Hyperthermia-induced transcriptome remodeling impairs embryo viability in Bombyx mori

Acid treatment at an appropriate temperature can simultaneously prevent egg diapause and microsporidian transmission in sericulture. However, the transcriptional features associated with excessive thermal stress in the eggs of Bombyx mori remain unclear, which limits further studies on this dual-purpose treatment. Here, we comparatively analyzed the effects of two temperatures and proposed that 47.5°C (T1) and 48.5°C (T2) represent threshold and extreme temperatures for diapause termination, respectively. Furthermore, the full-length (FL) transcriptome was used to produce 49,444 high-confidence transcripts, including 1,571 long non-coding RNAs (lncRNAs). Comprehensive transcriptome analysis showed that 274 downregulated and 255 upregulated genes were identified in the T2 treatment relative to the T1 counterpart, including 82 differentially expressed transcription factor genes. Noticeably, 23 downregulated Homeobox genes and 5 upregulated bHLH genes were detected. Six lncRNAs were differentially expressed between the T2 and T1 treatments. Functional enrichment analysis showed that the downregulated genes were significantly enriched in gene expression regulation and carbohydrate and important amino acid metabolism. However, upregulated genes were mainly involved in the pathways closely related to heat shock proteins (HSPs), indicating their conserved functions in stress responses and molecular chaperones. This study provides comprehensive insights on the genes expressed in B. mori eggs exposed to extreme thermal stress and provides a valuable resource for in-depth investigations of the response of embryos to excessive thermal stress and the balance between effective pathogen control and maintenance of embryo viability in silkworm.