Feder 9723298 A major issue in ecological and evolutionary physiology is the relationship among the traits of complex organisms, organisms' ability to exploit diverse environments, and species' persistence in time. The proposed investigation examines the heat-shock protein Hsp70 in Drosophila to address this issue. In response to heat or other stresses, nearly all organisms express heat-shock proteins (Hsps), highly-conserved proteins that contribute to stress tolerance by functioning as molecular chaperones. Research supported by a previous NSF award has established that experimental manipulation of copy number of the hsp70 gene of Drosophila, which encodes Hsp70, is sufficient to cause changes in thermotolerance. The proposed research will build upon this finding to examine three related issues whose simultaneous resolution is possible in few other systems: (1) The physiological mechanism of Hsp70 function; i.e., how thermal stress disrupts function and how Hsp70 protects against heat damage or aids recovery from it. This issue will be examined in the larval gut of Drosophila, which is especially susceptible to heat damage. (2) The fitness consequences of Hsp70 expression, which will be examined by comparing survival and offspring production when Drosophila strains differing in Hsp70 expression are exposed to natural thermal stress. (3) The evolutionary basis for variation in Hsp70, which will be examined by measuring Hsp70 expression, hsp70 copy number, and the temperature threshold for Hsp70 expression in natural and experimental populations. To accomplish these goals, the proposed research will examine genetically engineered and natural variation in Drosophila. The projected outcome of the proposed research has immense potential to integrate molecular, genetic, functional, and evolutionary perspectives to advance understanding of adaptation.
