Heat-shock protein 90 is down-regulated during pupal diapause in the fleshfly, Sarcophaga crassipalpis, but remains responsive to thermal stress

Heat-shock protein 23 (hsp23) and hsp70 are both known to be strongly up-re gulated during pupal diapause in the flesh fly Sarcophaga crassipalpis, Thi s prompted us to investigate whether hsp90 was also up-regulated during dia pause. To test this possibility, we developed a partial clone of a hsp90 fa mily member for use as a probe in Northern blot hybridization. Both high an d low temperature exposure up-regulated hsp90 transcripts in nondiapausing individuals. In contrast to hsp23 and hsp70, hsp90 was down-regulated follo wing entry into diapause, and returned to prediapause levels after diapause termination. The response of hsp90 to heat shock and cold shock remained i ntact during diapause: both shocks evoked elevated expression. The results indicate differential regulation of hsps during diapause and in response to thermal injury inflicted on diapausing pupae.