Receptor-mediated endocytosis using a β1 integrin-dependent internalization was considered as the primary mechanism for the initiation of mammalian reovirus infection. Bombyx mori cypovirus (BmCPV) is a member of Reoviridae family which mainly infects the midgut epithelium of silkworm; the cell entry of BmCPV is poorly explored. In this study, co-immunoprecipitation (Co-IP), virus overlay protein binding assay (VOPBA), and BmCPV-protein interaction on the polyvinylidene difluoride membrane (BmCPV-PI-PVDF) methods were employed to screen the interacting proteins of BmCPV, and several proteins including integrin beta and receptor for activated protein kinase C (RACK1) were identified as the candidate interacting proteins for establishing the infection of BmCPV. The infectivity of BmCPV was investigated in vivo and in vitro by RNA interference (RNAi) and antibody blocking methods, and the results showed that the infectivity of BmCPV was significantly reduced by either small interfering RNA-mediated silencing of integrin beta and RACK1 or antibody blocking of integrin beta and RACK1. The expression level of integrin beta or RACK1 is not the highest in the silkworm midgut which is a principal target tissue of BmCPV, suggesting that the molecules other than integrin beta or RACK1 might play a key role in determining the tissue tropism of BmCPV infection. The establishment of BmCPV infection depends on other factors, and these factors interacted with integrin beta and RACK1 to form receptor complex for the cell entry of BmCPV.

•The small VP7 protein was present in BmCPV.•The replication of BmCPV genome was decreased by reducing vp7 gene expression.•This novel product was generated with a leaky scanning mechanism.The genome of Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) contains 10 double stranded RNA segments (S1–S10). The segment 7 (S7) encodes 50 kDa protein which is considered as a structural protein. The expression pattern and function of p50 in the virus life cycle are still unclear. In this study, the viral structural protein 7 (VP7) polyclonal antibody was prepared with immunized mouse to explore the presence of small VP7 gene-encoded proteins in Bombyx mori cytoplasmic polyhedrosis virus. The expression pattern of vp7 gene was investigated by its overexpression in BmN cells. In addition to VP7, supplementary band was identified with western blotting technique. The virion, BmCPV infected cells and midguts were also examined using western blotting technique. 4, 2 and 5 bands were detected in the corresponding samples, respectively. The replication of BmCPV genome in the cultured cells and midgut of silkworm was decreased by reducing the expression level of vp7 gene using RNA interference. In immunoprecipitation experiments, using a polyclonal antiserum directed against the VP7, one additional shorter band in BmCPV infected midguts was detected, and then the band was analyzed with mass spectrum (MS), the MS results showed thatone candidate interacted protein (VP7 voltage-dependent anion-selective channel-like isoform, VDAC) was identified from silkworm. We concluded that the novel viral product was generated with a leaky scanning mechanism and the VDAC may be an interacted protein with VP7.

The mechanism of how Bombyx mori nucleopolyhedrovirus (BmNPV) enters cells is unknown. The primary components of membrane lipid rafts are proteins and cholesterol, and membrane lipid rafts are thought to be an active region for host–viral interactions. However, whether they contribute to the entry of BmNPV into silkworm cells remains unclear. In this study, we explored the membrane protein components of lipid rafts from BmN cells with mass spectrometry (MS). Proteins and cholesterol were investigated after establishing infection with BmNPV in BmN cells. In total, 222 proteins were identified in the lipid rafts, and Gene Ontology (GO) annotation analysis showed that more than 10% of these proteins had binding and catalytic functions. We then identified proteins that potentially interact between lipid rafts and BmNPV virions using the Virus Overlay Protein Blot Assay (VOPBA). A total of 65 proteins were analyzed with MS, and 7 were predicted to be binding proteins involved in BmNPV cellular invasion, including actin, kinesin light chain-like isoform X2, annexin B13, heat-shock protein 90, barrier-to-autointegration factor B-like and serine/arginine-rich splicing factor 1 A-like. When the cholesterol of the lipid rafts from the membrane was depleted by methyl-β-cyclodextrin (MβCD), BmNPV entry into BmN cells was blocked. However, supplying cholesterol into the medium rescued the BmNPV infection ability. These results show that membrane lipid rafts may be the active regions for the entry of BmNPV into cells, and the components of membrane lipid rafts may be candidate targets for improving the resistance of the silkworm to BmNPV.

Bombyx mori nucleopolyhedrovirus (BmNPV) is a major pathogen that specifically infects the domestic silkworm and causes serious economic loss to sericulture around the world. The function of BmNPV Bm59 gene in the viral life cycle is inconclusive. To investigate the role of Bm59 during viral infection, the transcription initiation site and temporal expression of Bm59 were analyzed, and Bm59-knockout virus was generated through homologous recombination in Escherichia coli. The results showed that Bm59 is an early transcription gene with an atypia early transcriptional start motif. Budded virion (BV) production and DNA replication in the BmN cells transfected with the Bm59-knockout virus bacmid were similar to those in the cells transfected with the wild-type virus. Electron microscopy revealed that the occlusion-derived virus can be produced in cells infected with the Bm59-knockout virus. These results indicated that Bm59 is an early gene and is not essential for viral replication or assembly of BmNPV. These findings suggested that non-essential gene (Bm59) remained in the viral genome, which may interact with other viral/host genes in a certain situation.

Bombyx mori bidensovirus (BmBDV) was previously termed as Bombyx mori densovirus type 2 and later it was reclassified in the new genus bidensovirus of the new family Bidnaviridae. The genome of BmBDV Zhenjiang isolate (BmBDV-Z) consists of two non-homologous single-stranded linear DNA molecules VD1 and VD2 which are encapsidated into separate virion. To investigate the infectivity of BmBDV DNA, recombinant plasmids pGEM-VD1 inserted with VD1 genome were transfected into the BmN cells of silkworm. Structural proteins of BmBDV were detected with Western blot and immunofluorescence assay, which indicates pGEM-VD1 replicated in the transfected BmN cells and viral proteins were also expressed. Through TEM observation, we identified about 20 nm BmBDV-like viral particles, which confirmed that BmBDV can be generated after transfection. Subsequently, a recombinant baculovirus BmBac-VD1 inserted with VD1 genome was constructed. Results of Western blot and immunofluorescence assay indicated that viral structural proteins of BmBDV were expressed in the BmBac-VD1-infected cells. Baculiform and spherical virions were also observed in infected cells by TEM, and two kinds of virions were separated. However, results of molecular biological detection revealed that infectious sequence from BmBac-VD1 was packaged within spherical virion. Therefore, we suggested that vector inserted with BmBDV genomic DNA showed infectivity, and BmBDV-like viral particles packaging recombinant DNA can be produced in the cultured BmN cells. Outcome of our current research provided not only a new method of infection to explore the gene function of BmBDV in vitro but also a protocol to facilitate development of more effective new-type pesticides.

Nosema bombycis, a microsporidium, is a pathogen of pebrine disease of silkworms, and its genomic DNA sequences had been determined. Thus far, the research of gene functions of microsporidium including N. bombycis cannot be performed with gain/loss of function. In the present study, we targeted to construct transgenic N. bombycis. Therefore, hemocytes of the infected silkworm were transfected with a non-transposon vector pIZT/V5-His vector in vivo, and the blood, in which the hemocyte with green fluorescence could be observed, was added to the cultured BmN cells. Furthermore, normal BmN cells were infected with germinated N. bombycis, and the infected cells were transfected with pIZT/V5-His. Continuous fluorescence observations exposed that there were N. bombycis with green fluorescence in some N. bombycis-infected cells, and the extracted genome from the purified N. bombycis spore was used as templates. PCR amplification was carried out with a pair of primers for specifically amplifying the green fluorescence protein (GFP) gene; a specific product representing the gfp gene could be amplified. Expression of the GFP protein through Western blotting also demonstrated that the gfp gene was perfectly inserted into the genome of N. bombysis. These results illustrated that exogenous gene can be integrated into N. bombycis genome by mediating with a non-transposon vector. Our research not only offers a strategy for research on gene function of N. bombycis but also provides an important reference for constructing genetically modified microsporidium utilized for biocontrol of pests.

Grass carp hemorrhagic disease is a common fish disease and often results in significant economic losses in grass carp aquaculture in China. This study was aimed to develop a novel oral vaccine against grass carp reovirus (GCRV). GCRV vp6 and vp7 genes with β-actin promoter of Megalobrama amblycephala and polyhedrin promoter (Ph10) of baculovirus, respectively, were cloned into plasmid pFast™-Dual to construct a vector pFast-PHVP7-AVP6, which was used to generate a recombinant baculovirus BacFish-vp6/vp7 via Bac-to-Bac system. The VP7 expression was analyzed from freeze-dried powder of the BacFish-vp6/vp7-infected silkworm pupae by western blotting, and VP6 expression was analyzed from orally vaccinated fish with the freeze-dried powder by RT-PCR. The VP6 expression was also analyzed from both CIK cells transduced with BacFish-vp6/vp7 and tissues of vaccinated fish by immunofluorescence analysis. Recombinant VP7 could be detected from the BacFish-vp6/vp7-infected silkworm pupae. Pathological changes were not observed in CIK cells transduced with BacFish-vp6/vp7, and VP6 expression was found in CIK cells. When the grass carps were orally administrated with the freeze-dried powder, vp6 gene transcription was found in blood of the vaccinated fishes and VP6 protein was observed in liver and kidney of the vaccinated fish by immunofluorescence analysis. These results indicated that vp7 gene was expressed in the BacFish-vp6/vp7-infected silkworm and vp6 gene was expressed in orally vaccinated fish with freeze-dried powder of the BacFish-vp6/vp7-infected silkworm pupae, suggesting the possibility to use the powder as an orally administrated vaccine.

Bombyxin (BBX) is an insulin-like peptide exists in the silkworm Bombyx mori. Our previous studies on the effects of inhibiting BBX-B8 expression found that BBX-B8 is important for the development of organ, reproduction and trehalose metabolism in the silkworms. In this paper, we investigated the expression profile of the BBX-B8 gene and effect of BBX-B8 overexpression on the development, body weight, silk protein synthesis and egg diapause of B. mori to further understand BBX-B8 functions. BBX-B8 gene expression could be detected in the brains, midguts, anterior silkglands, ovaries, testes, fat bodies, hemolymph, malpighian tubules and embryos by RT-PCR, however it was mainly expressed in the brain. Western blots showed that the change in BBX-B8 expression was not obvious in the brain of 1- to 4-day-old larvae of fifth instar silkworms, but expression increased substantially at 5- to 6-day-old larvae of fifth instar silkworms. Transgenic silkworms overexpressing BBX-B8 were obtained by introducing non-transposon transgenic vector pIZT-B8 containing a BBX-B8 gene driven by Orgyia pseudotsugata nucleopolyhedrovirus IE2 promoter into the genome. Development duration of the transgenic silkworms was delayed by 2.5–3.5 days. Cocoon shell weight of transgenic silkworms was reduced by 4.79 % in females and 7.44 % in males, pupal weight of transgenic silkworms was reduced 6.75 % in females and 13.83 % in males compared to non-transgenic silkworms, and 5.56–14.29 % of transgenic moths laid nondiapausing eggs. All results indicated that BBX-B8 plays an important role in the development, silk protein synthesis and egg diapause of silkworm.

A targeting vector consisting of a fusion gene of the green fluorescent protein (GFP) gene gfp and the antimicrobial peptide cecropin gene cec flanked by pieces of the 5′ and 3′ sequences of the fibroin L chain gene fib-L of the silkworm (Bombyx mori) and a negative selection DsRed marker gene driven by the baculovirus immediate early gene 1 (i.e.-1) promoter, was used to target the silkworm genome in order to explore the possibility of improving the performance of silk. A transgenic silkworm with a green fluorescent cocoon was obtained and PCR analysis of its genome confirmed that the target genes had been integrated into the silkworm genome correctly. Furthermore, in the posterior silk glands of the G6 generation transformation silkworm, a band representing the fusion protein Fib-L-GFP-Cec with a molecular mass of 68.7 kDa was detected by western blotting with an antibody against GFP. An investigation of the number of bacteria attached to a cocoon showed the transgenic silkworm cocoon possessed antibacterial properties. These results suggested the performance of silk can be improved by modifying the fibroin gene.

High-throughput paired-end RNA sequencing (RNA-Seq) was performed to investigate the gene expression profile of a susceptible Bombyx mori strain, Lan5, and a resistant B. mori strain, Ou17, which were both orally infected with B. mori cypovirus (BmCPV) in the midgut. There were 330 and 218 up-regulated genes, while there were 147 and 260 down-regulated genes in the Lan5 and Ou17 strains, respectively. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment for differentially expressed genes (DEGs) were carried out. Moreover, gene interaction network (STRING) analyses were performed to analyze the relationships among the shared DEGs. Some of these genes were related and formed a large network, in which the genes for B. mori cuticular protein RR-2 motif 123 (BmCPR123) and the gene for B. mori DNA replication licensing factor Mcm2-like (BmMCM2) were key genes among the common up-regulated DEGs, whereas the gene for B. mori heat shock protein 20.1 (Bmhsp20.1) was the central gene among the shared down-regulated DEGs between Lan5 vs Lan5-CPV and Ou17 vs Ou17-CPV. These findings established a comprehensive database of genes that are differentially expressed in response to BmCPV infection between silkworm strains that differed in resistance to BmCPV and implied that these DEGs might be involved in B. mori immune responses against BmCPV infection.

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway are involved in immune response, cell proliferation, differentiation, cell migration and apoptosis. In order to better understand the role of the JAK/STAT pathway in insects we chose Bombyx mori as an experimental model system. Over-expression of BmSTAT in a BmN cell line increased the number of cells in the G2 phase of the cell cycle. Genome-wide transcriptome analysis was performed to identify genes that were differentially expressed following BmSTAT overexpression. Transcriptome data showed that 10,853 and 10,129 expressed genes were obtained from the normal BmN cells and transformed cells, respectively. A total of 800 differentially expressed genes (DEGs) were detected, of which 787 were up-regulated and 13 were down-regulated with T test. In case of FC-test, 252 DEGs were detected, and 123 were expressed in the transformed cells and remaining were in the normal cells. Gene ontology (GO) annotation predicted a functional role for DEGs in catalytic activity, binding, transport, biological regulation, cellular and metabolic processes and pigmentation, while Kyoto encyclopedia of genes and genomes (KEGG) analysis revealed the affected genes to be involved in a multitude of cell signaling pathways. Our findings implicate JAK/STAT signaling in regulating the cell cycle in Bombyx mori, probably in combination with other pathways. These findings justify further investigation into the functional role of the BmSTAT gene.

RNA interference (RNAi)-mediated viral inhibition has been used in several organisms for improving viral resistance. In the present study, we reported the use of transgenic RNAi in preventing Bombyx mori nucleopolyhedrovirus (BmNPV) multiplication in the transgenic silkworm B. mori. We targeted the BmNPV immediate-early-1 (ie-1) and late expression factor-1 (lef-1) genes in the transiently transfected BmN cells, in the stable transformed BmN cell line and in the transgenic silkworms. We generated four piggyBac-based vectors containing short double-stranded ie-1 RNA (sdsie-1), short double-stranded lef-1 RNA (sdslef-1), long double-stranded ie-1 RNA (ldsie-1) and both sdsie-1 and sdslef-1 (sds-ie1-lef1) expression cassettes. Strong viral repression was observed in the transiently transfected cells and in the stable transformed BmN cells transfected with sds-ie-1, sdslef-1, ldsie-1 or sds-ie-lef. The decrease of ie-1 mRNA level in the sds-ie1-lef1 transiently transfected cells was most obvious among the cells transfected with different vectors. The inhibitory effect of viral multiplication was decreased in a viral dose-dependent manner; the infection ratio of transfected cells for sds-ie-1, sdslef-1, ldsie-1 and sds-ie-lef decreased by 18.83%, 13.73%, 6.93% and 30.63%, respectively, compared with control cells 5 days after infection. We generated transgenic silkworms using transgenic vector piggyantiIE-lef1-neo with sds-ie1-lef1 expression cassette; the fourth instar larvae of transgenic silkworms of generation G5 exhibited stronger resistance to BmNPV, the mortalities for the transgenic silkworms and control silkworms were 60% and 100%, respectively, at 11 days after inoculation with BmNPV (106 occlusion bodies per ml). These results suggest that double-stranded RNA expression of essential genes of BmNPV is a feasible method for breeding silkworms with a high antiviral capacity.

The Streptomyces bacteriophage, φC31, uses a site-specific integrase enzyme to perform efficient recombination. The recombination system uses specific sequences to integrate exogenous DNA from the phage into a host. The sequences are known as the attP site in the phage and the attB site in the host. The system can be used as a genetic manipulation tool. In this study it has been applied to the transformation of cultured BmN cells and the construction of transgenic Bombyx mori individuals. A plasmid, pSK-attB/Pie1-EGFP/Zeo-PASV40, containing a cassette designed to express a egfp-zeocin fusion gene, was co-transfected into cultured BmN cells with a helper plasmid, pSK-Pie1/NLS-Int/NSL. Expression of the egfp-zeocin fusion gene was driven by an ie-1 promoter, downstream of a φC31 attB site. The helper plasmid encoded the φC31 integrase enzyme, which was flanked by two nuclear localization signals. Expression of the egfp-zeocin fusion gene could be observed in transformed cells. The two plasmids were also transferred into silkworm eggs to obtain transgenic silkworms. Successful integration of the fusion gene was indicated by the detection of green fluorescence, which was emitted by the silkworms. Nucleotide sequence analysis demonstrated that the attB site had been cut, to allow recombination between the attB and endogenous pseudo attP sites in the cultured silkworm cells and silkworm individuals.

Proteomic profiles from the wing discs of silkworms at the larval, pupal, and adult moth stages were determined using shotgun proteomics and MS sequencing. We identified 241, 218, and 223 proteins from the larval, pupal, and adult moth stages, respectively, of which 139 were shared by all three stages. In addition, there were 55, 37, and 43 specific proteins identified at the larval, pupal, and adult moth stages, respectively. More metabolic enzymes were identified among the specific proteins expressed in the wing disc of larvae compared with pupae and moths. The identification of FKBP45 and the chitinase-like protein EN03 as two proteins solely expressed at the larval stage indicate these two proteins may be involved in the immunological functions of larvae. The myosin heavy chain was identified in the pupal wing disc, suggesting its involvement in the formation of wing muscle. Some proteins, such as proteasome alpha 3 subunits and ribosomal proteins, specifically identified from the moth stage may be involved in the degradation of old cuticle proteins and new cuticle protein synthesis. Gene ontology analysis of proteins specific to each of these three stages enabled their association with cellular component, molecular function, and biological process categories. The analysis of similarities and differences in these identified proteins will greatly further our understanding of wing disc development in silkworm and other insects.

The pupal stage of the silkworm Bombyx mori Linnaeus lasts for approximately two weeks. However, prolongation of pupal duration would reduce the labor required to process and dry fresh cocoons. This study investigated the effects of BmKIT3R gene (from the Chinese scorpion Buthus martensii Karsch) transfer on the pupal development of B. mori using a Gal4/UAS binary transgenic system. Gal4 driven by a pupa-specific promoter BmWCP4 (from a B. mori wing-cuticle protein gene) or PDP (from a B. mori cocoonase gene), and BmKIT3R driven by a UAS cis-acting element were used to construct novel piggyBac-derived plasmids containing a neomycin-resistance gene (neo) controlled by the Bombyx mori nucleopolyhedrovirus (BmNPV) ie-1 (immediate-early gene) promoter and a green fluorescent protein gene (gfp) under the control of the B. mori actin 3 (A3) promoter. The vector was transferred into silkworm eggs by sperm-mediated gene transfer. Transgenic silkworms were produced after screening for neo and gfp genes, and gene transfer was verified by polymerase chain reaction and dot-blot hybridization. The larval development of the hybrid progeny of Gal4- and UAS-transgenic silkworms was similar to that of normal silkworms, but some pupae failed to metamorphose into moths, and the development of surviving pupae was arrested as a result of BmKIT3R expression. Moreover, Gal4 driven by the BmWCP4 promoter delayed pupal development more effectively than that driven by the PDP promoter in the Gal4/UAS binary transgenic system. Pupal durations of hybrid transgenic silkworm progeny with BmWCP4 and PDP promoters were approximately 5, 2, and 4 days longer, respectively, compared to corresponding normal silkworms, BmWCP4/Gal4, and UAS/BmKIT3R transgenic silkworms, respectively. These results suggest new avenues of research for prolonging the pupal duration of silkworms.

To evaluate the biological activity of the posterior silk glands of transgenic silkworms expressing human insulin-like growth factor I (hIGF-I), we bred hIGF-I-transgenic silkworms through eight generations by continuously selecting with green fluorescence and G418. The G8 transgenic silkworms were confirmed by polymerase chain reaction and dot blotting, and their posterior silk glands were removed from the fifth instar larvae to make freeze-dried powders. Enzyme-linked immunosorbent assay results showed that the expression level of hIGF-I in the posterior silk glands of G8 transgenic silkworm is approximately 493 ng/g of freeze-dried powder. When the freeze-dried powder was administrated by gavage to diabetes mellitus (DM) mice, the blood glucose in DM mice significantly decreased (P < 0.05) in a time- and dose-dependent manner compared with that of DM mice orally administrated with distilled water and normal freeze-dried powders made of untreated silk glands. These results demonstrated that hIGF-I expressed in posterior silk glands of transgenic silkworms could reduce blood glucose by oral administration.

The silk gland of the silkworm is a highly specialized organ that has the wonderful ability to synthesize and secrete silk protein. To express human granucyto-macrophage colony-stimulating factor (hGM-CSF) in the posterior silk glands of gene-targeted silkworms, a targeting vector pSK-FibL-L-A3GFP-PH-GMCSF-LPA-FibL-R was constructed, harboring a 1.2 kb portion of the left homogenous arm (FibL-L), a 0.5 kb portion of the right homogenous arm (FibL-R), fibroin H-chain-promoter-driven hGM-CSF and silkworm actin 3-promoter-driven gfp. The targeting vector was then introduced into the eggs of silkworm, and the transgenic silkworms were verified by PCR and DNA hybridization after being screened for the gfp gene. Western blotting analysis using an antibody against hGM-CSF demonstrated a specific band with a molecular weight of 22 kD in the silk glands of the G3 generation transgenic silkworms. The level of expression of hGM-CSF in the posterior silk glands of the G3 generation transgenic silkworms was approximately 2.70 ng/g of freeze-dried powdered posterior silk gland. These results showed that the heterologous gene could be introduced into the silkworm genome and expressed successfully. Further more, the exogenous genes existing in the G5 transgenic silkworm identified by PCR confirmed its integration stability. In addition, the silk glands containing expressed hGM-CSF performed the function of significantly increasing leukocyte count of CY-treated mice in a time-and-dose-dependent manner.

The expression of the human insulin-like growth factor (hIGF-I) gene driven by the Fhx/P25 promoter in the silk glands of transgenic silkworms (Bombyx mori) and in transformed silkworm cells, was achieved using BmN cells transfected with a piggyBac vector, pigA3GFP-Fhx/P25-hIGF-ie-neo containing a neomycin-resistance gene (neo), a green fluorescent protein gene (gfp), an hIGF-I gene, and a helper plasmid containing the piggyBac transposase sequence under the control of the B. mori actin 3 (A3) promoter. We selected stably transformed BmN cells expressing hIGF-I using the antibiotic G418. The expression level of hIGF-I was about 450 pg in 3 × 106 cells, determined by ELISA. The piggyBac vector was transferred into the silkworm eggs using sperm-mediated gene transfer. The expression level of hIGF-I per gram fresh posterior silk glands of G4 transgenic silkworms was approx. 150 ng.

The complete nucleotide sequence of the mitogenome of Bombyx mandarina strain Qingzhou was determined. The circular genome is 15,717 bp long and has the typical gene organization and order of lepidopteran mitogenomes. All protein-coding sequences are initiated with a typical ATN codon, except the COI gene, which has a 4-bp TTAG putative initiator codon. Eleven of the 13 protein-coding gene have a complete termination codon (all TAA), but the remaining two genes terminate with incomplete codons. All transfer RNAs (tRNAs) have a clover-leaf structure typical of the mitochondrial tRNAs, and some of them have a mismatch in the four-stem-and-loop structure. The length of the A + T rich region of B. mandarina strain Qingzhou is 495 bp, shorter than that of B. mandarina strain Tsukuba (747 bp) but similar to that of Bombyx mori. Phylogenetic analysis based on the whole mitochondrial genome sequences of the available sequenced species (B. mori strains C-108, Aojuku, Backokjam, and Xiafang, B. mandarina strains Tsukuba, Ankang, and Qingzhou, and Antheraea pernyi) shows the origin of the domesticated silkmoth B. mori to be the Chinese B. mandarina. Nuclear mitochondrial pseudogene sequences were detected in the nuclear genome of B. mori with the MEGA BLAST search program. A phylogenetic analysis of these nuclear mitochondrial pseudogene sequences suggests that B. mori was domesticated independently in different areas and periods.

To express human insulin-like growth factor-I (hIGF-I) in transformed Bombyx mori cultured cells and silk glands, the transgenic vector pigA3GFP-hIGF-ie-neo was constructed with a neomycin resistance gene driven by the baculovirus ie-1 promoter, and with the hIGF-I gene under the control of the silkworm sericin promoter Ser-1. The stably transformed BmN cells expressing hIGF-I were selected by using the antibiotic G418 at a final concentration of 700–800 µg/mL after the BmN cells were transfected with the piggyBac vector and the helper plasmid. The specific band of hIGF-I was detected in the transformed cells by Western blot. The expression level of hIGF-I, determined by ELISA, was about 7800 pg in 5×105 cells. Analysis of the chromosomal insertion sites by inverse PCR showed that exogenous DNA could be inserted into the cell genome randomly or at TTAA target sequence specifically for piggyBac element transposition. The transgenic vector pigA3GFP-hIGF-ie-neo was transferred into the eggs using sperm-mediated gene transfer. Finally, two transgenic silkworms were obtained after screening for the neo and gfp genes and verified by PCR and dot hybridization. The expression level of hIGF-I determined by ELISA was about 2440 pg/g of silk gland of the transgenic silkworms of the G1 generation.

•Bmdpp and Bmdaw were mainly expressed in the hemocyte of fifth instar larvae.•The expression levels of Bmdpp and Bmdaw were regulated by BmNPV infection.•The multiplication of BmNPV was inhibited by upregulation of Bmdpp and Bmdaw.•The multiplication of BmNPV was raised with downregulation of Bmdpp and Bmdaw.Transforming growth factor (TGF)-β superfamily members inhibit Bombyx mori nucleohedrovirus (BmNPV) multiplication in silkworm are not determined. In this study, we first found that BmNPV RNA transcription and protein expression level were regulated by TGF-β members, Decapentaplegic (Bmdpp) and Dawdle (Bmdaw) in the domesticated silkworm, B. mori and silkworm ovary-derived cells. Furthermore, subcellular localization showed that Bmdpp and Bmdaw were mainly presented in cytomembrane of the cultured BmN cells. Tissues expression pattern analysis found that the highest expression levels of Bmdpp and Bmdaw genes were in the hemocyte of fifth instar larvae. During the immune response, the expression level of Bmdpp gene was elevated and Bmdaw gene was declined in BmNPV infected BmN cells and silkworm. The multiplication of BmNPV was inhibited by overexpression of Bmdpp and Bmdaw genes in BmN cells. RNA interference experiments found that the multiplication of BmNPV was raised with specific siRNAs of Bmdpp and Bmdaw genes in BmN cells. The antiviral immune pathways were not significantly regulated by the TGF-β superfamily members. Taken together, these findings provided a clue to understand the function of Bmdpp and Bmdaw gene in response to the BmNPV infection in silkworm.

•We explored different responses of the JAK/STAT, Toll, Imd, and RNAi innate immune pathways in response to different microbial challenges in silkworms.•The JAK/STAT pathway could be activated by challenge with BmNPV and BmBDV.•The Toll pathway could be most robustly induced by challenge with Beb.•The Imd pathway was mainly activated in response to infection by E. coli and Sm.•The RNAi pathway was not activated by viral infection, but could be triggered by some bacterial infections.The JAK/STAT, Toll, Imd, and RNAi pathways are the major signaling pathways associated with insect innate immunity. To explore the different immune signaling pathways triggered in response to pathogenic micro-organism infections in the silkworm, Bombyx mori, the expression levels of the signal transducer and activator of transcription (BmSTAT), spatzle-1 (Bmspz-1), peptidoglycan-recognition protein LB (BmPGRP-LB), peptidoglycan-recognition protein LE (BmPGRP-LE), argonaute 2 (Bmago2), and dicer-2 (Bmdcr2) genes after challenge with Escherichia coli (E. coli), Serratiamarcescens (Sm), Bacillus bombyseptieus (Bab), Beauveriabassiana (Beb), nucleopolyhedrovirus (BmNPV), cypovirus (BmCPV), bidensovirus (BmBDV), or Nosemabombycis (Nb) were determined using real-time PCR. We found that the JAK/STAT pathway could be activated by challenge with BmNPV and BmBDV, the Toll pathway could be most robustly induced by challenge with Beb, the Imd pathway was mainly activated in response to infection by E. coli and Sm, and the RNAi pathway was not activated by viral infection, but could be triggered by some bacterial infections. These findings yield insights into the immune signaling pathways activated in response to different pathogenic micro-organisms in the silkworm.

•LAMP can be performed using very simple laboratory equipment•CyHV-LF and CyHV-LB can shorten the reaction timeand enhanced reaction efficiency.•This study suggested CyHV-2 might be passed onto offspring by vertical transmission.In recent years, an epizootic causing severe mortality among Allogynogenetic crucian carp (ACC), designated as haemorrhagic disease of ACC gill, occurred in Yancheng city of Jiangsu province of China. Obvious haemorrhage in the gills of moribund fish and a mortality rate of 100% were observed when ACCs were artificially infected with liver homogenate from diseased fish. A herpes-like virus, with enveloped virions ranged from 170 to 220 nm in diameter, could be observed in the tissues of challenged ACCs by examination with electron microscopy. Specific products representing the polymerase and helicase genes of Cyprinid herpesvirus-2 (CyHV-2) could be amplified from the challenged fish, suggesting that the haemorrhagic disease of ACC gill was caused by infection with CyHV-2. To rapidly diagnose CyHV-2-infected fish, an easy and effective detection assay with loop-mediated isothermal amplification (LAMP) was established. The LAMP assay was more sensitive than conventional PCR and the limit of detection was approximately 100 copies of target DNA. With this LAMP assay, CyHV-2 could be detected in some asymptomatic ACCs from the epidemic area and in eggs from the diseased ACCs, suggesting that CyHV-2 could infect ACCs latently and that the virus may be passed onto offspring by vertical transmission.

To verify the effects of gain-of-function mutation of the BmKIT3R gene (from the Chinese scorpion Buthus martensii Karsch) on the development and survival rate of insects and to explore a novel strategy for pest control, the effects of BmKIT3R gene transfer on the development and survival rate of silkworms were investigated. A novel transgenic vector derived from the piggyBac transposon with the BmKIT3R gene controlled by the Bmhsp20.4 promoter was transferred into silkworm eggs. Transgenic silkworms were obtained after screening with GFP and G418 antibiotics and verification by PCR and dot hybridization. The results showed that the oviposition number decreased by 18.9%, and the hatching and final survival rates were approximately 63% and 47.5%, respectively. Some 18.9% of surviving pupae died before developing into moths in the G3 generation. A specific band corresponding to BmKIT3R was detected for transgenic silkworms by Western blotting. This indicates that the Bmhsp 20.4 promoter has constitutive expression activity. The significant decrease in the survival rate suggests that pest population numbers could be effectively controlled by using BmKIT3R gene transfer. Furthermore, it can be speculated that pupal development to moths could be blocked if BmKIT3R were specially expressed in the pupal stage and reeling with fresh cocoons was performed.

This study investigated the effects of gain of ecdysteroid UDP-glucosyltransferase (EGT) gene function mutation on the development of the silkworm, Bombyx mori. A novel piggyBac-derived plasmid containing the egt gene from B. mori nucleopolyhedrovirus (BmNPV) driven by a heat-shock protein (hsp) 23.7 promoter, with a neomycin-resistance gene (neo) controlled by the BmNPV ie-1 promoter and a green fluorescent protein gene (gfp) under the control of the B. mori actin 3 (A3) promoter was constructed. The vector was transferred into silkworm eggs by sperm-mediated gene transfer. Transgenic silkworms were produced after screening for neo and gfp genes and gene transfer was verified by polymerase chain reaction, dot-blot hybridization and western blotting. The hatching rate of G1 generation silkworm eggs was about 60% lower than that of normal silkworm eggs. The duration of the G1 generation larval period was extended, and the G2 generation pupal stage lasted four days longer than that in non-transgenic silkworms. The ecdysone blood level in G2 silkworms in the third instar molting stage was reduced by up to 90%. These results show that EGT suppressed transgenic silkworm molting, and that egt expression in egt-transgenic silkworms resulted in arrest of metamorphosis from pupae to moths.Highlights► The effects of gain of EGT gene on silkworm development were investigated. ► Sperm-mediated gene transfer was used to produce transgenic silkworm. ► G1 transgenic silkworm hatching rate was about 60% lower than the normal silkworms. ► The duration of the larval period was extended in G1 transgenic silkworms. ► Hemolymph ecdysone was reduced by up to 90% in molting stage G2 transgenic silkworms.