Silkworm Strains Research Articles

Effect of Environmental Temperature on Cypovirus Multiplication and Biomolecules in Silkworm Bombyx mori L.

Two strains of mulberry silkworm, namely Pure Mysore and NB4D2, at fifth instar first day were inoculated with 40ml of BmCPV suspension from the stock of 1.215 X 106 PIB/ml in 0.75% of NaCl solution by ‘oral injection’. Three batches of such inoculated worms were allowed to continue larval development at 20±1°C, 24±1°C and 30±1°C in separate BOD incubators. The crude extract of midgut tissue was prepared from the survivals and used to count the total number of polyhedra per larva in each batch. Further, during virus multiplication at different rearing temperatures, the total amount of glucose, proteins and amylase as well as succinate dehydrogenase activity levels in haemolymph were studied. The experimental results clearly indicated that the atmospheric temperature has a direct influence on a number of polyhedral formations and biomolecules.

Circadian Clock Genes Regulate Temperature-Dependent Diapause Induction in Silkworm Bombyx mori.

The bivoltine strain of the domestic silkworm, Bombyx mori, exhibits a facultative diapause phenotype that is determined by maternal environmental conditions during embryonic and larval development. Although a recent study implicated a circadian clock gene period (per) in circadian rhythms and photoperiod-induced diapause, the roles of other core feedback loop genes, including timeless (tim), Clock (Clk), cycle (cyc), and cryptochrome2 (cry2), have to be clarified yet. Therefore, the aim of this study was to elucidate the roles of circadian clock genes in temperature-dependent diapause induction. To achieve this, per, tim, Clk, cyc, and cry2 knockout (KO) mutants were generated, and the percentages of diapause and non-diapause eggs were determined. The results show that per, tim, Clk, cyc, and cry2 regulated temperature-induced diapause by acting upstream of cerebral γ-aminobutyric acid (GABA)ergic and diapause hormone signaling pathways. Moreover, the temporal expression of the clock genes in wild-type (wt) silkworms was significantly different from that of thermosensitive transient receptor potential ankyrin 1 (TRPA1) KO mutants during embryonic development. Overall, the findings of this study provide target genes for regulating temperature-dependent diapause induction in silkworms.

Identification of optimal reference genes in Bombyx mori (Lepidoptera) for normalization of stress-responsive genes after challenge with pesticides.

Pesticides are frequently used to control pests in agriculture due to their ease of use and effectiveness, but their use causes serious economic losses to sericulture when their production overlaps with agriculture. However, no suitable internal reference genes (RGs) have been reported in the study of silkworms in response to pesticides. In this study, a standard curve was established to detect the expression levels of seven RGs in different tissues of different silkworm strains after feeding with pesticides using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), including BmGAPDH, BmActin3, BmTBP, BmRPL3, Bm28sRNA, Bmα-tubulin, and BmUBC, and the stability of them was evaluated by using NormFinder, geNorm, Delta CT, BestKeeper, and RefFinder. The results showed that BmGAPDH and Bmα-tubulin were relatively stable in the midgut after feeding with fenvalerate, BmGAPDH and Bmactin3 were relatively stable in the fat body, and Bmα-tubulin and Bmactin3 were relatively stable in the hemolymph, indicating that Bmactin3 was the most suitable RG when evaluating fenvalerate, followed by BmGAPDH and Bmα-tubulin. Besides, BmGAPDH and Bmactin3 were relatively stable in the midgut after treatment with DDVP, BmGAPDH and Bmα-tubulin were relatively stable in the fat body, and BmGAPDH and Bmα-tubulin were relatively stable in the hemolymph, indicating that Bmα-tubulin was the most stable RG when evaluating DDVP, followed by BmGAPDH and Bmactin3. Of note, BmGAPDH was shared by the two pesticides. The results will be valuable for RG selection in studying the pesticide response mechanism of silkworms and other lepidopteran insects.

The Exact Timing of Microinjection of Parthenogenetic Silkworm Embryos Is Crucial for Their Successful Transgenesis.

The use of parthenogenetic silkworm (Bombyx mori) strains, which eliminate the problem of recombination, is a useful tool for maintaining transgenic clonal lines. The generation of genetically identical individuals is becoming an important tool in genetic engineering, allowing replication of an existing advantageous trait combination without the mixing that occurs during sexual reproduction. Thus, an animal with a particular genetic modification, such as the ability to produce transgenic proteins, can reproduce more rapidly than by natural mating. One obstacle to the widespread use of parthenogenesis in silkworm genetic engineering is the relatively low efficiency of downstream transgenesis techniques. In this work, we seek to optimize the use of transgenesis in conjunction with the production of parthenogenetic individuals. We found that a very important parameter for the introduction of foreign genes into a parthenogenetic strain is the precise timing of embryo microinjection. Our modification of the original method increased the efficiency of transgene injection as well as the survival rate of injected embryos. We also provide a detailed description of the methodological procedure including a graphical overview of the entire protocol.

Map-based cloning and functional analysis revealed ABCC2 is responsible for Cry1Ac toxin resistance in Bombyx mori.

Bt toxins are parasporal crystals produced by Bacillus thuringiensis (Bt).They have specific killing activity against various insects and have been widely used to control agricultural pests. However, their widespread use has developed the resistance of many target insects. To maintain the sustainable use of Bt products, the resistance mechanism of insects to Bt toxins must be fully clarified. In this study, Bt-resistant and Bt-susceptible silkworm strains were used to construct genetic populations, and the genetic pattern of silkworm resistance to Cry1Ac toxin was determined. Sequence-tagged sitemolecular marker technology was used to finely map the resistance gene and to draw a molecular genetic linkage map, and the two closest markers were T1590 and T1581, indicating the resistance gene located in the 155 kb genetic region. After analyzing the sequence of the predicted gene in the genetic region, an ATP binding cassette transporter (ABCC2) was identified as the candidate gene. Molecular modeling and protein-protein docking result showed that a tyrosine insertion in the mutant ABCC2 might be responsible for the interaction between Cry1Ac and ABCC2. Moreover, CRISPR/Cas9-mediated genome editing technology was used to knockout ABCC2 gene. The homozygous mutant ABCC2 silkworm was resistant to Cry1Ac toxin, which indicated ABCC2 is the key gene that controls silkworm resistance to Cry1Ac toxin. The results have laid the foundation for elucidating the molecular resistance mechanism of silkworms to Cry1Ac toxin and could provide a theoretical basis for the biological control of lepidopteran pests.

Mitochondrial Genome Architecture and Evolutionary Origin of the Yao Silkworm, a Living Fossil of the Domestic Silkworm Bombyx mori (Lepidoptera: Bombycidae).

The Yao silkworm is a unique silkworm resource producing yellow flat plate silk that has only been reared by the Baiku Yao ethnic group in Nandan County, Guangxi Province, China for a thousand years. Here, we report the mitochondrial genomes (mitogenomes) of five Yao silkworm strains and 10 local Guangxi strains of the domestic silkworm (Bombyx mori) L. (Lepidoptera: Bombycidae), and use the resulting mitogenomes and the available Bombyx mitogenomes to characterize their genome architecture and trace the evolutionary origin of the Yao silkworm. The five Yao silkworm mitogenomes exhibited genome architectures identical to typical set of 37 mitochondrial genes (13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs) and a high level of genome sequence similarity with the domestic silkworm. Mitogenome-based phylogenetic reconstruction provided solid evidence that the Yao silkworm shares a common ancestor with the domestic silkworm. Sliding window analysis uncovered a distinct variation pattern in the mitogenome between the Yao silkworm and the other domestic silkworm strains. The phylogenetic analyses revealed a basal placement of the Yao silkworm among all available domestic silkworm strains, indicating that the Yao silkworm is an ancient population of the domestic silkworm. Our data indicated that the Yao silkworm (B. mori) is a lineage of the domestic silkworm, which for the first time provides insights into the origin of the Yao silkworm.

Very Early Corona Treatment-Mediated Artificial Incubation of Silkworm Eggs and Germline Transformation of Diapause Silkworm Strains

Diapause is an important biological characteristic for many insect species to adapt to adverse environmental conditions and maintain the continuity of the race. Compared with the traditional hydrochloric acid or/and cold storage treatment methods, the artificial corona incubation technology of silkworm (Bombyx mori) eggs has many advantages including, the absence of pollution, easy operation and safety. However, this technology has not yet been applied in sericulture. In this study, we developed a novel artificial corona instrument to successfully disrupt the diapause of newly laid and refrigerated eggs from various Chinese and Japanese lineage silkworm strains. Subsequently, we invented a very early corona treatment (VECT) strategy to prevent the diapause of newly laid silkworm eggs within 4 h of oviposition. The hatching rates of the larvae were more than 95% in all diapause silkworm strains, which was comparable to the effect of the traditional HCl treatment strategy. In addition, we developed a combination strategy of VECT and pre-blastoderm microinjection and successfully created transgenic silkworms in various diapause strains. The results of the current study can aid in improving the corona artificial incubation technology and promote its application in sericulture.

Bacterial Survey in the Guts of Domestic Silkworms, Bombyx mori L.

Simple SummaryTo enhance the sustainability of commercial production of high-quality silk, factors that affect the economic characteristics of the silkworm and the silk it produces have been widely studied. Among these are the gut microbiota, which have been linked to absorption and utilization of nutrients, and immunity to diseases in silkworms. Because the Philippines has yet to improve the silkworm strains it currently uses for silk production, sufficient biological data, including that of microbiota, are warranted. Profiling the bacterial communities in local silkworm strains through the use of high-throughput 16S rRNA gene amplicon sequencing would be a source of useful information. Results of the 16S rRNA gene amplicon sequencing in this study showed that four of the silkworm strains reared in the Philippines are abundant in five bacterial genera, which have also been found in other silkworm strains. Results also showed that bacterial diversity and evenness increase as larvae mature, which can be correlated to larval development and to the shift in the amount and age of mulberry leaves the larvae consume.Silkworm, Bombyx mori L., research involves studies on improving strains for enhanced sustainability of high-quality silk production. Several of these have investigated the factors affecting growth and development of silkworm larvae and cocoon characteristics that subsequently affect the yield and quality of silk. The gut microbiota has been reported to impact growth and development of silkworms and has been linked, in particular, with absorption and utilization of nutrients and immunity to diseases. The silkworm strains maintained in the Philippines lack sufficient biological data for use in strain improvement. This prompted efforts to augment the data by profiling bacterial communities through high-throughput 16S rRNA gene amplicon sequencing and analysis in four of the local silkworm strains that are bred and maintained in the country. Results of the study showed that the four silkworm strains are abundant in bacteria that belong to the genera Pseudomonas, Sphingomonas, Delftia, Methylobacterium and Acinetobacter. Results also showed that bacterial diversity and evenness increase as larvae mature, which can be correlated to larval development and shifts in the amount and age of mulberry leaves the larvae consume.

Geminin is essential for DNA re-replication in the silk gland cells of silkworms

Endoreplication, known as endocycles or endoreduplication, is a cell cycle variant in which the genomic DNA is re-replicated without mitosis leading to polyploidy. Endoreplication is essential for the development and functioning of the different organs in animals and plants. Deletion of Geminin, a DNA replication licensing inhibitor, causes DNA re-replication or damage. However, the role of Geminin in endoreplication is still unclear. Here, we studied the role of Geminin in the endoreplication of the silk gland cells of silkworms by constructing two transgenic silkworm strains, including BmGeminin1-overexpression and BmGeminin1-RNA interference. Interference of BmGeminin1 led to body weight gain, increased silk gland volume, increased DNA content, and enhanced DNA re-replication activity relative to wild-type Dazao. Meanwhile, overexpression of BmGeminin1 showed an opposite phenotype compared to the BmGem1-RNAi strain. Furthermore, RNA-sequencing of the transgenic strains was carried out to explore how BmGeminin1 regulates DNA re-replication. Our data demonstrated a vital role of Geminin in the regulation of endoreplication in the silk gland of silkworms.

Transgenic genome editing-derived antiviral therapy to nucleopolyhedrovirus infection in the industrial strain of the silkworm

The silkworm (Bombyx mori) is a domesticated and economically important insect. During the whole growth period, silkworm suffers various pathogen infection. Nearly 80% of silk cocoon crop losses are attributed to viral diseases. The circular double-stranded DNA virus Bombyx mori nuclepolyhedrovirus (BmNPV) is the major viral pathogen responsible for massive silkworm death and huge economic losses in the sericulture industry. Up to now, almost all the new strategies for developing immunity against BmNPV are in laboratory strains because of the lack of transgenic technology in industrial silkworm strains. We previously demonstrated that modification of BmNPV genome DNA with the antivirus transgenic CRISPR/Cas9 system effectively improved the resistance of laboratory silkworm strains to viral pathogens. The industrial strains are monovoltine or bivoltine. It is very difficult to break the diapause before microinjection for genetic transformation. Here, we show that the anti-BmNPV transgenic CRISPR/Cas9 system also works in the industrial silkworm strain Jingsong. In this study, we successfully broke diapause and obtained generation-skipping embryos and constructed two TG Jingsong lines. Both lines exhibited significantly enhanced immunity to BmNPV without significant changes in most of the commercially important traits. These results demonstrate that the construction of TG silkworm lines carrying a heritable immune defense system against BmNPV could be an effective strategy to enhance the resistance of industrial silkworm strains to the most devastating DNA virus. The research opened a window for genetic modification of the important strains from laboratory strains to industrial strains.

Unraveling the innate immune responses of Bombyx mori hemolymph, fat body, and midgut to Bombyx mori nucleopolyhedrovirus oral infection by metabolomic analysis.

Bombyx mori nucleopolyhedrovirus (BmNPV) infection causes a series of physiological and pathological changes in Bombyx mori (B. mori). Here, a metabolomic study of the innate immunity organs including hemolymph, fat body, and midgut of the silkworm strain Dazao following BmNPV challenge was conducted to reveal the metabolic variations in B. mori. Compared to the control, 4964 and 4942 features with 4077 and 4327 high-quality features were generated under positive and negative modes, respectively, from BmNPV-infected larvae. The principal component analysis and supervised learning method using partial least squares discrimination analysis demonstrated good analytical stability and experimental reproducibility of the metabolic profiles. Based on database annotations, a total of 296, 108, and 215 differential expressed metabolites (DEMs) were identified from BmNPV-infected group of hemolymph, fat body, and midgut, respectively, which were all mainly grouped into carboxylic acids and derivatives, fatty acyls, and glycerophospholipids. Kyoto Encyclopedia of Genes and Genomes Database enrichment analysis of the DEMs showed that amino acid metabolism was increased at 24 h after BmNPV infection. BmNPV induction was adopted to significantly alter a series of immune-related pathways including phospholipase D signaling pathway, FoxO signaling pathway, metabolism of xenobiotics by cytochrome P450, melanogenesis, membrane transport, carbohydrate metabolism, and lipid metabolism. The different levels of expression of several DEMs including l-glutamate, naphthalene, 3-succinoylpyridine 1-acyl-sn-glycerol 3-phosphate, and l-tyrosine which were involved in those pathways exhibited the immune responses of B. mori to BmNPV infection. Our findings are valuable for a better understanding of the antiviral mechanism of B. mori underlying the interaction between the silkworm and BmNPV.

Fabrication of a Silk Sericin Hydrogel System Delivering Human Lactoferrin Using Genetically Engineered Silk with Improved Bioavailability to Alleviate Chemotherapy-Induced Immunosuppression.

Chemotherapy is one of the main treatments for cancer; however, it usually causes severe atrophy of immune organs and self-immunity damage to patients. Human lactoferrin (hLF) is a multiple biofunctional protein in regulating the immune response and thus holds great promise to alleviate chemotherapy-caused immunosuppression. However, a sufficient hLF resource and efficient delivery of hLF remain a challenge. Here, we provide a useful strategy to simultaneously solve these two problems. A silk sericin hydrogel system delivering recombinant hLF (SSH-rhLF) was fabricated to alleviate the chemotherapeutic drug-caused side effects by rhLF-carrying silk cocoons, which were cost-effectively produced by a transgenic silkworm strain as the resource. SSH-rhLF with a uniform porous microstructural morphology, a dominant β-sheet internal structure, adjustable concentration and sustainable release of the rhLF, and non-cytotoxicity properties was demonstrated. Interestingly, the sericin hydrogel showed effective protection of the rhLF from degradation in the stomach and small intestine, thus prolonging the bioactivity and bioavailability of rhLF. As a result, the oral administration of SSH-rhLF with a low rhLF dose showed significant therapeutic effects on enhancing the immune organs of cyclophosphamide (CTX)-treated mice by protecting the splenic follicles, promoting the expression of immunoregulatory factors, and recovering the intestinal flora family from CTX-induced imbalance, which were similar to those achieved by oral administration of a high dose of free hLF in the solution form. The results suggest that the strategy of producing rhLF silk cocoons via feeding transgenic silkworms overcomes well the shortage of rhLF resources, improves the bioavailability of oral rhLF, and alleviates the side effects of chemotherapeutic drugs on immune organs. The oral SSH-rhLF will be promising for applications in cancer chemotherapy and immunity enhancement of patients.

Comparative Transcriptome Analysis Reveals bmo-miR-6497-3p Regulate Circadian Clock Genes during the Embryonic Diapause Induction Process in Bivoltine Silkworm.

Simple SummaryDiapause is a type of seasonal polyphenism and is induced by multiple cues, such as light and temperature. However, the molecular mechanisms of how the environment induces diapause remains unclear. We are interested in the epigenetic regulation, especially the non-coding RNA, involved in environmentally induced diapause. The progeny eggs of bivoltine silkworm strains undergoing diapause or not depends on the incubation temperature during the maternal embryonic stage. In this research, we compared the differentially expressed microRNAs in embryos incubated under diapause-inducing temperature (25 °C) and non-diapause-inducing temperature (15 °C) in silkworm. Our results indicate that miRNAs respond to diapause-inducing temperature and regulate the expression of circadian clock genes. Our research not only provides reference for the study of the diapause induction process, but also gives insights into the role of epigenetic modification in diapause.Diapause is one of the survival strategies of insects for confronting adverse environmental conditions. Bombyx mori displays typical embryonic diapause, and offspring diapause depends on the incubation environment of the maternal embryo in the bivoltine strains of the silkworm. However, the molecular mechanisms of the diapause induction process are still poorly understood. In this study, we compared the differentially expressed miRNAs (DEmiRs) in bivoltine silkworm embryos incubated at diapause- (25 °C) and non-diapause (15 °C)-inducing temperatures during the blastokinesis (BK) and head pigmentation (HP) phases using transcriptome sequencing. There were 411 known miRNAs and 71 novel miRNAs identified during the two phases. Among those miRNAs, there were 108 and 74 DEmiRs in the BK and HP groups, respectively. By the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the predicted target genes of the DEmiRs, we found that aside from metabolism, the targets were also enriched in phototransduction-fly and insect hormone biosynthesis in the BK group and the HP group, respectively. Dual luciferase reporter assay illustrated that bmo-miR-6497-3p directly regulated Bmcycle and subsequently regulated the expression of circadian genes. These results imply that microRNAs, as vitally important regulators, respond to different temperatures and participate in the diapause induction process across species.

The hemolymph melanization response is related to defence against the AcMNPV infection in Bombyx mori.

Melanization is mediated by the prophenoloxidase (proPO) activation cascade and plays an important role in the arthropods immune system. Previously, we found that the hemolymph of the p50 strain does not perform melanization after infection with Autographa californica multiple nucleopolyhedrovirus (AcMNPV). However, this mechanism is still unclear. In this study, the underlying mechanism of the inhibition of hemolymph melanization was investigated by analysing the AcMNPV-susceptible or -resistant silkworm strains after inoculation with AcMNPV. The results showed that the level of hemolymph melanization was higher in resistant strain C108 than in susceptible strain p50 at the late stage (72 to 120 h postinoculation). The PO activity decreased significantly at the late stage of infection (72 to 120 hpi), and the expression of BmPPO1 and BmPPO2 was downregulated in p50. However, the PO activity increased in the resistant strain C108, while the expression level of BmPPO1 and BmPPO2 displayed no significant changes. The expression of the BmPPAE gene was upregulated in two strains during viral infection. In addition, the hemolymph melanization can weaken the viral activity in vitro. Our results suggested that the silkworm hemolymph melanization response is related to defence against the AcMNPV infection.

Stable trimer formation of spike protein from porcine epidemic diarrhea virus improves the efficiency of secretory production in silkworms and induces neutralizing antibodies in mice

Porcine epidemic diarrhea virus (PEDV) is a highly infectious pathogen of watery diarrhea that causes serious economic loss to the swine industry worldwide. Especially because of the high mortality rate in neonatal piglets, a vaccine with less production cost and high protective effect against PEDV is desired. The intrinsically assembled homotrimer of spike (S) protein on the PEDV viral membrane contributing to the host cell entry is a target of vaccine development. In this study, we designed trimerized PEDV S protein for efficient production in the silkworm-baculovirus expression vector system (silkworm-BEVS) and evaluated its immunogenicity in the mouse. The genetic fusion of the trimeric motif improved the expression of S protein in silkworm-BEVS. A small-scale screening of silkworm strains to further improve the S protein productivity finally achieved the yield of about 2 mg from the 10 mL larval serum. Mouse immunization study demonstrated that the trimerized S protein could elicit strong humoral immunity, including the S protein-specific IgG in the serum. These sera contained neutralizing antibodies that can protect Vero cells from PEDV infection. These results demonstrated that silkworm-BEVS provides a platform for the production of trimeric S proteins, which are promising subunit vaccines against coronaviruses such as PEDV.

Complete mitochondrial genome of the highly fecund Bombyx mori linnaeus, 1758 (Lepidoptera: Bombycidae) strain Jam 146

To meet the increasing demands of the society in the current era, new strains of the domesticated silkworm Bombyx mori Linnaeus, 1758 (Lepidoptera: Bombycidae) are being continuously bred. Consequently, cataloging the genetic information of pure lines is essential. The strain Jam 146, whose larvae have atypical pale, crescent-shaped body markings, is an important breeding resource due to its excellent fecundity. In this study, we sequenced the mitochondrial genome (mitogenome) of this strain using next-generation sequencing. The complete genome of this strain has a gene arrangement typical of Lepidoptera. The length of the Jam 146 mitogenome (15,661 bp) is well within the range reported in other B. mori strains, i.e. between 15,629 (Baiyun strain, China) and 15,676 bp (Hukpyobeom strain, South Korea). However, the total length of protein-coding genes, 3,733 codons in Jam 146 and two other silkworm strains previously reported from South Korea, is 13 codons longer than that in other B. mori strains. Phylogenetic analysis of 22 silkworm strains from nine countries showed that the Jam 146 strain forms a strong cluster with three other strains from China, Japan, and South Korea, suggesting that after their split from a common ancestor, the evolutionary divergence among the silkworm strains in these countries has been limited.

Identification of the in vitro antiviral effect of BmNedd2-like caspase in response to Bombyx mori nucleopolyhedrovirus infection

Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the most serious pathogens in sericulture, and the underlying antiviral mechanism in silkworm is still unclear. Bombyx mori Nedd2-like caspase (BmNc) has been identified as a candidate antiviral gene from previous transcriptome data, since it is differentially expressed in the midgut of differentially resistant silkworm strains following BmNPV infection. However, the molecular mechanism by which BmNc responds to BmNPV is unknown. In this study, the relationship between BmNc and BmNPV was confirmed by its significantly different expression in different tissues of differentially resistant strains after BmNPV infection. Moreover, the antiviral role of BmNc was confirmed by the significantly higher fluorescence signals of BV-eGFP after knockdown of BmNc in BmN cells, and a reduced signal after overexpression. This was further verified by the capsid gene vp39 expression, DNA copy number, and GP64 protein level in the RNAi and overexpression groups. Furthermore, the antiviral phenomenon of BmNc was found to be associated with apoptosis. In brief, BmNc showed a relatively high expression level in the metamorphosis stages, and the effect of BmNc on BmNPV infection following RNAi and overexpression was eliminated after treatment with the inducer, Silvestrol, and the inhibitor, Z-DEVD-FMK, respectively. Therefore, it is reasonable to conclude that BmNc is involved in anti-BmNPV infection via the mitochondrial apoptosis pathway. The results provide valuable information for elucidating the molecular mechanism of silkworm resistance to BmNPV infection.

Transcriptome reveal the response to Cry1Ac toxin in susceptible Bombyx mori.

Bombyx mori as a representative in Lepidoptera is an important economic insect in agriculture production. Bacillus thuringiensis (Bt) is a bacterial pathogen in silkworm production. Understanding how silkworm respond to Bt-toxin can provide guidance to cultivate resistant silkworm strains. Cry1Ac is one type of Bt-toxin. In current research, Dazao, a susceptible B. mori strain to Bt-toxin, was treated by Cry1Ac toxin and compared its transcriptome with untreated samples. This analysis detected 1234 differentially expressed genes (DEGs). Gene Ontology, KEGG, and UniProt keyword enrichment analysis showed that DEGs include ATP-binding cassette (ABC) transporter, stress response, cuticle, and protein synthesis, and folding process. Five ABC genes were upregulated after Cry1Ac treatment including ABCA2, ABCA3, and ABCC4. They are also known as the transporters of Bt-toxin in lepidopteran insect. Expression of cuticle proteins was significantly increased at 6 h after Cry1Ac treatment. Sex-specific storage-proteins and heat shock protein were also upregulated in Cry1Ac treated samples. Our data provide an expression profile about the response of Cry1Ac toxin in susceptible B. mori strain.

Comparisons in temperature and photoperiodic-dependent diapause induction between domestic and wild mulberry silkworms

The bivoltine strain of the domestic silkworm, Bombyx mori, has two generations per year. It shows a facultative diapause phenotype determined by environmental conditions, including photoperiod and temperature, and nutrient conditions during embryonic and larval development of the mother. However, it remains unclear how the environmental signals received during development are selectively utilized as cues to determine alternative diapause phenotypes. We performed a comparative analysis between the Kosetsu strain of B. mori and a Japanese population of the wild mulberry silkworm B. mandarina concerning the hierarchical molecular mechanisms in diapause induction. Our results showed that for the Kosetsu, temperature signals during the mother’s embryonic development predominantly affected diapause determination through the thermosensitive transient receptor potential ankyrin 1 (TRPA1) and diapause hormone (DH) signaling pathways. However, embryonic diapause in B. mandarina was photoperiod-dependent, although the DH signaling pathway and thermal sensitivity of TRPA1 were conserved within both species. Based on these findings, we hypothesize that TRPA1-activated signals are strongly linked to the signaling pathway participating in diapause induction in Kosetsu to selectively utilize the temperature information as the cue because temperature-dependent induction was replaced by photoperiodic induction in the TRPA1 knockout mutant.

Differences in prostaglandin e-related factors between silkworm strains [lepidoptera: Bombycidae] producing small eggs (d32) and giant eggs (d20)

Differences in prostaglandin e-related factors between silkworm strains [lepidoptera: Bombycidae] producing small eggs (d32) and giant eggs (d20)