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

Ribosomal protein L13 (RPL13) is highly conserved in evolution. At present, the properties and functions of RPL13 have not been characterised in insects. In this study, Bombyx mori RPL13 (BmRPL13) was first found to be specifically recruited to the sites of ultraviolet (UV)‐induced DNA damage and contributed to UV damage repair. Escherichia coli expressing BmRPL13 showed better resistance to UV radiation. After knocking down the expression of BmRPL13 in BmN cells, the repair speed of UV‐damaged DNA slowed down. The further results showed that BmRPL13 interacted with B. mori nucleopolyhedrovirus (BmNPV) ORF65 (Bm65) protein to locate at the UV‐induced DNA damage sites of BmNPV and helped repair UV‐damaged viral DNA. [ABSTRACT FROM AUTHOR]

Diagram illustrating the potential mechanism of BmNPV infection in the 306 strain. The three-color modules represent distinct signaling pathways: NF-kB (depicted in purple), MAPK (illustrated in green), and JAK/STAT (highlighted in pink). Genes outlined in red signify upregulation, while those outlined in green denote downregulation. Genes outlined in black represent expression levels of uncertainty. Illustrations were generated using BioRender. [Display omitted] • Integration of third-generation and second-generation high-throughput sequencing technologies for precise identification and analysis of alternative splicing (AS) patterns. • Identification of five pivotal genes (Dsclp, LOC692903, LOC101743583, LOC101742498, LOC101743809) associated with the response to BmNPV infection. • Discovery of novel transcripts, expanding the current understanding beyond what is available in SilkBase. The silkworm, Bombyx mori, stands out as one of the few economically valuable insects within the realm of model organisms. However, Bombyx mori nucleopolyhedrovirus (BmNPV) poses a significant threat, decreasing the quality and quantity of silkworm cocoons. Over the past few decades, a multitude of researchers has delved into the mechanisms that underlie silkworm resistance to BmNPV, employing diverse methodologies and approaching the problem from various angles. Despite this extensive research, the role of alternative splicing (AS) in the silkworm's response to BmNPV infection has been largely unexplored. This study leveraged both third-generation (Oxford Nanopore Technologies) and second-generation (Illumina) high-throughput sequencing technologies to meticulously identify and analyze AS patterns in the context of BmNPV response, utilizing two distinct silkworm strains—the susceptible strain 306 and the resistant strain NB. Consequently, we identified five crucial genes (Dsclp , LOC692903, LOC101743583, LOC101742498, LOC101743809) that are linked to the response to BmNPV infection through AS and differential expression. Additionally, a thorough comparative analysis was conducted on their diverse transcriptomic expression profiles, including alternative polyadenylation, simple sequence repeats, and transcription factors. [ABSTRACT FROM AUTHOR]

The silkworm Bombyx mori ( B. mori ), a lepidopteran model organism, has become an important model for molecular biology researches with its genome completely sequenced. Silkworms confront different types of virus diseases, mainly including those caused by Bombyx mori nucleopolyhedrovirus (BmNPV), Bombyx mori densovirus type 1 (BmDNV-1), Bombyx mori bidesovirus (BmBDV) which was termed as Bombyx mori densovirus type 2 (BmDNV-2) or Bombyx mori parvo-like virus (BmPLV) before in sericulture. B. mori offers excellent models to study the molecular mechanisms of insect innate immune responses to viruses. A variety of molecules and pathways have been identified to be involved in the immune responses in the silkworm to viruses, such as the antimicrobial peptides, prophenoloxidase-activating system, apoptosis, ROS, small RNA and related molecules. Here in this review, we summarize the current research advances in molecules involved in silkworm anti-virus pathways. Moreover, taking BmNPV as an example, we proposed a schematic model of molecules and pathways involved in silkworm immune responses against virus infection. We hope this review can facilitate further study of antiviral mechanisms in silkworm, and provide a reference for virus diseases in other organisms. [ABSTRACT FROM AUTHOR]

It is unclear how, or to what extent, baculovirus DNA that has been damaged by ultraviolet (UV) light is repaired during infection and replication. In our previous study, expression of Bombyx mori nucleopolyhedrovirus (BmNPV) ORF Bm65, a homolog of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac79, correlated with decreased inactivation of virus by UV irradiation. In the current study, we accumulated more evidence pointing to a role for Bm65 in repair of UV-induced DNA damage. The localization of Bm65 was studied using enhanced green fluorescent protein (EGFP) fusion constructs expressed in BmN cells transfected with a Bm65 expression plasmid. The results indicate that Bm65-EGFP accumulates in the nucleus. A host cell reactivation assay showed that Bm65 significantly increased the expression of UV-damaged mCherry reporter gene. An assay measuring cyclobutane pyrimidine dimers (CPDs) in UV-irradiated BmN cells found that CPD quantity was decreased in cells transfected with a Bm65 expression plasmid. We also showed that after UVC treatment, the viability of Bm65-transfected cells was higher than that of egfp-transfected cells. These results suggest that Bm65 may be involved in the repair of baculovirus DNA that has been damaged by UV light. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar ultraviolet radiation (UV) can cause DNA damage in microorganisms. Flap endonuclease 1 (FEN1) is a structure-specific nuclease and plays important roles in DNA replication and repair. At present, the properties and functions of FEN1 have not been characterized in detail in invertebrates such as Bombyx mori. In this study, Bombyx mori FEN1 (BmFEN1) was expressed in E. coli, and was shown to have nuclease activity that nonspecifically cleaved DNA in vitro. However, inside the cell, BmFEN1 did not cleave DNA randomly. Truncated BmFEN1 missing the nuclear localization signal (346–380 aa) still had the nuclease activity, but was no longer precisely localized to the sites of UV-induced DNA damage. It was further found that BmFEN1 favored the faster repair of UV-damaged DNA. The present study will provide a reference for further understanding the functions of BmFEN1 and UV-induced DNA damage repair mechanisms in insects. [ABSTRACT FROM AUTHOR]