# Detoxification Metabolic Adaptation of Bombyx mori to Artificial Diet and Functional Study of Key Detoxification Gene BmGSTd2

## TL;DR

This study explores how silkworms adapt to artificial diets by identifying a key detoxification gene, GSTd2, which helps them tolerate harmful plant compounds.

## Contribution

The study identifies GSTd2 as a critical gene enabling silkworms to adapt to artificial diets through enhanced detoxification.

## Key findings

- Dietary shift to artificial feed enriches detoxification pathways and accumulates flavonoids in silkworm detox organs.
- Overexpression of GSTd2 in BmE cells increases tolerance to harmful flavonoids like genistein and daidzin.
- Silkworms with GSTd2 overexpression show improved adaptability to artificial diets.

## Abstract

This study aims to explore the adaptive mechanisms underlying the silkworm’s (Bombyx mori) transition from a natural mulberry leaf diet to an artificial diet. The results showed that dietary shift induced the accumulation of specific plant-derived compounds (e.g., flavonoids) in key detoxification organs of silkworms—including the fat body, midgut, and Malpighian tubules—while activating multiple detoxification pathways within these tissues. Experimental analysis showed that these compounds, particularly the flavonoids genistein and daidzin, exhibit cytotoxicity and can trigger the transcriptional activation of detoxification-related genes. Among these genes, GSTd2 emerged as a critical mediator: elevated expression of GSTd2 in BmE cells significantly enhanced cellular tolerance to these harmful flavonoids. Furthermore, silkworms with systemic overexpression of GSTd2 displayed markedly improved adaptability to the artificial diet. Collectively, this study elucidates the molecular basis of dietary adaptation in insects, providing valuable insights for optimizing artificial feed formulations and enhancing the efficiency of silkworm rearing.

The exceptional adaptability of insects to diverse food sources is central to their survival and evolutionary success. However, the molecular mechanisms underlying this rapid adaptation remain largely uncharacterized. In this study, adaptive phenotypic, transcriptomic, and metabolomic differences in silkworms fed mulberry leaves versus artificial diets were investigated. The results showed that dietary changes induced enrichment of multiple detoxification pathways in the fat body, midgut, and Malpighian tubules, accompanied by significant accumulation of secondary metabolites and xenobiotics such as flavonoids, terpenoids and saponins in these tissues. Stimulation experiments with nine upregulated metabolites in silkworm BmE cells revealed that most metabolites inhibited cell viability and induced detoxification genes such as GST, UGT and CYP upregulated, with flavonoids like genistein and daidzin exhibiting obvious inductive effects. Among the upregulated genes, GSTd2 frequently responded and was significantly upregulated in artificial diet-fed silkworms. Notably, overexpressing GSTd2 in BmE cells enhanced cell tolerance to genistein and daidzin. Furthermore, silkworms overexpressing GSTd2 showed higher flavonoid tolerance and better adaptability to artificial diets. In conclusion, this study provides valuable genetic targets for improving silkworm rearing efficiency on artificial diets, providing reference to optimize feed formulations and theoretical basis for understanding metabolic adaptation mechanisms to artificial diets in silkworms.