Molecular mechanisms underlying thermal adaptation of xeric animals.

For many years,we and our collaborators have investigated the adaptive role of heat shock proteins in different animals,including the representatives of homothermic and poikilothermic species that inhabit regions with contrasting thermal conditions. Adaptive evolution of the response to hyperthermia has led to different results depending upon the species. The thermal threshold of induction of heat shock proteins in desert thermophylic species is, as a rule, higher than in the species from less extreme climates. In addition,thermoresistant poikilothermic species often exhibit a certain level of heat shock proteins in cells even at a physiologically normal temperature. Furthermore,there is often a positive correlation between the characteristic temperature of the ecological niche of a given species and the amount of Hsp70-like proteins in the cells at normal temperature. Although in most cases adaptation to hyperthermia occurs without changes in the number of heat shock genes, these genes can be amplified in some xeric species. It was shown that mobile genetic elements may play an important role in the evolution and fine-tuning of the heat shock response system,and can be used for direct introduction of mutations in the promoter regions of these genes.