Hypoxanthine accumulation caused by mutations of Bombyx mori xanthine dehydrogenase triggers female sterility.

Insect reproductive capacity is a key determinant of population fitness, though its regulatory mechanisms remain limited. Here, we identified an op50 silkworm mutant (derived from p50 strain) exhibiting female-specific reproductive defects, which provided an important model for studying insect reproductive regulation mechanism. We found that Bombyx mori xanthine dehydrogenase 1 (BmXDH1) in op50 contained a single-base insertion causing premature termination, deleting 154 C-terminal amino acids and losing catalytic activity. ΔBmXDH1 mutants recapitulated the op50 phenotype with 50 % reduced oviposition and 90 % lower hatchability, attributed to severe structural impairments of the eggshell surface and egg surface pore. In addition, female reproductive defects initiated at the pupal stage, characterized by oviduct malformation and impaired oviposition. This phenotype was associated with excessive accumulation of hypoxanthine, leading to ovarian and embryonic developmental disruption, including extracellular matrix remodeling, cellular signaling pathways, and oxidative stress regulation. The results uncovered how BmXDH1 regulates hypoxanthine metabolism to control silkworm reproduction, advancing understanding of insect reproductive networks and providing targets for pest control/economic insect breeding.