UDP-glycosyltransferase-mediated adaptation to mulberry flavonoids enhances silkworm detoxification and antioxidant capacity

• Dietary flavonoid intake, mainly quercetin and kaempferol, upregulate detoxification enzyme activities. • Flavonoids and UGT inhibitors significantly impair the growth and development of silkworm. • BmUGTs exhibit ubiquitous expression across diverse widely expressed in multiple tissues and developmental stages. • BmUGT40K1 is a critical enzyme for metabolizing diverse mulberry leaf flavonoids. • BmUGT40K1 augments both detoxification capacity and antioxidant activity in silkworm. Uridine diphosphate (UDP) glycosyltransferases (UGTs) are a major class of detoxifying enzymes that metabolize xenobiotics through glycosylation. Although UGTs are widely implicated in insect resistance to plant secondary metabolites (PSMs), their functions in adapting to host plant flavonoids remain unclear. Revealing the function of UGT in the adaptation of the silkworm to mulberry flavonoids. In this study, we investigated the function of Bombyx mori UGT40K1 (BmUGT40K1) using a multi-methodological approach that integrated in vitro enzyme activity detected by HPLC-MS/MS, transgenic overexpression, and CRISPR/Cas9-mediated knockout. The results showed that flavonoid treatment on silkworm induces physiological and developmental impairments similar to those caused by UGT inhibitors. In vitro enzyme assays confirmed that BmUGT40K1, which is predominantly expressed in detoxification organs such as midgut during the larval feeding stage, is a crucial enzyme capable of metabolizing these flavonoids. Functional studies further revealed that BmUGT40K1 not only directly facilitates flavonoid detoxification but also modulates the activities of other detoxification enzymes and oxidoreductases. BmUGT40K1 plays a central role in flavonoid resistance and likely serves as an important mediator of antioxidant capacity in silkworm. These findings deepen our fundamental understanding of insect-plant coevolution and adaptive responses to phytochemicals.