Expression of ecdysone receptor is unaffected by pupal diapause in the flesh fly, Sarcophaga crassipalpis, while its dimerization partner, USP, is downregulated

We have developed partial clones of ecdysone receptor (EcR) and ultraspiracle (USP) from the flesh fly, Sarcophaga crassipalpis, using rt-PCR. These clones were used to assess the expression of both genes during pupal diapause. Transcripts of EcR remain present throughout diapause, with levels increasing upon termination. Expression is not uniform during diapause, but shows considerable individual variation. Conversely, transcripts of USP gradually decrease when diapause is initiated and are undetectable 20 days after the onset of diapause. Late in diapause USP transcripts are again evident, and at diapause termination USP is quickly upregulated. These results suggest the possibility that upregulation of USP is involved in preparing the flesh fly to terminate diapause.