Cloning and characterization of new orphan nuclear receptors and their developmental profiles during Tenebrio metamorphosis

Five PCR fragments corresponding to a part of the DNA-binding domain of dif ferent hormone nuclear receptors were isolated from Tenebrio molitor mRNAs. The sequence identity of three of them with known Drosophila nuclear recep tors strongly suggests that they are the Tenebrio orthologs of seven-up, DH R3 and beta-FTZ-F1, and thus named Tmsvp, TmHR3 and TmFTZ-F1. The full-leng th sequences of the other two were established. TmHR78 is either a new rece ptor of the DHR78 family or the same gene which has evolved rapidly, partic ularly in the E domain. TmGRF belongs to the GCNF1 family and its in vitro translated product binds to the extended half site TCAAGGTCA with high affi nity. The periods of expression of the corresponding transcripts in epiderm al cells during Tenebrio metamorphosis were analyzed as a function of 20-hy droxyecdysone titers measured in the hemolymph of the animals taken for RNA extraction. Comparison of the expression profiles of these nuclear recepto rs with those observed during Drosophila metamorphosis revealed similar tem poral correlations as a function of ecdysteroid variations, which further s upported the sequence identity data for TmSVP, TmHR3, TmFTZ-F1 and TmHR78.