Comparative analysis of heat shock promoters efficiency in two diptera species

Heat shock proteins (Hsp) provide cellular and whole body adaptation of animals to various adverse environmental conditions. Hsp70 is apparently the major player underlying biological adaptation in all organisms studied so far. In all animals the regulatory regions of studied heat shock genes include several conservative promoter elements HSEs (heat shock elements) that are necessary for binding of heat shock transcription factor (HSF). The promoter regions of hsp70 genes are extremely conserved and, hence, it was generally accepted that they are universal and can operate in species belonging to different phyla. In the present work we performed the comparative analysis which revealed characteristic differences in the hsp 70 promoters of two Diptera species: Drosophila melanogaster and highly thermotolerance soldier fly Stratiomys singularior. We measured promoters activity in D. melanogaster cell culture exploring in vitro luciferase reporter assay. The analysis demonstrated significantly higher strength ofD. melanogaster promoters in spite of the fact that comparable numbers of HSEs are present in both species. These drastic differences in the promoter strength are probably due to absence of GAF-binding sites, which are necessary for efficient functioning of D. melanogaster hsp70 promoters. In contrast, comparison of hsp83 promoters isolated from these two species does not show significant differences. Our results demonstrate existence of different evolutionary trends in the regulation of the hsp70 expression even within the same order (Diptera).