UP-REGULATION OF A 23 KDA SMALL HEAT-SHOCK-PROTEIN TRANSCRIPT DURING PUPAL DIAPAUSE IN THE FLESH FLY, SARCOPHAGA-CRASSIPALPIS

A diapause upregulated cDNA clone was isolated from a cDNA library gen erated from brain mRNA of diapausing Sarcophaga crassipalpis pupae. Th e clone hybridized to a 1600 bp transcript on a northern blot. The ins ert is 823 bp in length, has a tentative open reading frame of 615 bp, and codes for a 23 kDa protein. The clone has a high level of identit y at the amino acid level with the four small heat shock proteins of D rosophila melanogaster. Northern analysis revealed no detectable expre ssion of the transcript in diapause- or nondiapause-programmed wanderi ng larvae. and only trace expression in nondiapausing pupae. But, the transcript was highly expressed beginning at the onset of diapause and continuing throughout diapause. Expression promptly decreased when di apause was terminated. In nondiapausing individuals the transcript was highly expressed in response to cold shock or heat shock, but tempera ture stress did not cause greater expression in diapausing pupae. The results imply that expression of this small heat shock protein, a resp onse elicited by temperature stress ill nondiapausing individuals, is a normal component of the diapause syndrome. The upregulation of this gene during diapause suggests that it plays an essential role during t his overwintering developmental arrest. (C) 1998 Elsevier Science Ltd. All rights reserved.