20-Hydroxyecdysone Modulates Bmp53-Mediated Apoptosis Regulation by Suppressing Mdm2-like-Dependent Ubiquitination in Silkworm, Bombyx mori.

In the silkworm, 20-hydroxyecdysone (20E) induces apoptosis and autophagy, driving larval organ degeneration and remodeling. This mechanism may be a potential target for eco-friendly strategy for insect pests. However, a major challenge in harnessing this approach lies in the insufficient understanding of 20E's regulatory process in such a cell death mechanism. Our previous research has identified Bmp53 as a crucial gene in promoting the development of Bombyx mori during the pupal stage by inducing apoptosis, and has predicted the potential apoptotic regulatory network of Bmp53, wherein Mdm2-like ubiquitinating structural protein serves as a key component of this network. This study demonstrates that Mdm2-like acts as a ubiquitination regulatory protein, controlling its apoptosis-inducing activity via interaction with Bmp53. Moreover, co-expression of Mdm2-like and Bmp53 indirectly affects gene expression in the 20E-mediated apoptosis pathway. Further investigation revealed that Mdm2-like suppresses 20E-induced apoptosis by downregulating Bmp53 expression. This study reveals that the ubiquitination-mediated Mdm2-like/Bmp53 apoptosis pathway is a novel mechanism regulating silkworm apoptosis, with 20E playing a crucial role in this process. These findings enhance our understanding of the genetic mechanisms underlying tissue degradation during the metamorphic stage of the Bombyx mori. Additionally, these insights provide a theoretical reference for the development of environmentally friendly, hormone-based control strategies targeting protein modification as a means of managing lepidopteran pests.