Aldehyde reductase via sorbitol synthesis alters diapause incidence in silkworm eggs

The accumulation of sorbitol within silkworm eggs is a critical factor driving the onset of diapause. Sorbitol can be synthesized via glucose conversion by polyol dehydrogenase I. However, the gene encoding this enzyme remains unidentified. This study investigates the Bombyx mori aldehyde reductase gene (BmAR), a member of B subfamily within the aldo-keto reductases superfamily, which is highly expressed in the ovaries of mother larvae and moths and in eggs destined for diapause. Using overexpression and RNA interference techniques, we demonstrated that BmAR likely modulates sorbitol levels during diapause initiation. CRISPR-Cas9-mediated gene knockout further confirmed its functional role, showing that disruption of BmAR altered the proportion of diapause eggs and modified the diapause phenotype. Notably, BmAR expression also differs significantly among silkworm varieties with different types of voltinism. These results suggest that BmAR may be responsible for conversion of glucose to sorbitol during silkworm egg diapause. This discovery enriches the molecular regulatory network of carbohydrate metabolism during diapause entry in silkworms and provides valuable insights into the mechanisms underlying insect diapause.