Ecological and Evolutionary Physiology of the Stress Response and Stress Proteins

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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 in part uses the heat-shock protein Hsp70 in Drosophila as a model trait/organism/system to address this issue. In response to heat or other stresses, nearly all organisms express heat-shock proteins (I-Isps), highly-conserved proteins that contribute to stress tolerance by functioning as molecular chaperones. Research supported by previous NSF awards has established that experimental manipulation of copy number of the hsp7O gene of Drosophila, which encodes Hsp7O, is sufficient to cause changes in outright survival of natural thermal stress, and that natural populations vary in Hsp70 expression in ways that are consistent with it being adaptive. The proposed research will build upon a recent and significant preliminary finding: that not only does Hsp70 protect against heat death, it also mitigates major morphological anomalies in wings and abdomens of adults that have undergone exposure to natural thermal stress during their pre-adult stages. Such morphological abnormalities can occur in 10% of surviving adults and potentially compromise courtship and mating, territorial defense, oviposition, flight, and water balance, each a likely component of fitness. The proposed research will first relate the incidence of these abnormalities to the temperatures that non-adult Drosophila undergo in the laboratory, and then verify that similar relationships occur for Drosophila in nature. Next, the proposed research will establish the effect of these abnormalities on courtship and mating, territorial defense, oviposition, flight, and water balance. Finally, the proposed experiment will genetically and experimentally manipulate Hsp expression to establish the role of Hsp7O in protecting or mitigating morphological defects. The projected outcome of the proposed research has immense potential to integrate molecular, genetic, functional, and evolutionary perspectives to advance understanding of adaptation.