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Transcriptome analysis of molting variation in dominant trimolter silkworms, Bombyx mori

ABSTRACT: Silkworm (Bombyx mori) is a holometabolous insect that plays a significant economic role in the production of silk. The trimolter silkworms have garnered significant interest among sericulturists owing to their superior filament fineness, shorter larval duration, and reduced labor inputs. These traits render the trimolter silkworms suitable for specialized raw silk manufacturing. However, some individuals from trimolter strains may undergo an additional molt, resulting in tetramolter silkworms. The cause of this change is unclear and is the focus of this study. The trimolter silkworm variety ‘Guangri 3’, characterized by stable molting traits, is a bivoltine strain, though occasional individuals may exhibit increased molting number. Thus, the research subjects were the ‘Guangri 3’ trimolter silkworms raised at 25°C in spring (Group A: trimolter individuals as TA and tetramolter variants with increased moltinism as FA) and at 30°C in autumn (Group B: the trimolter individuals as TB and tetramolter variants with increased moltinism as FB). Statistical analysis revealed that the incidence rates of FA and FB were 1.10% and 16.10%, respectively. Subsequently, RNA-seq analysis was conducted on distinct groups. The results showed that: In group A (FA vs TA), 1,044 genes were upregulated and 846 were downregulated. In the group B (FB vs TB), 808 genes were upregulated and 707 were downregulated. GO and KEGG enrichmentanalyses of the differentially expressed genes (DEGs) in both FA vs TA and FB vs TB comparisons revealed pathways associated with insect molting, such as chitin catabolism, which encompassed key gene families including CYP, CPR, and Rp. Furthermore, PPI network analysis of the FB vs TB group identified hub genes (e.g., Hsp83), whose potential role in molting alteration under high temperature warrants further investigation.

ORGANISM(S): Bombyx mori

PROVIDER: GSE317076 | GEO | 2026/07/01

REPOSITORIES: GEO

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Project description:Single-base resolution DNA methylomes have been accomplished for both Arabidopsis and human cells which have high genome methylation levels by Illumina ultra-high-throughput bisulfite sequencing technology (MethylC-Seq). Here by combining MethylC-Seq and biological replicate strategies we generated single-base resolution methylome for the silkworm which has low genome methylation levels like other insects. Our conservative estimation showed that methylcytosines (mCs) accout for about 0.11% of genomic cytosines, exclusively in CG context. The CG methylation is significantly enriched in gene bodies and positively correlated with gene expression levels, suggesting its positive role in gene transcription in silkworms. However, the well-documented functions of methylation on promoters and rDNAs in plants and mammals do not seem to have effects in insects. Methylated genes are enriched in functions involved in cellular metabolism and biosynthesis. Small RNA (smRNA) loci are also significantly enriched in gene bodies, and moreover, the smRNA loci and the predicted target sites of microRNA have high level of CG methylation, indicating functional involvement of smRNAs in the genic methylation This first methylome for silkworms provides a foundation for further studies on the epigenetic gene regulation of silkworms’ or even insects’ gene methylation. Each silk gland of 5th instar larvae of two individuals (called Biological Replicate 1 and 2, respectively) of the silkworm (Bombyx mori) strain Dazao was ground into powder in liquid nitrogen. Half of the powder from each silk gland was used to extract total DNAs using DNeasy Blood & Tissue Kit (Qiagen) and another half was used to extract total RNAs using RNeasy Mini Kit (Qiagen). We sequenced bisulfite-treated total DNA extracted from the silk glands of the two individuals, using Illumina Ultra-High-Throughput Sequencing, generating the Single-Base Resolution Methylomes. To reveal functional consequences of gene body methylation, we generated expression profiles for the two individuals’ silk glands using Digital Gene Expression tag profiling (DGE) technology, which combines classic SAGE (Serial Analysis of Gene Expression) and Illumina ultra-high-throughput sequencing technology.

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Transcriptome analysis of molting variation in dominant trimolter silkworms, Bombyx mori

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