Diapause Contents

Downregulation of ultraspiracle but not ecdysone receptor during pupal diapause in Sarcophaga crassipalpis

J. P. Rinehart, and T. L. Craig, D. L. Denlinger

Dept. of Entomology, Ohio State Univ., 1735 Neil Ave., Columbus, OH 43210-1220, USA

The establishment and maintenance of diapause is under neuroendocrine control. In species that undergo pupal diapause, such as the flesh fly Sarcophaga crassipalpis, this control is characterized by the lack of ecdysteroids. While the role of ecdysteroids during pupal diapause is well defined, the expression of ecdysteroid receptors remains unclear. To resolve this issue, we first used rt-PCR to develop partial clones of ecdysone receptor (EcR) and its dimerization partner ultraspiracle (USP) from S. crassipalpis. These clones were then used as probes for northern blotting and in situ hybridization to analyze gene expression during diapause and diapause termination. Northern blot hybridization revealed that transcripts of EcR remain present throughout diapause, with levels further 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. Data from in situ hybridization have defined specific expression patterns in the brain throughout diapause and at the onset of adult development. The implications of these results will be discussed, including the possibility that the late diapause upregulation of USP suggests its involvement in preparation for diapause termination.

Index terms: Sarcophaga crassipalpis, in situ, diapause, ecdysone receptor, ultraspiracle

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