NATURAL AND GENETIC-ENGINEERING OF THE HEAT-SHOCK-PROTEIN HSP70 IN DROSOPHILA-MELANOGASTER - CONSEQUENCES FOR THERMOTOLERANCE

Larvae of the fruit fly, Drosophila melanogaster, live within necrotic fruit, a challenging environment in which larvae can experience sever e thermal stress. One response to thermal stress, the expression of he at-shock proteins (Hsps), has evolved distinctively in this species; t he gene encoding Hsp70 has undergone extensive duplication and account s for the bulk of Hsps that are expressed upon heat shock, Genetic eng ineering of hsp70 copy number is sufficient to affect thermotolerance at some (but not all) life stages. Increases in Hsp70, moreover, can p rotect intact larvae against thermal inactivation of the enzyme alcoho l dehydrogenase and thermal inhibition of feeding, Deleterious consequ ences of high Levels of Hsp70, however, may limit further evolutionary proliferation of hsp70 genes. These findings illustrate how the persp ectives of integrative and comparative biology, if applied to even wel l-studied model organisms, can lead to novel findings.