BmNPV is a pathogen that infects silkworms exclusively. Although the interaction between BmNPV and the silkworm has been widely noticed and studied, its specific mechanism has still not been ...elucidated. In this study, we investigated whether BmNPV infection induces the onset of host cell autophagy to enhance viral replication. We observed a significant increase in double- or single-membrane vesicles and an accumulation of enhanced green fluorescent protein eGFP-ATG8 spots in virus-infected cells 72 h after BmNPV infection, accompanied by a conversion of ATG8 to ATG8-PE. In addition, we observed changes in the mitochondrial morphology of BmN cells after BmNPV infection by transmission electron microscopy. By detecting the mitochondrial membrane potential, we found that BmNPV infection resulted in the decrease of mitochondrial membrane potential, and that eGFP-ATG8 was able to co-localise with mitochondria after virus infection of the cells. Moreover, the use of drugs to regulate the occurrence of autophagy affects the replication of cellular BmNPV. Our data demonstrates that BmNPV infection induces host cell autophagy and leads to cellular mitochondrial damage, which in turn may lead to mitochondrial autophagy, and that BmNPV-induced host autophagy promotes its replication in cells. These findings will provide clues for further understanding of host-virus interactions.
Papers collected in the present Special Issue relate to the field of sericulture. They cover different aspects based on a very ancient human agricultural activity, taking into consideration classical ...agronomic aspects, such as the impact of feeding on silk quality and sericulture in different parts of the world. Nonetheless, cutting edge topics are addressed as well, with papers studying silk as a biomaterial, the silkworm as a model organism, and the possibility of exploring its physiology and the molecular mechanisms that stand behind it with the aid of modern tools such as gene profiling, the CRISPR/Cas-9 system, and -omics sciences.
Display omitted
•Diet and strain affect silk gland gene expression in the late fifth instar silkworm.•Diet affects fibroin-related gene expression in the middle silk gland.•Artificial diet ...upregulates the sericin gene in the posterior silk gland.
The silkworm (Bombyx mori) is a model organism for lepidopteran insects. It is an oligophagous insect that primarily feeds on mulberry leaves and has industrial use for the production of raw silk. The development of artificial diets has provided an alternative nutrient source for silkworms; however, one significant issue is that the production of cocoons is lower in silkworms reared on artificial diets compared with those reared on mulberry leaves. The differences in the silk gland in the late-stage fifth instar silkworm larvae, when silk synthesis is most active, between those raised on artificial diets and mulberry leaves, are unknown. In this study, we identified differences in the transcriptomes of the middle and posterior silk glands of fifth instar day five silkworm larvae reared on artificial diets compared with those reared on mulberry leaves using three strains: Daizo, Nichi01, and J137 × C146. We found that the silk-related genes fibrohexamerin (fhx), fibroin-light-chain (fibL), and fibroin-heavy-chain (fibH) in the middle silk gland, and ser1 in the posterior silk gland, were differentially expressed in a strain-dependent manner. In silkworms reared on artificial diets, fhx, fibL, and fibH in the middle silk gland were upregulated in Nichi01 and downregulated in J137 × C146, whereas ser1 in the posterior silk gland was upregulated in J137 × C146 compared with silkworms reared on mulberry leaves. Our results demonstrate that the diet and strain of silkworm larvae affect the expression of genes related to silk production in their silk glands during the late fifth instar stage.
Display omitted
•L. monocytogenes and Salmonella were not reported in Bombyx mori.•B. cereus and Enterobacteriaceae were reported in edible silkworm.•Allergic reactions are likely in sensitive ...individuals eating edible silkworm.•Toxicity to Bombyx mori extracts was not observed in animal studies.•As, Cu and, Zn can accumulate in Bombyx mori.
Bombyx mori (BM) is an economically important insect for silk production, and it is also farmed and used as food in different countries around the world. The present systematic review aims to assess the suitability of BM as an edible insect, retrieving data from scientific papers reporting microbiological, chemical, and allergenic hazards of silkworm consumed as either whole insects or insect derivatives. We considered all studies published in peer-reviewed journals in English, French, and Spanish languages. No time limits were imposed. We searched PUBMED, WEB of Science Core Collection, and EMBASE databases. The last literature search was carried out on May 5th, 2021. Data were collected in pre-defined tabular forms for the aforementioned hazards. In total, 65 records investigating the safety aspects were included after screening: 32 on microbiological hazards; 27 on chemical hazards; 16 on allergenic hazards. Concerning microbiological aspects, a high presence of Enterococcus in raw insects (5.00 % to 70.10 %) was reported through metagenomic analysis. Through non-metagenomic methods (classical and biomolecular microbiology techniques), Bacillus cereus and Pseudomonas fluorescens were the most commonly investigated and detected bacteria in the unprocessed insects, while B. cereus and Enterobacteriaceae were studied and reported in insect-based food. The foodborne pathogens Listeria monocytogenes and Salmonella spp. were never detected.
Concerning toxicological aspects, three studies assessed the toxicity of BM powder in laboratory animals, but no negative effects were observed. Regarding heavy metal bioaccumulation in BM, evidence was reported for As, Cu, and, Zn.
Allergic reactions following the ingestion of BM or derivative products are due to proteins that are widespread in arthropods. Furthermore, BM proteins can undergo possible cross-reactions with proteins of other insect species or crustaceans. However, heat treatments do not seem to reduce the allergenic potential of the silkworm proteins.
The major limitation of the present review is that we could include only scientific literature published in Western languages, while the majority of relevant studies were conducted in Asian countries and part of them are published in Asian languages.
In conclusion, scientific evidence regarding microbiological and chemical hazards of BM relevant for food safety is very limited. In the present work microbiological and chemical hazards relevant for food safety were identified in BM, however their presence do not impair the use as food but suggest the need for a risk assessment under specific conditions of production and use. Allergic reactions are possible in sensitive individuals following the ingestion of edible BM.
Eicosanoids are crucial downstream signals in the insect immune responses. Phospholipase A2 (PLA2) catalyzes phospholipids, the initial step in eicosanoid biosynthesis. In mammals, the biological ...roles of Ca2+-independent Phospholipase A2 (iPLA2) have been extensively studied; however, only a few studies have attempted to explore iPLA2 functions in insects. In this study, we identified two iPLA2 genes (designated as BmiPLA2A and BmiPLA2B) in the silkworm, Bombyx mori. BmiPLA2A had a 2427 base pair (bp) open reading frame (ORF) that coded for a protein with 808 amino acids. In contrast, BmiPLA2B had a 1731 bp ORF that coded for a protein with 576 amino acids. Domain analysis revealed that BmiPLA2A had six ankyrin repeat domains, but BmiPLA2B lacks these domains. BmiPLA2A and BmiPLA2B were transcribed widely in various tissues and developmental stages with different expression patterns. The administration of 20-hydroxyecdysone increased their expression levels in the epidermis and hemocytes. Furthermore, challenged with virus, fungus, Gram-negative bacteria, and Gram-positive bacteria induced the expression of BmiPLA2A and BmiPLA2B with variable degrees along with different time points. Our findings imply that BmiPLA2A and BmiPLA2B may have important biological roles in the development and innate immunity of B. mori.
More than 400 million years of natural selection acting throughout the arthropoda has resulted in highly specialized and energetically efficient processes to produce protein-based fibers with ...properties that are a source of inspiration for all. As a result, for over 80 years researchers have been inspired by natural silk production in their attempts to spin artificial silks. While significant progress has been made, with fibers now regularly outperforming silkworm silks, surpassing the properties of superior silks, such as spider dragline, is still an area of considerable effort. This review provides an overview of the different approaches for artificial silk fiber spinning and compares all published fiber properties to date which has identified future trends and challenges on the road towards replicating high performance silks.
Wild silkworms survive in environmental habitats in which temperature and humidity vary based on the weather. In contrast, domesticated silkworms live in mild environments where temperature and ...humidity are generally maintained at constant levels. Previous studies showed that the mechanical strengths and molecular orientation of the silk fibers reeled from domesticated silkworms are significantly influenced by the reeling speed. Here, we investigated the effects of reeling speed on the mechanical properties of eri silk fibers produced by wild silkworms, Samia cynthia ricini, which belong to the family of Saturniidae. We found that the structural, morphological and mechanical features of eri silk fibers are maintained irrespective of the reeling speed, in contrast to those of domesticated silkworm silk fibers. The obtained results are useful not only for understanding the biological basis underlying the natural formation of silk fibers but also for contributing to the design of artificial spinning systems for producing synthetic silk fibers.
Display omitted
Silkworm pupa protein (SPP) that obtained by traditional method usually had a high fat content, which would impose restrictions on the further use of SPP. Herein, various ...functionalized ionic liquids (ILs) were used to extract SPP from silkworm pupae, the structure-performance relationship of ILs with their SPP separation performance were explored at the same time. The research showed that the maximum extraction yield of SPP was up to 62.6% with less than 0.5% low fat content by using 1-ethyl-3-methylimidazolium chloride (EmimCl), when the dissolution experiment was conducted at 90 °C for 24 h with ethanol bath as the regeneration solvent. Comparing with the structure of raw material, the regenerated SPP maintained the native protein backbone. Meanwhile, all regenerated SPP showed a decreased crystallinity, which also exhibited decreased fraction of the α-helix comparing to that β-sheet united with coil random structures.
Noroviruses (NoVs) are one of the major causes of acute viral gastroenteritis in humans. Virus-like particles (VLPs) without genomes that mimic the capsid structure of viruses are promising vaccine ...candidates for the prevention of NoVs infection. To produce large amounts of recombinant protein, including VLPs, the silkworm-expression vector system (silkworm-BEVS) is an efficient and powerful tool. In this study, we constructed a recombinant baculovirus that expresses VP1 protein, the major structural protein of NoV GII.4. Expression analysis showed that the baculovirus-infected silkworm pupae expressed NoV VP1 protein more efficiently than silkworm larval fat bodies. We obtained about 4.9 mg of purified NoV VP1 protein from only five silkworm pupae. The purified VP1 protein was confirmed by dynamic light scattering and electron microscopy to form VLPs of approximately 40 nm in diameter. Antisera from mice immunized with the antigen blocked NoV VLPs binding to histo-blood group antigens of pig gastric mucin and also blocked NoV infection in intestinal epithelial cells derived from human induced pluripotent stem (iPS) cells. Our findings demonstrated that NoV VLP eliciting protective antibodies could be obtained in milligram quantities from a few silkworm pupae using the silkworm-BEVS.
Viral diseases pose a significant threat to livestock husbandry and plant cultivation. CRISPR/Cas9-mediated targeted editing of viral genes offers a promising approach to antiviral therapy. The ...silkworm, Bombyx mori, is an economically important insect susceptible to infection by B. mori nucleopolyhedrovirus (BmNPV), and viral outbreaks cause severe economic losses to the sericulture industry. Here, we identified BmNPV orf76 as a viral late gene that is highly similar to Autographa californica multiple nucleopolyhedrovirus Ac93. The deletion of orf76 abolished BmNPV proliferation and hindered the production of infectious budded viruses. We generated a transgenic line, Cas9(+)/sgorf76(+), that did not affect the growth or development of the silkworm and demonstrated that the transgenic line Cas9(+)/sgorf76(+) efficiently cleaved orf76 at the sgorf76 site, resulting in large deletions at 120 h post-infection, with no observed off-target effects. Survival analyses revealed that the transgenic line Cas9(+)/sgorf76(+) exhibited significantly higher survival rates than the control lines Cas9(−)/sgorf76(−), regardless of the BmNPV inoculation dose. Additionally, the number of BmNPV DNA copies and the expression levels of viral genes were markedly inhibited in the transgenic line Cas9(+)/sgorf76(+) compared with the control line Cas9(−)/sgorf76(−). The results provide a promising target for Cas9-mediated antiviral therapy against BmNPV, and the findings provide new insights for baculovirus gene function studies and lepidopteran pest control.
•BmNPV orf76 is a viral late gene and its sequence similarity varies widely among different species.•Deletion of orf76 abolished BmNPV proliferation.•Transgenic line Cas9(+)/sgorf76(+) efficiently and specifically cleaved orf76 to improve viral resistance against BmNPV.
PDF
