Cloning and Characterization of the Caspase Family Member BmDronc from Bombyx mori (Lepidoptera: Bombycidae) Embryo Cells

Abstract Caspases are a family of cysteinyl aspartate proteinases known for their essential roles in the regulation of apoptosis. To date, ≈20 caspases have been identified, although few have been cloned and characterized in Bombyx mori (L.). Two caspase-9 variants from the B. mori embryo cell line (BmE), designated BmDroncL and BmDroncS, were cloned. BmDroncL has three classic domains: a caspase recruitment domain and large and small subunits, and is a homologue of Drosophila Dronc, human caspase-9, Aedes Dronc, and fish caspase-9, whereas BmDroncS lacks the large subunit. Instantaneous expression of BmDroncL caused typical apoptosis in Sf-9 cells. Moreover, BmDronc gene expression increased markedly during the silkworm metamorphosis at the larva-pupa and pupa-moth stages, which suggested that BmDronc plays a crucial role during B. mori metamorphosis.