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Silk gland size in silkworms (Bombyx mori) affects silk output. However, the molecular mechanisms by which genes regulate silk gland size remain unclear. In this study, silk glands from three pure silkworm strains (A798, A306 and XH) with different silk gland weight phenotypes were compared using transcriptomics and proteomics to identify differentially expressed genes (DEGs) and proteins (DEPs). When comparing A798 to A306 and A798 to XH, 830 and 469 DEGs were up‐regulated, respectively. These genes were related to the gene ontology terms, metabolic process, transport activity and biosynthesis process. In addition, 372 and 302 up‐regulated differentially expressed proteins were detected in A798 to A306 and A798 to XH, respectively, related to the gene ontology terms, ribosome and protein export, ribosome and polypeptide biosynthesis processes. Moreover, combined transcriptomics, proteomics and weighted correlation network analyses showed that five genes (BGIBMGA002524, BGIBMGA002629, BGIBMGA005659, BGIBMGA005711 and BGIBMGA010889) were significantly associated with the silk gland weight. Reverse Transcription‐quantitative real‐time Polymerase Chain Reaction (RT‐qPCR) and Enzyme linked immunosorbent assay (ELISA) were used to verify the mRNA and protein expression of five genes in the silk glands and tissues of 18 silkworm strains. The results showed that four genes have higher expression levels in heavier silk glands. These genes are associated with glycogen metabolism, fatty acid synthesis and branched chain amino acid metabolism, thus potentially promoting growth and silk protein synthesis. These findings provide valuable insights into the molecular mechanisms underlying the relationship between silk gland weight and silk yield in silkworms. [ABSTRACT FROM AUTHOR]

Silkworm (Bombyx mori) is not only an economic insect but also a model organism for life science research. Bombyx mori nucleopolyhedrovirus (BmNPV) disease is a major infectious disease in the world's sericulture industry. The cocoon loss caused by this disease accounts for more than 60% of the total loss caused by all silkworm diseases. To date, there has been no effective solution for preventing and treating this disease. The most effective measure is to breed disease-resistant varieties. The quickest way to breed disease-resistant varieties is to apply genetic modification. However, this requires that we obtain disease resistance genes and know the mechanism of disease resistance. Since the discovery of disease-resistant resources in 1989, scholars in the sericulture industry around the world have been inspired to search for resistance genes. In the past two decades, with the help of multi-omics technologies, screening of resistance genes, gene localization, protein modification, virus–host interactions, etc., researchers have found some candidate genes that have been proposed to function at the cellular or individual level. Several disease-resistant varieties have been obtained and used in production through hybrid breeding, RNA interference, and genetic modification. This article summarizes and reviews the discovery of and research advances related to silkworm resistance to BmNPV. It is anticipated that the review will inspire scientific researchers to continue searching for disease resistance genes, clarify the molecular mechanism of silkworm disease resistance, and promote disease-resistant silkworm breeding. [ABSTRACT FROM AUTHOR]

We previously observed an over‐dominant silkworm heterosis of increased yield in a cross of Bombyx mori nuclear polyhydrosis virus‐resistant strain NB with a susceptible strain 306. In the present study, we found that heterosis also exists in crosses of NB with other susceptible strains, indicating it is a more general phenomenon. We performed comparative transcriptome and proteome and identified 1624 differentially expressed genes (DEGs) and 298 differentially expressed proteins (DEPs) in silk glands between parents and F1 hybrids, of which 24 DEGs/DEPs showed consistent expression at mRNA and protein levels revealed by Venn joint analysis. Their expressions are completely non‐additive, mainly transgressive and under low‐parent, suggesting recombination of parental genomes may be the major genetic mechanism for the heterosis. GO and KEGG analyses revealed that they may function in generally similar but distinctive aspects of metabolisms and processes with signal transduction and translation being most affected. Notably, they may not only up‐regulate biosynthesis and transport of silk proteins but also down‐regulate other unrelated processes, synergistically and globally remodelling the silk gland to increase yield and cause the heterosis. Our findings contribute insights into the understanding of silkworm heterosis and silk gland development and provide targets for transgenic manipulation to further increase the silk yield. [ABSTRACT FROM AUTHOR]

White cocoon is developed and used as a natural fiber, and different silkworm strains have different cocoon colors. Natural-colored cocoons are preferred by people, however, the cocoon color mainly settles on sericin and it basically falls off after reeling. Currently, there are no varieties applied to production due to the formation mechanism of cocoon color is not clear. The formation of cocoon color involves multiple gene regulations. Previous studies have shown that the main genes regulating cocoon traits are the yellow blood (Y) gene, yellow blood inhibitor (I) gene, and yellow cocoon (C) gene. Among them, the products of the Y gene and C gene have been studied, but the I gene is still unclear. In this study, the midgut tissues of the yellow (NB) and the white (306) cocoon silkworm were analyzed by whole transcriptome sequencing. The results showed that there are 1639 DE-circRNAs, 70 DE-miRNAs, and 3225 DE-mRNAs, including 1785 up-regulated genes and 1440 down-regulated genes. GO and KEGG annotation results indicated that DE-mRNAs are mainly involved in intracellular transport, signal transduction, lipid transport, and metabolic processes. Two key genes, KWMTBOMO10339 and KWMTBOMO16553, were screened out according to the annotation results, which were involved in amino acid transport and ion exchange function, respectively. The interaction analysis between ncRNA and target genes showed that there were five miRNAs regulating these two genes. The qPCR analysis showed that the I gene was down-regulated, and the miRNA expression profiles were most up-regulated. Therefore, during the yellow and white cocoon formation, KWMTBOMO10339 and KWMTBOMO16553 may be regulated by miRNA, resulting in the non-expression of KWMTBOMO10339 and KWMTBOMO16553 in yellow cocoon silkworm, and the pigment molecules can enter hemolymph from the midgut to form yellow blood, then transport to the middle silk gland to finally form yellow cocoons. [ABSTRACT FROM AUTHOR]

Melanin has been reported to have potential applications in industries such as cosmetics and food due to its anti-UV and antioxidative qualities. However, the corresponding data on its safety evaluation or biological consequences are fairly limited; such data are critical given its widespread use. The effect of different concentrations (1, 2, 3, and 4%) of melanin on growth status (larvae length and weight, cocoon weight, and morphology), the microstructure of the various tissues (fat body, silk gland, and midgut), and silk properties was studied by using the silkworm (bombyx mori) as the model organism. The weight and length of silkworm larvae fed with melanin were lower than the control, indicating that melanin appears to have a negative effect on the growth status of silkworms; however, the histophysiology analysis indicates that the cell morphologies are not changed, the XRD and FTIR spectra indicate that the secondary and crystalline structures of silks are also well preserved, and the thermogravimetric analysis and tensile test indicate that the thermal stability and mechanical properties are well maintained and even improved to some extent. Generally, it indicates that melanin has a certain inhibitory effect on the growth of silkworm larva but causes no harm to the cell microstructures or silk properties; this demonstrates that the safety of melanin as a food addictive should be considered seriously. The increase of thermal stability and mechanical properties shows that melanin may be a good chemical modifier in textile industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pigment distribution were different between yellow- and white-cocoon silkworm MSGs. • DEGs, DEPs and Co-DEGs-DEPs were identified from yellow-cocoon silkworm strains. • Key factors such as CBP and Cameo2 in BmCSTS were verified in this study. • A predominant ribosome-biogenesis regulation network functions during cocoon color formation. The human macular carotenoid transporter was firstly discovered using silkworm yellow-cocoon strains, known as Bombyx mori carotenoid selective transport system (BmCSTS). However, molecular mechanisms underlying the gene/protein expression and regulations in vivo remain elusive. Here, 620 differentially expressed genes (DEGs), 1965 differentially expressed proteins (DEPs), and 67 co-genes (namely Co-DEGs-DEPs) from yellow-cocoon silkworm middle silk glands (MSGs) were identified by RNA-Seq based transcriptome and SWATH-based proteomic analysis. Notably, previously identified CBP-alike key factors were further demonstrated significantly up-regulated in all six B. mori yellow-cocoon strains (NB, NB × 306, 306 × NB, NB × 798, 798 × NB, and XH × NB) used in this study. The GO and KEGG analysis results clustered most DEGs and DEPs into multiple biological processes including both cellular components and molecular functions, especially protein synthesis and energy-metabolic pathways. The protein–protein interaction (PPI) network analysis results further revealed a predominant ribosome-biogenesis regulation working system during silkworm yellow-cocoon color formation. Additionally, high-efficient energy production and metabolism pathways (i.e. oxidative phosphorylation and citrate cycle) were also discovered, which might facilitate key gene/protein expressions and functions in BmCSTS, such as CBP and Cameo2. [ABSTRACT FROM AUTHOR]

Abstract The widespread use of silver nanoparticles (AgNPs) has raised public concern due to their potential toxic effects on humans and the environment. Although some studies have evaluated the toxicity of nanomaterials in vertebrates, studies on their hazardous effects on insects are limited. Here we focused on different concentrations of AgNPs to silkworms, a promising model organism, to evaluate their toxic effects by omics analysis. After the silkworms were fed with 100 mg L–1 AgNPs, transcriptomics analysis showed differential expression of 43 genes: 39 upregulated and 4 downregulated. These differentially expressed genes (DEGs) were involved in the digestion process, various metabolic pathways, transmembrane transport and energy synthesis. Proteomic results for silkworms fed with 400 mg L–1 AgNPs revealed 14 significantly differentially expressed proteins: 11 downregulated and 3 upregulated. Reverse transcription–polymerase chain reaction (RT-PCR) results showed that the expression levels of eight proteins were similar to the transcription levels of their corresponding genes. As the AgNPs concentration was increased, the expression of digestive enzymes was downregulated, which damaged the silkworm tissue and suppressed the activity of the enzyme superoxide dismutase and the protein HSP 1, causing oxidative stress and the production of reactive oxygen species, which had toxic effects on the silkworm digestive system. Histopathological results showed that treatment with 400 mg L–1 AgNPs destroyed the basal lamina and the columnar cells, caused adverse effects on tissues and had the potential to induce harmful effects on the digestive system. The data presented herein provide valuable information on the hazards and risks of nanoparticle contamination. Main finding: AgNPs would downregulate some digestive enzymes, damage the tissue of midgut in silkworm, meantime induce the accumulation of reactive oxygen species which may cause oxidative stress. Graphical abstract fx1 Highlights • Silver nanoparticles at 400 mg L−1 affect the midgut structure of silkworms. • Silver nanoparticles alter the expression of genes linked to extracellular matrix receptor interactions. • Silver nanoparticles at 400 mg L−1 suppress the activity of the enzyme superoxide dismutase and the HSP 1 protein. [ABSTRACT FROM AUTHOR]

The BbRib gene participates in the infection process of Beauveria bassiana (B. bassiana). It also helps pathogenic fungi to escape and defeat the insect host immune defense system by regulating the innate immune response. However, model insects are rarely used to study the mechanism of fungal ribosomal toxin protein. In this study, BbRib protein was produced by prokaryotic expression and injected into silkworm (Bombyx mori) larvae. The physiological and biochemical indexes of silkworm were monitored, and the pathological effects of BbRib protein on immune tissues of silkworm were examined by Hematoxylin and Eosin (HE) staining. BbRib protein can significantly affect the growth and development of the silkworm, causing poisoning, destroying the midgut and fat body and producing physiological changes. The ROS stress response in the adipose tissue and cells of the silkworm was activated to induce apoptosis. These results indicated that the BbRib gene not only participates in the infection process of B. bassiana, it also helps the pathogenic fungi escape the immune system by regulating the innate immune system of the silkworm, allowing it to break through the silkworm's immune defense. This study reveals the potential molecular mechanism of BbRib protein to insect toxicity, and provides a theoretical basis and material basis for the development and use of novel insecticidal toxins. [ABSTRACT FROM AUTHOR]

Uridine diphosphate (UDP)‐glycosyltransferases (UGTs) are important metabolizing enzymes functioning by adding a sugar moiety to a small lipophilic substrate molecule and play critical roles in drug/toxin metabolism for all realms of life. In this study, the silkworm Bombyx mori UGT33D1 gene was characterized in detail. UGT33D1 was found localized in the endoplasmic reticulum (ER) compartment just like other animal UGTs and was mainly expressed in the silkworm midgut. We first reported that UGT33D1 was important to BmNPV infection, as silencing UGT33D1 inhibited the BmNPV infection in silkworm BmN cells, while overexpressing the gene promoted viral infection. The molecular pathways regulated by UGT33D1 were analysed via transcriptome sequencing upon UGT33D1 knockdown, highlighting the important role of the gene in maintaining a balanced oxidoreductive state of the organism. In addition, proteins that physically interact with UGT33D1 were identified through immunoprecipitation and mass spectrometry analysis, which includes tubulin, elongation factor, certain ribosomal proteins, histone proteins and zinc finger proteins that had been previously reported for human UGT‐interacting proteins. This study provided preliminary but important functional information on UGT33D1 and is hoped to trigger deeper investigations into silkworm UGTs and their functional mechanisms. [ABSTRACT FROM AUTHOR]

Bombyx mori nucleopolyhedrovirus (BmNPV) is the most important virus that threatens sericulture industry. At present, there is no effective treatment for BmNPV infection in silkworms, and lncRNA plays an important role in biological immune response and host-virus interaction, but there are relatively few studies in silkworms. In this study, the four midgut tissue samples of the resistance strain NB (NB) and susceptible strain 306 (306) and the NB and 306 continuously infected with BmNPV for 96 h are used for whole transcriptome sequencing to analyze the differences in the genetic background of NB and 306 and the differences after inoculation of BmNPV, and the significantly different mRNA, miRNA and lnRNA between NB and 306 after BmNPV inoculation were screened. By comparing NB and 306, 2651 significantly different mRNAs, 57 significantly different miRNAs and 198 significantly different lncRNAs were screened. By comparing NB and 306 after BmNPV inoculation, 2684 significantly different mRNAs, 39 significantly different miRNAs and 125 significantly different lncRNAs were screened. According to the significantly different mRNA, miRNA and lncRNA screened from NB and 306 and NB and 306 after virus inoculation, the mRNA-miRNA-lncRNA regulatory network was constructed before and after virus inoculation, and the BmBCAT-Bomo_chr7_8305-MSTRG.3236.2 regulatory axis was screened from them, and it was found that BmBCAT was not Bomo_chr7_8305 regulated in the genetic background, after viral infection, MSTRG.3236.2 competes for binding Bomo_chr7_8305 regulates BmBCAT. The whole transcriptome sequencing results were verified by qPCR and the time-series expression analysis was performed to prove the reliability of the regulatory network. The BmBCAT-Bomo_chr7_8305-MSTRG.3236.2 regulatory axis may play a potential role in the interaction between silkworms and BmNPV. These results provide new insights into the interaction mechanism between silkworms and BmNPV. • At present, there have been studies on small RNA regulation by using sensitive silkworm varieties, but no studies have conducted whole transcriptome analysis by comparing resistant and sensitive silkworm strans inoculated with virus. • The mRNA-miRNA-lncRNA ceRNA regulatory network was constructed, from which the BmBCAT-Bomo_chr7_8305-MSTRG.3236.2 regulatory axis was screened, and the whole transcriptome sequencing results were verified by qPCR and the time-series expression analysis was performed to prove the reliability of the regulatory network. • From the perspective of lncRNA to explain the significantly different genes, our research results may provide new clues to the molecular mechanism that reveals the interaction between silkworm and virus. [ABSTRACT FROM AUTHOR]

Interacting with cell surface attachment factors or receptors is the first step for virus infection. Glycans cover a thick layer on eukaryotic cells and are potential targets of various viruses. Bombyx mori nuclear polyhedrosis viruses (BmNPV) is a baculovirus that causes huge economic loss to the sericulture industry but the mechanism of infection is unclear. Looking for potential host receptors for the virus is an important task. In this study, we investigated the role of glycosaminoglycan (GAG) modifications, including heparan sulfate (HS) and chondroitin sulfate (CS), during BmNPV infection. Enzymatic removal of cell surface HS and CS effectively inhibited BmNPV infection and replication. Exogenous HS and CS can directly bind to BmNPV virion in solution and act as neutralizers for viral infection. Furthermore, the expression of enzymes involved in GAG biosynthesis was upregulated in the BmNPV susceptible silkworm after virus administration, but down-regulated in the resistant strain after virus treatment, suggesting that BmNPV was able to utilize host cell machinery to promote the biosynthesis of GAGs. This study demonstrated HS and CS as important attachment factors that facilitate the viral entry process, and targeting HS and CS can be an effective means of inhibiting BmNPV infection. • BmNPV infection was suppressed after cell surface heparin sulfate and chondroitin sulfate were reduced. • Heparan sulfate and chondroitin sulfate can directly bind to BmNPV in solution. • GAG biosynthesis was promoted in the susceptible silkworm but suppressed in the resistant strain upon BmNPV treatment. [ABSTRACT FROM AUTHOR]

Silk proteins are synthesized and secreted by the silk gland. The differential gene expression in it leads to different silk yield among various silkworm strains. As crucial factors, microRNAs (miRNAs) regulate protein synthesis at post-transcriptional level in silk gland. MiRNAs expression level in the silk gland of three silkworm strains (Jingsong, Lan10 and Dazao) was analyzed and 33 differentially expressed miRNAs (DEMs) were discovered between JingSong (JS) and Lan10 (L10), 60 DEMs between JS and Dazao, 54 DEMs between L10 and Dazao respectively. The DEMs target genes were predicted combing with two different methods and their functions were annotated according to gene ontology. Our previous studies showed that a batch of genes related to silk yield were identified in JS and L10 strains by comparative transcriptome and quantitative trait loci (QTL) method. Thirteen DEMs whose target genes are related to protein biosynthesis processes were screened by combining with these researches. Twelve DEMs potentially regulate nineteen genes which exist in our QTL results. Six common DEMs potentially regulate the genes in both of previous results. Finally, five DEMs were selected to verify their expression levels between JS and L10 by qRT-PCR, which showed similar difference as the results of small RNA-sequencing. MiRNAs in the silk gland may directly affect silk protein biosynthesis in different silkworm strains. In current work, we identified a batch of DEMs which potentially regulate the genes related to silk yield. Further functionally study of these miRNAs will contribute to improve varieties and boost the silk yield. Our research provides a basis for studying these miRNAs and their functions in silk production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trends of metabolite levels in silkworm hemolymph upon BmNPV treatment were revealed. • BmNPV reprogrammed metabolic pathways involving trehalose, glutamine, and tryptophan. • Tryptophan inhibited BmNPV replication while glutamine promoted it. • Trehalose and riboflavin affected BmNPV replication in a complex manner. Elucidating the mechanism of infection of Bombyx mori nuclear polyhedrosis virus (BmNPV) and host antiviral response remains a major scientific task in sericulture. Virus invasion causes a series of antiviral immune responses in the host, and successful infection leads to massive changes in the host's physiological and biochemical state. Current research mainly focuses on silkworm genes and proteins associated with viral infection and resistance, but little is known regarding the host metabolic pathways that the virus utilizes for optimal replication. In this work, key metabolites involved in viral infection were identified, including trehalose, riboflavin, tryptophan, tyrosine, and phenylalanine. The genes associated with metabolite biosynthesis and catabolism were analyzed, and their expression levels were found to be largely consistent with their respective metabolite levels before and after viral treatment in both strains. The screened metabolites were further investigated for their roles in viral replication using exogenous metabolite addition into the culture medium. The results showed that tryptophan effectively inhibited BmNPV replication, while glutamine promoted viral replication in a dose-dependent manner. Trehalose and riboflavin exhibited a complex effect on BmNPV replication. This study outlines the critical metabolites and metabolic pathways required for BmNPV to proliferate and infect the host, indicting the potential of metabolite-based treatment for viral inhibition. [ABSTRACT FROM AUTHOR]

Fluorides negatively affect the development of organisms and are a threat to human health and environmental safety. In this study, Bombyx mori N cell line (BmN) were used to explore effects of NaF on insect cells. We found that 8 h (hrs) culture with high concentration of NaF (≥1 mM) induced significantly morphological changes. Dose-response curves of 72 h continuously cultured BmN treated with NaF showed that the half inhibitory concentration (IC 50 ) value was 56.60 μM. Treatment of BmN with 100 and 300 μM of NaF induced apoptosis and necrosis. 2-D electrophoresis of whole cell extracted from BmN showed that treatment with 300 μM NaF up-regulated 32 proteins and down-regulated 11 proteins when compared with controls. We identified 5 different proteins by MALDI-TOF MS, and 4 of them were identified for the first time, including 2 up-regulated proteins (mitochondrial aldehyde dehydrogenase ALDH2 and prohibitin protein WPH) and 2 down-regulated proteins (calreticulin precursor CRT and DNA supercoiling factor SCF). These observations were further confirmed by fluorescence quantitative PCR. Together, our data suggest that these target proteins could be regarded as targets influenced by NaF and also provide clues for studies on the response metabolism pathway under NaF stress. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the molecular mechanism of silkworm resistance to BmNPV infection, we constructed a near-isogenic line (BC8) with BmNPV resistance using highly resistant (NB) and highly susceptible parental strains (306). We investigated variations in the gene expression in the midguts of BmNPV-infected BC8 and 306 at 12h pi using the microarray. 92 differentially expressed genes were identified. Real-time qPCR analysis confirmed that 10 genes were significantly up-regulated or down-regulated in the midguts of BC8 and NB compared to 306. To our knowledge, we first defined the role of the amino acid transporter and 26S proteasome in insect antiviral. However, serine protease was not completely consistent with data of reported previously in insect antiviral. The role of the 5 genes (Bm123, Bm122, COP β′, aquaporin, glycoside hydrolases) was also demonstrated in insect antiviral. Our results provided new insights into the molecular mechanism of the Bombyx mori immune response against BmNPV infection. [Copyright &y& Elsevier]

Abstract: The silkworm Bombyx mori is of great economic value. The B. mori nuclear polyhedrosis virus (BmNPV) is one of the most common and severe pathogens for silkworm. Although certain immune mechanisms exist in silkworms, most silkworms are still susceptible to BmNPV infection. Interestingly, BmNPV infection resistance in some silkworm strains is varied and naturally existing. We have previously established a silkworm strain NB by genetic cross, which is highly resistant to BmNPV invasion. To investigate the molecular mechanism of silkworm resistance to BmNPV infection, we employed proteomic approach and genetic cross to globally identify proteins differentially expressed in parental silkworms NB and 306, a BmNPV-susceptible strain, and their F1 hybrids. In all, 53 different proteins were found in direct cross group (NB♀, 306♂, F1 hybrid) and 21 in reciprocal cross group (306♀, NB♂, F1 hybrid). Gene ontology and KEGG pathway analyses showed that most of these different proteins are located in cytoplasm and are involved in many important metabolisms. Caspase-1 and serine protease expressed only in BmNPV-resistant silkworms, but not in BmNPV-susceptible silkworms, which was further confirmed by Western blot. Taken together, our data suggests that both caspase-1 and serine protease play a critical role in silkworm resistance against BmNPV infection. [Copyright &y& Elsevier]

Abstract: Silkworm hemolymph is an important defense tissue to resist bacteria and virus infections. To study the response of silkworm hemolymph in the resistance of Bombyx mori L. nucleopolyhedrovirus (BmNPV), we constructed a near-isogenic silkworm line with BmNPV resistance using highly resistant and highly susceptible parental strains. In this paper, two-dimensional gel electrophoresis (2-DE) and Matrix-Assisted Laser Desorption/Ionization (MALDI)-mass spectrometry were employed to investigate the differences of protein patterns in the hemolymph of the highly resistant, highly susceptible and near-isogenic silkworm strains after BmNPV was administrated to the larvae. A comparison between the proteomes of these three silkworm strains led us to identify two differentially expressed proteins, beta-N-acetylglucosaminidase 2 and aminoacylase. The expression levels of these proteins were higher in the BmNPV resistant strains. [ABSTRACT FROM AUTHOR]

The application of silkworm hybrids have promoted the innovation and development of agricultural technology, but the mechanism of heterosis in silkworm has not been explained clearly. In this study, the heterosis of silkworm in the aspects of body weight, silk gland and cocoon weight was investigated by means of silkworm hybridization and multi-omics approaches, including transcriptome and proteome. The results showed that heterosis of silkworm body weight, silk gland and cocoon weight was overdominant, but only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Combined analysis obtained six up-regulated genes and four down-regulated genes that were consistent both in transcriptome and proteome. Gene functional enrichment analysis indicated that most up-regulated genes and proteins were mostly related to metabolism, which led to accelerated metabolism and protein synthesis and contributing to improved heterosis. The up-regulation of 6-phosphate glucose dehydrogenase (G6PDH), phosphatidylethanolamine-binding protein (PEBP) and sHSP20.4, which are involved in metabolism, might be related to silk gland heterosis. A combination of transcriptomic and proteomic analysis was used to understand the molecular mechanism of silkworm heterosis. We found that the phenotypic traits of silkworm are overdominant, while the analysis of transcriptome and proteome showed that only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Some of the genes had unique expression in F1, which was speculated that genes under heterozygous condition may result in rearrangement and cause metabolic changes in the hybrids. Those both up-regulated in transcriptomic and proteomic analysis were found to be involved in various metabolic processes, so as to accelerate metabolism and protein synthesis, thus exhibiting heterosis. Unlabelled Image • The phenotypic traits of hybrid silkworms showed heterosis. • Most of the genes and proteins in the silk gland of hybrid silkworms were lower than parents. • Accelerated metabolism and protein synthesis in hybrid silkworms contributes to heterosis. • Heterosis may be related to the decreased expression of intracellular transport proteins. [ABSTRACT FROM AUTHOR]

• Baculovirus proliferation inhibition was observed in BmNPV-resistant silkworm strains. • Virus gene transcription was significantly inhibited in resistant silkworm tissues. • Insect innate immunity responses contribute to BmNPV resistance at varying levels. • Antiviral activity of BmSOCS2 on BmNPV proliferation inhibition evidenced in vitro. The resistance of silkworm to infection by Bombyx mori nuclear polyhedrosis virus (BmNPV) is a main focus of sericultural research. Previously, a BmNPV-resistant strain, NB, was identified among a collection of Chinese silkworm strains in our lab. To better understand the molecular mechanism of NB strain resistance, the patterns of host immune response gene transcription in resistant (NB) and susceptible (306) strains were examined. Quantative real-time PCR (qRT-PCR) revealed that multiple insect innate immune signaling pathways (Toll, Imd and JAK/STAT) were strongly activated upon infection with BmNPV. Notably, Suppressor of cytokine signaling 2 (BmSOCS2) mRNA expression was significantly up-regulated in midgut tissues of the resistant NB strain, suggesting that the BmSOCS2 gene product may be involved in host immune defense against BmNPV infection. A significant inhibition of BmNPV replication was also observed in BmN cells transfected with a vector encoding BmSOCS2. The results suggest that BmSOCS2 is a key gene involved in the resistance of the NB silkworm strain to BmNPV infection. [ABSTRACT FROM AUTHOR]

The biological functions of protein glycosylation have been increasingly recognized but not yet been very well understood, especially in lower organisms. Silkworm as a model lepidopteran insect and important economic insect, has been widely studied in life science, however, the current knowledge on the glycosylation status of its proteome is not satisfactory, and little is known about how pathogenic infections could affect the glycosylation status. This study performed large scale glycosite mapping for the silkworm Bombyx mori P50 strain, and quantitatively compared with that infected with the Bombyx mori cytoplasmic polyhedrosis virus (BmCPV). Some 400 glycoproteins were mapped in the silkworm, including N- and O-glycoproteins. Upon virus infection, the glycosylation levels of 41 N-glycopeptides were significantly changed, some of them belonging to transmembrane glycoproteins. The O-glycosylation profiles were also affected. In addition, 4 BmCPV-encoded viral proteins were found to be glycosylated for the first time, including polyhedrin, P101, VP3, and the NS protein. This study drafted a silkworm protein glycosylation map and underlined the potential impact of virus infection on glycosylation. This study reveals the characteristics of the glycoproteome in the silkworm strain P50, and quantitatively compared to that infected by the virus BmCPV, which underlines the impact of virus infection on the alteration of protein glycosylation in invertebrate species. Our findings add to the knowledge of the post translational modifications of this model organism, and also uncovered for the first time the glycosylation status of the viral proteins expressed by BmCPV. Unlabelled Image • Total N- and O-glycoproteins in silkworm strain P50 were revealed. • Alterations in glycosylation profiles were noted after BmCPV virus infection. • The glycosylation status of the BmCPV-encoded proteins was uncovered. [ABSTRACT FROM AUTHOR]

• Large scale and precision mapping of silkworm N-glycoproteome. • Silkworm O-glycoproteins are mapped with glycosylation sites and glycan compositions. • Some glycoproteins identified are unique to the virus susceptible or resistant strains. Protein glycosylation plays important roles in protein structure, function, and immune recognition, among many other activities. One of the major roles of glycans and glycoconjugates on the cell surface is acting as the receptor for outside pathogens such as viruses. During the initial stage of viral replication, viruses interact with cell membrane receptors, which are in many cases glycoproteins. Identifying such glycoproteins is essential to understanding the mechanisms of viral infection, as well as developing antiviral strategies. Silkworm is an important economic insect as well as a model organism for molecular biology, yet current knowledge on its glycoproteome is far from complete due to both analytical challenges and perceived lack of importance. In this study, we performed a large-scale glycoproteomic survey for two silkworm Bombyx mori strains 306 and NB, which are susceptible and resistant to the baculovirus Bombyx mori nucleopolyhedrovirus (BmNPV), respectively. More than 400 silkworm N- and O- glycoproteins were identified with high confidence, demonstrating that this organism employs extensive glycosylation. We mapped some glycoproteins only to the BmNPV susceptible or resistant strain, underlining the potential relationship between glycosylation and viral susceptibility. We predicted O-glycoproteins and O-glycan compositions for the first time for this organism. The variations in glycan site occupancy, as well as glycan diversity between the two silkworm strains, provide an insight into role of glycosylation in viral recognition and infection processes. [ABSTRACT FROM AUTHOR]