Transcriptome and detoxification enzyme–related gene analysis of the Cydia pomonella response to walnut husks

Walnut husks, as an agricultural by-product, have various applications in industries such as food, agriculture, and medicine. However, few studies have examined the effects of walnut husks on the growth, development, and RNA levels of Cydia pomonella larvae. This study preliminarily elucidated the detoxification mechanism of C. pomonella in response to walnut husks using transcriptome (total RNA sequencing) analysis and enzyme activity assays. Feeding trials demonstrated that walnut husks significantly reduced larval body length, head capsule width, body weight, and survival rate, while prolonging developmental duration and increasing the female ratio. RNA-seq analysis identified 2918 differentially expressed genes (DEGs) out of a total of 23,426 genes, including 1546 upregulated and 1372 downregulated genes relative to the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that these differentially expressed genes were significantly enriched in oxidoreductase activity, metabolic processes, xenobiotic and drug metabolism by cytochrome P450, pentose and glucuronate interconversion, oxidative phosphorylation, and ascorbate and aldarate metabolism. Among these, 34 detoxification-related DEGs were identified, comprising 29 cytochrome P450 genes and 5 glutathione peroxidase genes. The reliability of the transcriptome data was validated by qRT-PCR, and at the protein level by the measurement of antioxidant (CAT, POD, SOD) and detoxification (GST, CarE, MFO) enzyme activity. The results indicated that walnut husks trigger a stress response in C. pomonella larvae, while genes related to detoxification await further investigation. The findings of this study not only provide a solid foundation for elucidating the detoxification mechanisms of C. pomonella in response to walnut husk components, but also lay a theoretical basis for future strategies involving RNA interference and molecular target screening based on key detoxification genes, offering new insights into the development of efficient, safe, and environmentally friendly precision pest control technologies.