Molecular cloning and expression of Tenebrio molitor ultraspiracle during metamorphosis and in vivo induction of its phosphorylation by 20-hydroxyecdysone

Using a RT-PCR approach, the Tenebrio molitor homologue of Drosophila Ultra spiracle (TmUSP) was characterized. Its DNA binding domain shows a degree o f identity with those of the other insect USPs. However, the ligand binding domain is closer to those of retinoid X receptors. Using an antibody raise d against DmUSP, Western blot analysis of proteins from epidermis and other tissues revealed five immunoreactive bands, corresponding to different pho sphorylated forms of a unique polypeptide, as shown by lambda-phosphatase t reatment. The nuclear form of TmUSP seems unphosphorylated. An in vivo 20-h ydroxyecdysone treatment increases considerably and rapidly the phosphoryla ted forms of TmUSP. This post-translational modification may play a role in the 20-hydroxyecdysone response.