Accumulation of Hsp70 mRNA under environmental stresses in diapausing and nondiapausing adults of Drosophila triauraria.

Drosophila triauraria entered reproductive diapause in response to short daylengths and acquired tolerance to heat, cold and desiccation. In this species, the heat-shock response (accumulation of Hsp70 mRNA in response to heat) occurred at 27-41 degrees C, and the level of Hsp70 mRNA did not differ between diapausing and nondiapausing individuals. Hsp70 mRNA was also induced by exposure to -4 or -8 degrees C. However, it was scarcely detected just after the exposure to cold, but accumulated when flies were maintained at normal temperature following the exposure to cold. The level of Hsp70 mRNA was lower in diapausing individuals than in nondiapausing ones when exposed to -4 degrees C, but was not different between them when exposed to -8 degrees C. This species did not synthesize Hsp70 mRNA under desiccation stress irrespective of the diapause state. These results suggest that diapausing individuals of this species acquired tolerance to heat, cold and desiccation independent of the transcriptional regulation of the hsp70 gene