The life cycle of holometabolous insects involves different stages and cathepsin plays an important role in insect metamorphosis. In the present study, we investigated the function of Bombyx mori cathepsin-L (Bm-CatL) during metamorphosis and analyzed their role in programmed cell death (PCD) of the fat body. The results showed that knockdown of Bm-CatL by RNA interference led to abnormal pupation and a delay in fat body degradation during metamorphosis. Furthermore, PCD inhibition was observed in the fat body after downregulation of Bm-CatL. To confirm this finding, PCD was induced in Bombyx mori embryonic (BmE) cells by ultraviolet ray irradiation. We found that the PCD of BmE cells was weakened after knocking down Bm-CatL. Moreover, overexpression of Bm-CatL in cells promoted PCD. Overall, our results showed that Bm-CatL is involved in the degradation of internal tissues and promotes the PCD of cells involved in the pupation of silkworms. Thus, this study provides us with a better understanding for function of cathepsin-L during metamorphosis.

整体代谢昆虫的生命周期涉及不同阶段，而组织蛋白酶在昆虫变态中起着重要作用。在本研究中，我们调查了家蚕组织蛋白酶L（Bm-CatL）在变态过程中的功能，并分析了它们在脂肪体程序性细胞死亡（PCD）中的作用。结果表明，RNA干扰敲除Bm-CatL会导致化脓和变态过程中脂肪体降解的延迟。此外，在Bm-CatL下调后，在脂肪体内观察到PCD抑制。为了证实这一发现，通过紫外线照射在家蚕胚胎（BmE）细胞中诱导了PCD。我们发现敲低Bm-CatL后BmE细胞的PCD减弱。此外，Bm-CatL在细胞中的过表达促进了PCD。总体，我们的结果表明，Bm-CatL参与内部组织的降解，并促进参与家蚕化up的细胞的PCD。因此，这项研究使我们对组织蛋白酶-L在变态过程中的功能有了更好的了解。