from 40 domesticated and wild silkworms, each sequenced to approximately threefold coverage, representing 99.88% of the genome. We identified ~16 million single-nucleotide polymorphisms, many indels, and structural variations. We find that the domesticated silkworms are clearly genetically differentiated from the wild ones, but they have maintained large levels of genetic variability, suggesting a short domestication event involving a large number of individuals. We also identified signals of selection at 354 candidate genes that may have been important during domestication, some of which have enriched expression in the silk gland, midgut, and testis. These data add to our understanding of the domestication processes and may have applications in devising pest control strategies and advancing the use of silkworms as efficient bioreactors.

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.