Bombyx Mori Research Articles

Linc20486 promotes BmCPV replication through inhibiting the transcription of AGO2 and Dicers

The silkworm holds pivotal economic importance, serving not only as a primary source of silk but also as a prominent model organism in scientific research. Nonetheless, silkworm farming remains vulnerable to diverse factors, with viral infections posing the gravest threat to the sericulture industry. Among these, the Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), a member of the Reoviridae family and the cytoplasmic polyhedrosis virus genus, emerges as a significant pathogen in silkworm production. BmCPV infection primarily induces midgut sepsis in silkworms, spreads rapidly, and can inflict substantial economic losses on sericulture production. Presently, effective strategies for preventing and treating BmCPV infections are lacking.Long non-coding RNA (lncRNA) constitutes a class of RNA molecules with transcripts exceeding 200 nt, playing a crucial role in mediating the interplay between pathogens and host cells. Investigation through high-throughput technology has unveiled that BmCPV infection markedly upregulates the expression of Linc20486. This observation suggests potential involvement of Linc20486 in regulating virus replication. Indeed, as anticipated, knockdown of Linc20486 in cells profoundly impedes BmCPV replication, whereas overexpression significantly enhances virus propagation.To probe into the mechanism underlying Linc20486′s impact on virus replication, its effects on autophagy, innate immunity, and RNAi-related pathways were scrutinized. The findings revealed that Linc20486 exerts significant influence on the expression of RNAi pathway-related genes, such as Dicer1, Dicer2 and AGO2. This discovery holds promise for unveiling novel avenues to comprehend and combat BmCPV infections in silkworms.

Binding characteristics and structural dynamics of two general odorant-binding proteins with plant volatiles in the olfactory recognition of Glyphodes pyloalis

Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is the most destructive pest, causing severe damage to mulberry production in China's sericulture industry. The insecticide application in mulberry orchards poses a significant risk of poisoning to Bombyx mori. Shifting from insecticides to odor attractants is a beneficial alternative, but not much data is available on the olfactory system of G. pyloalis. We identified 114 chemosensory genes from the antennal transcriptome database of G. pyloalis, with 18 odorant-binding protein (OBP) and 17 chemosensory protein (CSP) genes significantly expressed in the antennae. Ligand-binding assays for two antennae-biased expressed general odorant-binding proteins (GOBPs) showed high binding affinities of GOBP1 to hexadecanal, β-ionone, and 2-ethylhexyl acrylate, while GOBP2 exhibited binding to 4-tert-octylphenol, benzyl benzoate, β-ionone, and farnesol. Computational simulations indicated that van der Waal forces predominantly contributed to the binding free energy in the binding processes of complexes. Among them, Phe12 of GOBP1 and Phe19 of GOBP2 were demonstrated to play crucial roles in their bindings to plant volatiles using site-directed mutagenesis experiments. Moreover, hexadecanal and β-ionone attracted G. pyloalis male moths in the behavioral assays, while none of the candidate plant volatiles significantly affected female moths. Our findings provide a comprehensive understanding of the molecular mechanisms underlying olfactory recognition in G. pyloalis, setting the groundwork for novel mulberry pests control strategies based on insect olfaction.

Nanosensors for monitoring in sericulture: Enhancing silk production through precision technology

Over millennia, sericulture the traditional practice of raising silkworms (Bombyx mori L.) for the purpose of producing silk, has undergone substantial change. From its beginnings in China to its eventual global expansion along the Silk Road, sericulture has continued to be an important industry, producing fine silk strands that are woven into highly priced garments all over the world. But just like any agricultural venture, sericulture has to deal with issues including pest control, environmental factors, and maintaining the quality of the silk. In sericulture, traditional monitoring techniques frequently depend on manual observation and recurrent sampling, which can be labour-intensive and may not offer the real-time information needed for prompt actions. Recent advancements in nanotechnology have made it possible to develop nanosensors that can precisely and continuously monitor environmental parameters, insect presence, and silk quality a viable option to modernize sericulture's monitoring techniques. This article explores the applications, benefits, challenges, and future prospects of nanosensors for monitoring in sericulture, highlighting their potential to enhance silk production efficiency, sustainability, and economic viability.

Differential expression of fibroin-related genes in middle silk glands is induced by dietary differences in a strain-dependent manner in Bombyx mori

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.

Bombyx mori nucleopolyhedrovirus LEF-2 disrupts the cell cycle in the G2/M phase by triggering a host cell DNA damage response.

It is a common strategy for viruses to block the host cell cycle to favour their DNA replication. Baculovirus, being a double-stranded DNA virus, can arrest the cell cycle in the G2/M phase to facilitate its replication. However, the key viral genes and mechanisms crucial for inducing cell cycle arrest remain poorly understood. Here, we initially examined the impacts of several Bombyx mori nucleopolyhedrovirus (BmNPV) DNA replication-associated genes: ie1, lef-1, lef-2, lef-3, lef-4, odv-ec27 and dbp. We assessed their effects on both the host cells' DNA replication and cell cycle. Our findings reveal that when the lef-2 gene was overexpressed, it led to a significant increase in the number of cells in the G2/M phase and a reduction in the number of cells in the S phase. Furthermore, we discovered that the LEF-2 protein is located in the virogenic stroma and confirmed its involvement in viral DNA replication. Additionally, by employing interference and overexpression experiments, we found that LEF-2 influences host cell DNA replication and blocks the cell cycle in the G2/M phase by regulating the expression of CyclinB and CDK1. Finally, we found that BmNPV lef-2 triggered a DNA damage response in the host cell, and inhibiting this response removed the cell cycle block caused by BmNPV LEF-2. Thus, our findings indicate that the BmNPV lef-2 gene plays a crucial role in viral DNA replication and can regulate host cell cycle processes. This study furthers our understanding of baculovirus-host cell interactions and provides new insight into the molecular mechanisms of antiviral research.

Obtaining chitosan from chitine-containing uzbekistan raw materials and research of antimicrobial properties

The optimal conditions for the isolation of valuable natural biopolymers were revealed. chitosan from cysts of Artemia parthenogenetia in the Aral Sea and from pupae of the silkworm Bombyx mori. Chitosan (Chs) was obtained from cysts of A. parthenogenetia with a molecular weight of 89 kDa, degree of deacetylation (DDA)— 72% and solubility— 81.62%. It has been shown that it is possible to isolate Chs from silkworm pupae of sufficient purity with different molecular weights and DDA depending on the synthesis conditions and the degree of purification. Bombyx mori Chs has a higher molecular weight of 100–160 kDa, a high DDA— up to 90% and a solubility of 88%. IR spectroscopy, X-ray diffraction and elemental analysis have shown the purity of the isolated Chs from various sources. In chitin from A. parthenogenetia cysts of the Aral Sea, two types of modifications α and β with corresponding syngonies are observed, which confirms its polymorphic structure. The antibacterial activity of B. mori Chs has been shown, which tends to expand the spectrum of suppressed bacteria with increasing concentration and have a bactericidal effect on both gram-negative and gram-positive bacteria. Chs B. mori had an immunostimulating effect on living organisms, which allows us to recommend drugs based on Chs to strengthen the immune system.

Ortho-Vanillin Ameliorates Spinetoram-Induced Oxidative Stress in the Silkworm Bombyx mori: Biochemical and In Silico Insights.

This study investigates the toxic effects of the insecticide spinetoram on the model organism Bombyx mori (Linnaeus) and explores the potential ameliorative properties of O-Vanillin. Sub-lethal concentrations of spinetoram were given to silkworm larvae via oral feed, resulting in reduced body weight, larval length, and impaired cocoon characteristics. A study of the enzymatic and non-enzymatic antioxidants revealed oxidative stress in the gut, fat body, and silk gland tissues, characterized by decreased antioxidants and increased lipid peroxidation. However, post-treatment with O-Vanillin effectively mitigated these toxic effects, preserving antioxidant capacities and preventing lipid peroxidation. Additionally, O-Vanillin prevented the loss of body weight and improved cocoon characteristics. At the histological level, spinetoram exposure caused mild histological damage in the gut, fat body, and silk gland. However, O-Vanillin post-treatment had ameliorative effects and mitigated the histological damages. To delve deeper into the mechanism of amelioration of O-Vanillin, in silico studies were used to study the interaction between an important xenobiotic metabolism protein of theBombyxmori, i.e., Cytochrome p450, specifically CYP9A19, and O-Vanillin. We performed blind molecular docking followed by molecular dynamic simulation, and the results demonstrated stable binding interactions between O-Vanillin and CYP9A19, a cytochrome P450 protein in silkworm, belonging to the subfamily CYP9A, suggesting a potential role for O-vanillin in modulating xenobiotic metabolism.

In Situ ATR-FTIR Studies on the β-Sheet Formation of Native and Regenerated Bombyx mori Silk Material in Solution and Its Potential for Drug Releasing Coatings.

Dynamic attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy at both solutions and coatings of a semicrystalline silk material derived from Bombyx mori was applied to monitor the β-sheet conformation, which is known to correlate with silk protein crystallinity. The secondary structure-sensitive Amide I band was analyzed. Two silk protein samples were studied: native-based silk buffer fibroin (NSF) was extracted from silk glands and regenerated silk fibroin (RSF) was extracted from degummed cocoons. Solutions of both NSF and RSF at 2 mg/mL featured low initial β-sheet contents of 5-12%, which further increased to 47-53% after 24 h. RSF and NSF solutions at 23 mg/mL also featured low initial β-sheet contents of 9-10%, which yet only slightly increased to 16-17% after 24 h. Coatings deposited from RSF solutions showed high surface integrity (Q > 99%) after rinsing in mineralized water, enabling interfacial drug delivery applications. RSF coatings were post-treated with either formic acid (FA) or pure methanol (MeOH) vapor to showcase inducibility of crystalline domains in RSF coatings. Such coatings were loaded with the model antibiotic drugs tetracycline (TCL) and streptomycin (STRP), and the sustained release of TCL was followed in contact with (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (HEPES) buffer. RSF/TCL coatings post-treated with formic acid (FA) vapor followed by methanol (MeOH) vapor showed a significantly lower (52%) initial burst of rather hydrophobic TCL compared to untreated RSF/TCL coatings (72%), while no such significant release difference was observed for hydrophilic STRP. This was rationalized by a specific interaction between nonpolar TCL and hydrophobic crystalline RSF domains.

Growth and Color Brightness of Glofish Fed Natural and Artificial Diets In Cianjur District, West Java Province

It is known that natural feed, in addition to being preferred because it moves, also has dyes that make the color of ornamental fish more contrasting than artificial feed. The purpose of this study is to find out which type of natural feed (Silk Worm (Tubifex sp.), Daphnia sp., Frozen Blood Worm) and artificial feed, which is more effective against the growth and brightness of the color of Glofish Starfire Red, which will be carried out in August 2024-October 2024 in Cianjur Regency, West Java Province. The study was conducted using an experimental method using a Complete Random Design (RAL) with 4 treatments and 3 replicates. The treatment given is as follows: A (Research using natural feed Daphnia sp, B (Research using natural feed Bloodwarm/Chironomidae, C (Research using natural feed Tubifex sp), D (Research using artificial feed). The parameters observed were Absolute Length Growth, Absolute Weight Growth, Specific Growth Rate and Color Brightness, to analyze the color brightness of Starfire Red fish using https://redketchup.io color comparison.

Multi-omics reveals the ecological and biological functions of Enterococcus mundtii in the intestine of lepidopteran insects

Insect guts offer unique habitats for microbial colonization, with gut bacteria potentially offering numerous benefits to their hosts. Although Enterococcus has emerged as one of the predominant gut commensal bacteria in insects, its establishment in various niches within the gut has not been characterized well. In this study, Enterococcus mundtii was inoculated into the silkworm (Bombyx mori L.) to investigate its biological functions. Genome-based analysis revealed that its successful colonization is related to adherence genes (ebpA, ebpC, efaA, srtC, and scm). This bacterium did not alter the activities of related metabolic enzymes or the intestinal barrier function. However, significant changes in the gene expressions levels of Att2, CecA, and Lys suggest potential adaptive mechanisms of host immunity to symbiotic E. mundtii. Moreover, 16S metagenomics analysis revealed a significant increase in the relative abundance of E. mundtii in the intestines of silkworms following inoculation. The intestinal microbiome displayed marked heterogeneity, an elevated gut microbiome health index, a reduced microbial dysbiosis index, and low potential pathogenicity in the treatment group. Additionally, E. mundtii enhanced the breakdown of carbohydrates in host intestines. Overall, E. mundtii serves as a beneficial microbe for insects, promoting intestinal homeostasis by providing competitive advantage. This characteristic helps E. mundtii dominate complex microbial environments and remain prevalent across Lepidoptera, likely fostering long-term symbiosis between the both parties. The present study contributes to clarifying the niche of E. mundtii in the intestine of lepidopteran insects and further reveals its potential roles in their insect hosts.

PI3K-Akt-SGF1-Dimm pathway mediates the nutritional regulation of silk protein synthesis in Bombyx mori

The efficient synthesis of silk protein is heavily reliant on the ingestion of massive nutrients during the peak growth phase in the silkworm. However, the molecular mechanism of nutritional regulation of silk protein synthesis remains unknown. In this study, we investigated the impact of nutrient deficiency on the synthesis of silk protein. Nutritional deficiency led to a reduction in silk yield, accompanied by decreased levels of silk proteins and fibroin heavy chain (FibH)-activating transcription factors SGF1 and Dimm. Furthermore, insulin enhanced the protein levels of SGF1 and Dimm, which can be attenuated by specific inhibitors of PI3K. Co-immunoprecipitation analysis showed that the nutrient pathway factor protein kinase B (Akt) could interact with SGF1 protein. Knockdown of Akt reduced the phosphorylation level of SGF1 and impedes its nuclear translocation. Further studies revealed that SGF1 was directly bound to Fkh site in the 22–43 region upstream of ATG of Dimm gene to activate its transcription. In conclusion, during the peak growth phase, nutrition promotes the massive synthesis of silk protein through the PI3K-Akt-SGF1-Dimm pathway. This study offers valuable insights into the efficient synthesis of silk proteins and establishes a theoretical foundation for improving silk yield.

Physicochemical Characterization of Oil and Chitosan Extracted from Cross Breed and Bivoltine Hybrid Silkworm Pupae: A Comparative Analysis

The oil and chitosan were extracted from silkworm pupae and analysed its physicochemical properties. Oil content in silkworm pupae ranged from 26 to 28 % on a dry weight basis. Notably, female pupae had a higher oil content (27.99 %) compared to males (27.03%). Further, bivoltine hybrids exhibited a slightly higher oil content (27.65 %) than cross breeds (27.30 %). In comparison to edible oils like groundnut oil and sunflower oil, the pupal oil showed favourable results in terms of moisture content, iodine value and saponification values, indicating quality similar to edible oils. However, acid value of silkworm pupal oil (1.570 mg KOH/g oil) was lower than that of groundnut oil (3.125 mg KOH/g oil). The acid value and peroxide value were found to be lower than three in pupal oil samples, revealed that pupal oil is good for edible purposes and indicates good oxidative stability. Among the samples, Chitosan content was higher 2.526% in the cross breed (PM × CSR2) than bivoltine hybrid 2.308%. Male silkworm pupae had a higher chitin content (3.242%) compared to female pupae (3.013%) and chitosan content was also higher (2.430%) in male pupae than in female pupae (2.345%). Pupal chitosan shows better solubility (99 %), degree of deacetylation (>85%) and ash content (<1%). These physicochemical properties were achieved the desired level for utilizing the silkworm pupal oil and chitosan as commercial utilization.

Development of Aptamer-Functionalized Gold Nanoparticles as Probes in Point-of-Care Diagnostic Device for Rapid Detection of Multidrug-Resistant Bacteria in Bombyx mori L. .

The sericulture industry suffers severe crop losses due to various silkworm diseases, necessitating the development of further technologies for rapid pathogen detection. Here, we report an all-in-one portable biosensor that combines conjugated gold nanoparticles (Au NPs) with an aptamer-based lateral flow assay (LFA) platform for the real-time analysis of Mammaliicoccus sp. and Pseudomonas sp. Our platform enables sample-to-answer naked eye detection within 5 min without any cross-reactivity with other representatives of the silkworm pathogenic bacterial group. This assay was based on the sandwich-type format using a bacteria-specific primary aptamer (Apt1) conjugated with 23 nm ± 1.27 nm Au NPs as a signal probe and another bacteria-specific secondary aptamer (Apt2)-coated nitrocellulose membrane as a capture probe. The hybridization between the signal probe and the capture probe in the presence of bacteria develops a red band in the test line, whose intensity is directly proportional to the bacterial concentration. Under the optimal experimental conditions, the visual limit of detection of the strip for Mammaliicoccus sp. and Pseudomonas sp. was 1.5 × 104 CFU/mL and 1.5 × 103 CFU/mL, respectively. Additionally, the performance of the LFA device was validated by using a colorimetric assay, and the results from the colorimetric assay are consistent with those obtained from the LFA. Our findings indicate that the developed point-of-care diagnostic device has significant potential for providing a cost-effective, scalable alternative for the rapid detection of silkworm pathogens.

Evaluation of biological activity and amino acid profile of protein from Thai edible insects

Insects are one of the sources of protein for future foods. In some cultures, insects have been used as a component of traditional medicine. Moreover, some proteins from insects have also shown biological activities related to human health, such as non-communication disease treatment. In this study, the protein content, amino acid profile, and inhibitory activity against a-glucosidase, a-amylase, acetylcholinesterase, and tyrosinase of soluble protein from six species of Thai edible insects were investigated. The protein from six Thai edible insects, including Gryllus bimaculatus De Geer (Sample 1), Omphisa fuscidentalis (Sample 2), Bombyx mori L. (Sample 3), Brachytrupes portentosus (Lichtenstein 1796) (Sample 4), Acheta domesticus L. (Sample 5), and Patanga succincta (Linnaeus) (Sample 6), was extracted and evaluated for its content and biological activity. The results indicated that sample 1 yielded the highest protein content of 84.23±5.15 g/100 g which is more than the protein content of meat and dairy products. A total of eight essential amino acid contents (EAA) were found in all six edible Thai insects. The highest total EAA was obtained from Sample 2 with 37.21±1.82 g/100 g, higher than the criteria established by FAO/WHO/UNU.1985. Sample 3 yielded the highest inhibition percentage of soluble protein from edible insects against α-glucosidase. The same was true for Sample 4 for α-amylase, Sample 1 for acetylcholinesterase, and Sample 2 for tyrosinase. These results indicated the quality and functional properties of protein from six species of Thai edible insects, which may be helpful in their future exploration and application

Silkworm pupae protein-based film incorporated with Catharanthus roseus leaf extract-based nanoparticles enhanced the lipid stability and microbial quality of cheddar cheese

The study aimed to develop a silkworm pupae protein-based film for enhancing the lipid oxidative and microbial stability of cheddar cheese. The bioactive properties were imparted to the silkworm pupae protein-based film using an optimum level (2.0%) of Catharanthus roseus leaf extract-based nanoparticles (Cat-Ros-NPs) synthesised following a green method. The cheese samples were packaged within the treated film (T2, containing 2.0% Cat-Ros-NPs) and compared with control samples [control (cheese samples without any film), T0 (cheese samples within the films without any bioactive agent) and T1 {cheese samples within the films containing 2.0% C. roseus leaf extract (Cat-Ros-Ext)}] during 90 days trial (4±1 °C). The addition of bioactive agents (Cat-Ros-Ext or Cat-Ros-NPs) increased the thickness (µm) as well as density (g/ml) of the film, thereby decreasing the transmittance (%), solubility (%), moisture content (%), and water-vapour transmission rate (mg/mt2). Both the bioactive agents increased the redness (a*) and yellowness (b*) whereas decreased the brightness (L*) of the film. The films enhanced the antioxidant and antimicrobial properties of the enclosed cheese samples during storage and the highest values were recorded for the samples packed within T2 films. The cheese samples packaged within T2 and T1 films showed significantly lower values for lipid oxidation and microbial counts. This positive effect of the films (T2 and T1) was also recorded on protein oxidation (total-carbonyl content) after day 30 and sensory quality after day 60. Our results indicate the successful use of silkworm pupae protein for the development of bioactive packaging for cheddar cheese.

Impact of High Temperature (36+1oC) and Low Humidity (35+5%) on Overall Performance of Bombyx mori L.

Impact of High Temperature (36+1oC) and Low Humidity (35+5%) on Overall Performance of Bombyx mori L.

Impact of Neem Seed Extract on Mortality, Esterase and Glutathione-S-Transferase Activities in Thai Polyvoltine Hybrid Silkworm, Bombyx mori L.

Neem, a biopesticide, offers a safer alternative to the synthetic insecticides commonly used in mulberry cultivation, which can harm silkworms. This study aimed to investigate the effects of Thai neem seed extract on all instar larvae of the Thai polyvoltine hybrid silkworm, Bombyx mori L., Dok Bua strains, focusing on the mortality rate and the activities of esterase (EST) and glutathione S-transferases (GST) enzymes. Acute toxicity was assessed using the leaf-dipping method. Results showed that the mortality rate tended to be higher in younger instars than in older ones. The first instar larvae exhibited the highest mortality rate at 94%, whereas the LC50 was highest in the third instar at 5.23 mg L-1 at 72 h. This trend aligns with the activities of EST and GST, which were evaluated in the whole bodies of the first instar larvae and the midgut tissue of fifth instar larvae. As the extract concentration increased, EST activity decreased while GST activity increased in both the first and fifth instar larvae. These findings highlight that neem extract is toxic to all instar larvae, with GST playing a crucial role in detoxification, particularly in the whole body of the Thai polyvoltine hybrid silkworm.

The uncleaved signal peptide of Bombyx mori nucleopolyhedrovirus GP64 preferentially activates BmSpz7 expression, contributing to protein secretion

Bombyx mori nucleopolyhedrovirus (BmNPV) significantly impacts silkworm sericulture, causing substantial economic losses. The GP64 protein, a primary envelope protein of BmNPV budded virus (BV), retains its signal peptide (SP) in the mature form, crucial for its translocation to the plasma membrane (PM) and viral infectivity. This study investigates the role of the uncleaved SP of GP64 in activating the expression of BmSpz7, a novel Spätzle family member identified through RNA-seq analysis. We cloned and characterized BmSpz7, demonstrating its upregulated expression in BmN cells and silkworm larvae infected with BmNPV containing GP64 with an uncleaved SP. Additionally, transient expression of GP64's SP significantly enhanced BmSpz7 expression and protein secretion. These findings suggest that the uncleaved SP of GP64 plays a pivotal role in activating BmSpz7, providing new insights into the molecular interactions between BmNPV and its host, and revealing potential targets for antiviral strategies in sericulture.

Olfactory sampling volume for pheromone capture by wing fanning of silkworm moth: a simulation-based study

Odours used by insects for foraging and mating are carried by the air. Insects induce airflows around them by flapping their wings, and the distribution of these airflows may strongly influence odour source localisation. The flightless silkworm moth, Bombyx mori, has been a prominent insect model for olfactory research. However, although there have been numerous studies on antenna morphology and its fluid dynamics, neurophysiology, and localisation algorithms, the airflow manipulation of the B. mori by fanning has not been thoroughly investigated. In this study, we performed computational fluid dynamics (CFD) analyses of flapping B. mori to analyse this mechanism in depth. A three-dimensional simulation using reconstructed wing kinematics was used to investigate the effects of B. mori fanning on locomotion and pheromone capture. The fanning of the B. mori was found to generate an aerodynamic force on the scale of its weight through an aerodynamic mechanism similar to that of flying insects. Our simulations further indicate that the B. mori guides particles from its anterior direction within the ~ 60° horizontally by wing fanning. Hence, if it detects pheromones during fanning, the pheromone can be concluded to originate from the direction the head is pointing. The anisotropy in the sampling volume enables the B. mori to orient to the pheromone plume direction. These results provide new insights into insect behaviour and offer design guidelines for robots for odour source localisation.

Insights into the activation mechanism of Bm-CPA: Implications for insect molting regulation

Carboxypeptidase A has been found across various animal species, yet its activation mechanism during the insect molting process remains elusive. Our study specifically delved into the activation mechanism of carboxypeptidase A (Bm-CPA), identified in Bombyx mori's molting fluid during metamorphosis. Initially, western blotting identified two forms of Bm-CPA, 65 kDa and 54 kDa, in the epidermis of silkworms during the molting stage. Expressing the complete Bm-CPA sequence in Pichia pastoris allowed the identification, via mass spectrometry analysis, of a 75-amino-acid propeptide for the initial hydrolysis process. Subsequently, a 35 kDa form of Bm-CPA emerged in the molting fluid, confirmed as the active form through in vitro assays, demonstrating potent carboxypeptidase A activity and faint carboxypeptidase B activity. Four potential activation sites (including Lys158/Arg159 and Arg177/Arg178) were identified through mass spectrometry and amino acid mutation analysis. RNAi of Bm-CPA indicates its critical role in molting. Finally, the carboxypeptidase inhibitor (Bm-CPI) from silkworm molting fluid was expressed to explore its role in regulating Bm-CPA activity, demonstrating a direct interaction with the 35 kDa Bm-CPA. Our research implies Bm-CPA's potential involvement in the silkworm molting process, suggesting diverse regulatory roles. These findings highlight intricate protein regulation patterns during insect metamorphosis and development.