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 different hormone nuclear receptors were isolated from Tenebrio molitor mRNAs. The sequence identity of three of them with known Drosophila nuclear receptors strongly suggests that they are the Tenebrio orthologs of seven‐up , DHR3 and β‐FTZ‐F1 , and thus named Tmsvp , TmHR3 and TmFTZ‐F1 . The full‐length sequences of the other two were established. TmHR78 is either a new receptor of the DHR78 family or the same gene which has evolved rapidly, particularly 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 affinity. The periods of expression of the corresponding transcripts in epidermal cells during Tenebrio metamorphosis were analyzed as a function of 20‐hydroxyecdysone titers measured in the hemolymph of the animals taken for RNA extraction. Comparison of the expression profiles of these nuclear receptors with those observed during Drosophila metamorphosis revealed similar temporal correlations as a function of ecdysteroid variations, which further supported the sequence identity data for Tm SVP, Tm HR3, Tm FTZ‐F1 and Tm HR78.