# Histopathological and Transcriptional Changes in Silkworm Larval Gonads in Response to Chlorfenapyr Exposure

## TL;DR

This study explores how the insecticide chlorfenapyr affects the reproductive development of silkworms by examining changes in their gonads and gene activity.

## Contribution

The study provides new insights into the molecular mechanisms by which chlorfenapyr impacts silkworm reproductive development.

## Key findings

- Chlorfenapyr exposure caused delayed gonadal development and reduced oogonia and spermatocytes in silkworms.
- Transcriptome analysis revealed key genes and pathways involved in detoxification and hormonal regulation in response to chlorfenapyr.
- Protein–protein interaction networks identified hub genes like EcR and Kr-h1 linked to reproductive development.

## Abstract

Bombyx mori is not only an important agricultural economic insect but also a representative lepidopteran model insect. Due to long-term indoor breeding and domestication, silkworms are highly sensitive to many chemical pesticides, and they serve as a research model for evaluating the reproductive development of pesticides on organisms. This study investigates the histopathology and transcriptome of gonads (ovaries and testes) of silkworms following exposure to chlorfenapyr. After exposure for 72 h and 96 h, chlorfenapyr caused abnormal development in larval silkworm gonads. At a transcriptome level, DEGs were primarily associated with drug metabolism—cytochrome P450, drug metabolism—other enzymes, and insect hormone biosynthesis. A regulatory network is constructed to identify key responsive proteins. These findings provide new insights into the molecular mechanism by which chlorfenapyr affects reproductive development.

Chlorfenapyr is a widely used insecticide known to harm non-target insects, but its effects on reproductive development in the silkworm (Bombyx mori L.) remain incompletely understood. In this study, we investigated the histopathological and transcriptional changes in the gonads (ovaries and testes) of newly molted fifth-instar silkworm larvae exposed to chlorfenapyr. Histopathological analysis revealed delayed gonadal development, a reduction in oogonia and oocytes in the ovaries, and decreased numbers of spermatocytes in the testes. Transcriptome analysis identified significant differentially expressed genes (DEGs), mainly enriched in pathways such as “Drug metabolism—cytochrome P450”, “Insect hormone biosynthesis”, and “Ribosome”. Key up-regulated genes included members of the cytochrome P450 family (CYP6B5, CYP9f2, CYP6B6), glutathione S-transferases (GSTT1, GST1), and juvenile hormone-related enzymes (JHAMT, JHEH), indicating active detoxification and hormonal regulation responses. Several transcription factor families, particularly C2H2, HB-other, and TRAF, exhibited altered expression, suggesting roles in stress adaptation. Protein–protein interaction (PPI) network analysis identified hub genes such as EcR, Kr-h1, and various ribosomal proteins, highlighting their potential involvement in reproductive development. Quantitative PCR (qPCR) validated the transcriptomic data, confirming the reliability of the results. Overall, these findings enhance our understanding of chlorfenapyr’s impact on silkworm reproductive development and the underlying molecular mechanisms, providing valuable insights for sustainable pest management and ecological risk assessment of insecticides.