Expression analysis and functional identification of several genes related to diapause in Bombyx mori

Diapause is an important characteristic of insects used to adapt to extreme changes in environmental conditions. Embryonic diapause of the bivoltine silkworm (Bombyx mori) is determined by environmental conditions experienced by the mother while in the embryo stage. If they are incubated at 25°C with natural light, their progenies will be diapause-destined. If they are incubated at 17°C in darkness, their progenies will be non-diapause-destined. The molecular mechanism of diapause remains unknown. In the present study, we analyzed two downregulated genes (BGIBMGA003835, BGIBMGA012335) and two upregulated genes (BGIBMG012996, BGIBMG002426) related to carbohydrate metabolism, verified differentially expressed in ovaries and heads of 1-day-old fifth-instar larvae to 6-day pupae by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). In line with published data, the expression level of these genes in larvae were generally lower than in pupae. We further analyzed the expression levels of the four genes in BmN cells that had been treated with various concentrations of diapause hormone (DH). It demonstrated that the expression of these genes was affected by DH. Knockdown of the selected genes in non-diapause-destined female pupae changed the fate of the progeny from non-diapause- to daipause-destined, as seen by the appearance of diapause eggs. Our study provides insight into the molecular mechanism of diapause in B. mori.