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Functional analysis of HSP complex expression in response to cold in \kur{Drosophila melanogaster}
ŠTĚTINA, Tomáš
The constitutively obsereved up-regulation of Hsp70 expression often led to premature conclusions about its critical role as a repair mechanism of cold injury that is, besides, expressed by protein misfolding/denaturation. In this study, we analyze the cold tolerance and the expression of 24 different mRNA transcripts of Hsp complex and other genes, that are associated with the repair of injury caused by cold. We use two strains of D. melanogaster: the wild type and the mutant type Hsp70- null, that lacks all 6 copies of the gene hsp70. We found out, that the larvae of two strains do not differ in their patterns of target genes expression during long term acclimation nor during recovery from chronic cold exposure and acute cold shock, therefore there is no transcriptional compensation of any other Hsp gene for the missing hsp70 in Hsp70- strain. The cold tolerance of Hsp70- strain larvae was impaired only, when they were exposed to strong acute cold shock by temperatures below -8°C. No difference in cold tolerance was observed, when the larvae were exposed to chronic cold exposure in 0°C or to mild acute cold shock by temperatures up to -4°C. Based on our results we assess, that the cold injury caused by strong acute cold schock is of another nature than caused by mild cold conditions and only in the first case Hsp70 expression is critical for the repair of cold injury in Drosophila melanogaster larvae.
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