# Pyriproxyfen Disrupts Chitin and Trehalose Metabolism in the Silkworm Bombyx mori

## TL;DR

This study shows how the pesticide pyriproxyfen harms silkworms by disrupting their chitin and trehalose metabolism, leading to developmental issues and offering insights into safer pest control.

## Contribution

The study reveals tissue-specific and spatiotemporal gene expression changes in silkworms due to pyriproxyfen exposure, linking them to disrupted chitin and trehalose metabolism.

## Key findings

- Pyriproxyfen exposure causes a biphasic 'suppression–compensation' trend in chitin- and trehalose-related gene expression.
- Tissue-specific responses were observed, with ChsA continuously suppressed in the middle silk gland and abnormally upregulated in the posterior silk gland.
- Trehalose metabolism genes paralleled chitin gene fluctuations, indicating systemic metabolic reprogramming.

## Abstract

Pyriproxyfen is a pesticide widely used to control agricultural pests, but it also poses risks to beneficial non-target insects like the silkworm. While this chemical is known to damage silk production and prevent silkworms from maturing, the specific biological reasons for this toxicity remain unclear. This study investigated the transcriptional basis of how pyriproxyfen exposure is linked to altered metabolism of two vital substances: chitin, the material that forms the insect’s hard outer skeleton and internal structures, and trehalose, the primary blood sugar used as energy to build chitin. By analyzing gene activity in silkworms exposed to the pesticide, this research aimed to characterize the transcriptional response associated with pyriproxyfen toxicity. The exposure was associated with a chaotic fluctuation in gene levels, coinciding with the suppression of biological functions and triggering an ineffective repair attempt. These transcriptional changes are consistent with the disrupted silk gland development and larval–pupal metamorphosis observed previously. These findings are crucial for understanding the hidden dangers of pesticide residues in the environment. Furthermore, this research provides a scientific basis for assessing environmental risks and developing safer, more selective pest control strategies. The data also suggest a potential compensatory metabolic response under sustained insecticide exposure that protects economically important insects.

Pyriproxyfen, a juvenile hormone analog insecticide, poses severe risks to non-target silkworms (Bombyx mori), as evidenced by disrupted metamorphosis—a process strictly dependent on chitin synthesis and its precursor trehalose. However, the specific molecular interference of pyriproxyfen in these metabolic pathways remains unclear. This study investigated the transcriptional response of silkworm midguts to pyriproxyfen using RNA-Seq and validated spatiotemporal gene expression via qRT-PCR. By integrating transcriptomic data with long-term spatiotemporal profiling, we revealed novel tissue-specific expression dynamics. RNA-Seq identified 2059 differentially expressed genes, primarily enriched in metabolic pathways. Spatiotemporal analysis revealed that most chitin- and trehalose-related genes generally exhibited a biphasic “suppression–compensation” trend (initial downregulation followed by upregulation). Notably, tissue-specific responses were evident, with ChsA being continuously suppressed in the middle silk gland, which may be associated with impaired sericin secretion, while showing abnormal upregulation in the posterior silk gland. Additionally, trehalose metabolism genes (Treh and Tret) paralleled the fluctuation of chitin genes, indicating systemic metabolic reprogramming. These results suggest that the toxicity of pyriproxyfen is associated with a decoupling of trehalose metabolism from chitin synthesis and the induction of tissue-specific metabolic disorders. The tissue-specific, long-term spatiotemporal profiling of chitin and trehalose genes presented in this study fills a critical knowledge gap. This study characterizes the transcriptional profile associated with pyriproxyfen toxicity and provides a robust molecular reference for assessing its environmental risks to beneficial insects.