Dosage-dependent regulation of embryonic diapause by sorbitol dehydrogenase in the silkworm, Bombyx mori

Insects have evolved diapause to cope with harsh environmental conditions, during which their metabolism undergoes significant remodeling. The silkworm, Bombyx mori, enters diapause in the early embryonic stage, a process critically regulated by the sorbitol metabolism pathway and its key enzyme, sorbitol dehydrogenase (SDH). Nevertheless, the precise involvement of SDH in the diapause regulation of the silkworm remains to be fully understood. In this study, we identified that BmSdh2 is highly expressed in diapause-destined silkworm embryos through RNA-seq analysis. Genetic manipulation of BmSdh2 expression significantly influenced diapause progression: complete homozygous knockout of BmSdh2 led to diapause termination, whereas partial loss-of-function mutations maintained the wild-type diapause phenotype. Furthermore, integrative LC-MS/MS, metabolomic, and lipidomic analyses demonstrated that BmSdh2 dosage critically modulates diapause maintenance. These findings highlight BmSdh2 as a novel and potentially central molecular regulator in the silkworm diapause pathway.