The impact of the <i>BmSur8</i> gene, encoding a scaffold protein, on cocoon silk yield in <i>Bombyx mori</i>

Cocoon silk quality is a critical determinant of the economic value in the sericulture industry for Bombyx mori L. (Lepidoptera: Bombycidae). Sur8 functions as a positive regulator of the RAS-MAPK signaling cascade, which plays an essential role in regulating cocoon silk production in Bombyx mori. However, the specific functions of BmSur8 in silkworms have not been fully elucidated. In this study, we demonstrate that BmSur8 is a highly conserved gene expressed across all life stages and various tissues at the third day of the fifth instar larvae (L5D3) stage in Bombyx mori. Knockout of the BmSur8 gene results in a 15.2% reduction in silk yield in females and a 13.4% reduction in males, with the cocoon layer rate in females decreasing by 3.8%. Through transcriptomic analysis of posterior silk glands (PSGs) at L5D3 stage from ΔBmSur8 mutants and Nistari controls, as well as mass spectrometry analysis of BmSur8-interacting proteins in BmN cells, we find that BmSur8 potentially interacts with BmEtfb and regulates the expression of BmCDA and BmjunD, thereby participating in material and energy metabolism. This study provides a comprehensive analysis of the function of BmSur8 in metabolic pathways and offers theoretical insights and experimental data for researching silkworm cocoon silk quality and yield, as well as for breed selection and breeding.