RESUMO

The viral cathepsin from Bombyx mori Nuclear Polyhedrosis Virus (BmNPV-Cath) is a broad-spectrum protease that participates in the horizontal transmission of this virus in silkworm by facilitating solubilization of the integument of infected caterpillars. When a B. mori farm is attacked by BmNPV, there are significant sericultural losses because no drugs or therapies are available. In this work, the structure of viral cathepsin BmNPV-Cath was used as a target for virtual screening simulations, aiming to identify potential molecules that could be used to treat the infection. Virtual screening of the Natural Products library from the Zinc Database selected four molecules. Theoretical calculations of ΔGbinding by the molecular mechanics Poisson-Boltzmann surface analysis (MM-PBSA) method indicated that the molecule Zinc12888007 (Bm5) would have high affinity for the enzyme. The in vivo infection models of B. mori caterpillars with BmNPV showed that treatment with a dose of 100 µg Bm5 dissolved in Pluronic-F127 0.02% was able to reduce the mortality of caterpillars in 22.6%, however, it did not impede the liquefaction of dead bodies. Our results suggest a role of BmNPV-Cath in generating a pool of amino acids necessary for viral replication and indicate a mechanism to be exploited in the search for treatments for grasserie disease of the silkworm.

Assuntos

RESUMO

Bombyx mori is a holometabolous insect found only in germplasm banks and morphological data related of resistance and susceptibility to diseases is important when selecting hybrids for commercial and scientific interest. This study analyzed the cytopathology of B. mori trachea to BmNPV, isolated geographically in Paraná state, Brazil. Fifth instar larvae were divided into two groups, control and inoculated; the viral suspension used was 2.4×10(7) polyhedral occlusion bodies/mL. From the second to the ninth day post-inoculation, segments of silkworm organs, containing the trachea, were processed for transmission electron microscopy. Analyses of fresh hemolymph were also performed to verify the susceptibility of the hemocytes. Signs of infection were initially detected in the hemocytes and in the tracheal cells on the second and fourth post-inoculation days, respectively. The cytopathology of the trachea showed all stages of the viral cycle, which was the same as in other tissues. Virions were detected in the basal lamina, which showed structural disorganization. So, the infection time of the hemocytes prior to trachea and the presence of virus in basal lamina, suggests that the trachea was a secondary target, infected by budded virus coming from the hemolymph.

Assuntos

RESUMO

Brazil is one of the largest silk producers in the world. The domesticated silkworm (Bombyx mori) was formally introduced into the country in the twentieth century, and the state of Paraná is the main national producer. During larval stages, B. mori can be afflicted by many different infectious diseases, which lead to substantial losses in silk production. In this work, we describe the structure and complete genome sequence of the first non-Asian isolate of Bombyx mori nucleopolyhedrovirus (BmNPV), the most important silkworm pathogen. The BmNPV-Brazilian isolate is a nucleopolyhedrovirus with singly enveloped nucleocapsids within polyhedral occlusion bodies. Its genome has 126,861 bp with a G + C content of 40.4 %. Phylogenetic analysis clustered the virus with the Japanese strain (BmNPV-T3). As expected, we have detected intra-population variability in the virus sample. Variation along homologous regions (HRs) and bro genes was observed; there were seven HRs, deletion of bro-e, and division of bro-a into two ORFs. The study of baculoviruses allows for a better understanding of virus evolution providing insight for biological control of insect pests or protection against the pernicious disease caused by these viruses.

Assuntos

RESUMO

Bombyx mori is an insect whose cocoon is used in the sericulture industry, which is an important activity in parts of southern Brazil. When parasitized by Bombyx mori nucleopolyhedrovirus (BmNPV) of the genus Alphabaculovirus (alphaBV), it develops nuclear polyhedrosis disease. In Brazil, an alphaBV was isolated from larvae of B. mori and various target tissues were identified. However, how this geographic viral isolate affects the rectum of silk moths was unknown. The rectum, a component of the cryptonephric system, acts to absorb water and mineral salts, and its importance for the metabolic balance of insects provoked interest in analyzing how it is affected by BmMNPV infection. Fifth instar B. mori larvae were inoculated with a viral suspension, and from the second to the ninth day post-inoculation, segments of the rectum (anterior and anal canal) were examined using light microscopy. The cryptonephric epithelial cells in the anterior region revealed no evidence of infection. However, from the fifth day post-inoculation, cells of the anal canal showed cytopathologies characteristic of alphaBV. Infection of the anal canal and other surrounding tissues led to tissue disorganization, with accumulation of polyhedra in the perinephric space and compartmentalization of the cryptonephric system, promoting changes in the fecal pellets, signalling physiological changes. These observations contribute to our understanding of the infectious cycle of BmMNPV in B. mori.

Assuntos

RESUMO

Alphabaculovirus is an entomopathogenic virus genus that infects Bombyx mori, which is known as the Bombyx mori multiple nucleopolyedrovirus (BmMNPV). This virus is polyorganotrophic, and a series of tissues are known as targets; however, there is currently no information regarding infection in the pylorus, the segment of the hindgut that is present in the midgut transition and is responsible for food passage control. Thus, in the present study, we aimed to analyze infection of the B. mori pylorus by BmMNPV. To do so, hybrid B. mori larvae were inoculated with a viral suspension of BmMNPV, and segments of the intestine containing the pylorus and its subdivisions, the posterior interstitial ring (PIR), pyloric cone, and pyloric valve, were dissected and processed for light microscopy on different days post inoculation. The results showed that B. mori pylorus subdivisions respond differently to infection, and the anterior area of the PIR is susceptible with these cells being the secondary infection targets. Cytological analysis revealed the presence of viroplasm in the hypertrophic nucleus, followed by the formation and development of viral polyhedra. Cytolysis occurred at the end of the infectious cycle, thereby releasing polyhedra and enabling the spread of the disease. There was no evidence of BmMNPV infection in the posterior area of the PIR, cone, or pyloric valve. These results will contribute to greater understanding of the virus infectious cycle, whose consequent epizootic disease can negatively impact this economically important insect that is used in silk production in Brazil.

Assuntos

RESUMO

In the silkworm (Bombyx mori), resistance to the Zhenjiang (China) strain of the densonucleosis virus (DNV-Z) is controlled by the recessive gene nsd-Z (non-susceptible to DNV-Z), which is linked to 7 simple-sequence repeat markers. Marker-assisted evaluation and selection of DNV-Z-resistant silkworms were used for predicting DNV-resistance in backcrossed animals. A silkworm race was bred using this method, and its economic characteristics were found to be similar to those of commercial silkworm races. These markers will therefore be useful for silkworm breeding programs and in screening for densonucleosis resistance in segregating populations.

Assuntos

RESUMO

Brazil has only one public genetic pool of Bombyx mori strains, which was established in 2005 at Universidade Estadual de Maringá, Maringá, Paraná State. This genetic bank has been maintained, and the strains have been characterized using genetic and morphological tools. The quantitative and qualitative traits, directly or indirectly related to productivity, were evaluated in 14 silkworm strains. In addition to biological and productivity analyses, DNA markers related to susceptibility to the B. mori nucleopolyhedrovirus (BmNPV) were analyzed. BmNPV is a major cause of production loss and is a serious problem for Paraná sericulture. The silkworm strains from diverse geographic origins were found to have different characteristics, including body weight, larval stage duration, cocoon weight, and other biological traits. In terms of productivity, the raw silk percentages were almost uniform, with an overall average of 16.28%. Overall, the Chinese strain C37 gave the best performance in many of the quantitative traits, and it surpassed the other strains in productivity traits. Therefore, it can be used as one of the strains that compose the elite germplasm for silkworm breeding programs. Additionally, genetic molecular markers were efficient in discriminating between B. mori strains that had been identified based on their geographical origin. We found that all Japanese strains produced a 400-bp molecular marker that has been associated with susceptibility to BmNPV.

Assuntos

RESUMO

Este artigo revisa os principais aspectos relacionados à sericicultura, que abrange a criação do Bombyx mori, popularmente conhecido como bicho-da-seda, que representa uma atividade desenvolvida principalmente nas pequenas propriedades rurais, onde predomina o trabalho familiar, representando uma alternativa importante para a melhoria da renda e, contribuindo desta forma para a diminuição do êxodo rural. Além dessas características, a sericicultura é uma atividade de baixo impacto ambiental, que contribui para o desenvolvimento sustentável do país. O presente trabalho tem por objetivo discutir a criação do bicho-da-seda e as principais doenças que acarretam perdas na produção, destacando que o melhoramento genético pode auxiliar na criação de híbridos mais resistentes à doenças e com melhor qualidade e quantidade de seda por casulo.(AU)

This article revises the main aspects related to sericulture which includes the breeding of Bombyx mori, popularly known as silkworm. It represents an activity developed mainly in small rural properties, where the family work prevails, representing an important alternative for the income improvement and, thus, contributing to the decrease of rural exodus. Besides, sericulture is an activity with low environmental impact which contributes to the sustainable development of the country. This study aims to discuss silkworm breeding and the main diseases that cause production losses, noting that genetic improvement can help breed more disease-resistant hybrids with better quality and quantity of silk by cocoon.(AU)

Este artículo revisa los principales aspectos relacionados con la sericultura, que abarca la cría del Bombyx mori, popularmente conocido como gusano de seda, que representa una actividad desarrollada principalmente en las pequeñas propiedades rurales, donde predomina el trabajo familiar, representando una alternativa importante para la mejora de renta y, contribuyendo así a reducir el éxodo rural. Además de esas características, la sericultura es una actividad de bajo impacto ambiental, que contribuye al desarrollo sostenible del país. Este trabajo pretende discutir la cría del gusano de seda y las principales enfermedades que causan pérdidas en la producción, señalando que el mejoramiento genético puede ayudar a crear híbridos más resistentes a las enfermedades y con mejor calidad y cantidad de seda por capullo.(AU)

Assuntos

RESUMO

Este artigo revisa os principais aspectos relacionados à sericicultura, que abrange a criação do Bombyx mori, popularmente conhecido como bicho-da-seda, que representa uma atividade desenvolvida principalmente nas pequenas propriedades rurais, onde predomina o trabalho familiar, representando uma alternativa importante para a melhoria da renda e, contribuindo desta forma para a diminuição do êxodo rural. Além dessas características, a sericicultura é uma atividade de baixo impacto ambiental, que contribui para o desenvolvimento sustentável do país. O presente trabalho tem por objetivo discutir a criação do bicho-da-seda e as principais doenças que acarretam perdas na produção, destacando que o melhoramento genético pode auxiliar na criação de híbridos mais resistentes à doenças e com melhor qualidade e quantidade de seda por casulo.

This article revises the main aspects related to sericulture which includes the breeding of Bombyx mori, popularly known as silkworm. It represents an activity developed mainly in small rural properties, where the family work prevails, representing an important alternative for the income improvement and, thus, contributing to the decrease of rural exodus. Besides, sericulture is an activity with low environmental impact which contributes to the sustainable development of the country. This study aims to discuss silkworm breeding and the main diseases that cause production losses, noting that genetic improvement can help breed more disease-resistant hybrids with better quality and quantity of silk by cocoon.

Este artículo revisa los principales aspectos relacionados con la sericultura, que abarca la cría del Bombyx mori, popularmente conocido como gusano de seda, que representa una actividad desarrollada principalmente en las pequeñas propiedades rurales, donde predomina el trabajo familiar, representando una alternativa importante para la mejora de renta y, contribuyendo así a reducir el éxodo rural. Además de esas características, la sericultura es una actividad de bajo impacto ambiental, que contribuye al desarrollo sostenible del país. Este trabajo pretende discutir la cría del gusano de seda y las principales enfermedades que causan pérdidas en la producción, señalando que el mejoramiento genético puede ayudar a crear híbridos más resistentes a las enfermedades y con mejor calidad y cantidad de seda por capullo.

Assuntos

RESUMO

Previous reports demonstrated that actin is necessary for nucleocapsid transport and viral gene expression during nucleopolyhedrovirus infection of Bombyx mori. The first intron of B. mori A3 actin contains a cryptic promoter that drives expression of a rare isoform. We detected differences in the size and nucleotide composition of the first intron of the A3 actin gene from B. mori strain C24A, which is more resistant to nucleopolyhedrovirus than the M11A strain (22 and 95% lethality, respectively). We sought to determine if resistance to BmMNPV infection and the A3 actin promoter structure are correlated. Intrinsically bent DNA sites in these sequences, which determine curved structures, were analyzed by electrophoretic mobility assays and the helical parameters ENDS ratio, roll and twist. We found both fragments to have non-centralized bent DNA sites with distinct ENDS ratio values, nucleotide positions and two-dimensional structures. Additionally, a conformational-sensitive gel electrophoresis assay identified an allelic variation found in strain M11A that is absent in strain C24A. These data suggest that A3 actin intronic sequence variations impair virus propagation and are markers of BmMNPV-resistant populations.

Assuntos