FOLK, Donna G.*; GILCHRIST, George W.; The College of William and Mary; The College of William and Mary: Heat-Shock Response and Locomotory Performance in Drosophila Populations Selected for Divergent Knockdown Temperatures
The thermal environment has a critical influence on the physiological performance of all organisms. To study the impact of temperature change on performance, we have generated replicate lines of Drosophila melanogaster that are selected for high or low knockdown temperature (TKD) – that temperature at which flies lose the ability to remain upright or locomote. The up-selected TKD lines (N=4) lose these abilities at ≈41oC, while the down-selected TKD lines (N=4) lose them at ≈38oC. We hypothesize that divergence in the rate of heat shock protein (Hsp) induction and/or the magnitude of the Hsp response at stressful temperatures may mediate the evolved differences in thermotolerance. We present here a temporal profile of induced-Hsp70 expression in the high and low TKD lines following exposure to different periods of heat stress (i.e., 36oC at 10, 20, 30, or 60 minutes). Our data indicate that the high and low TKDlines have evolved divergent patterns of induced-Hsp70 expression in response to a heat pulse. Inducible Hsps, in particular Hsp70, lower synaptic thermosensitivity and protect synaptic function, and presumably locomotory performance, during periods of thermal stress in Drosophila. To examine the ability of Hsp70 to protect locomotory performance in our selected populations, we exposed the high and low TKD lines to 36 oC for 1 h (followed by 25 oC for 1 h) prior to measuring knockdown temperature. We then determined if such a pretreatment, which typically induces Hsp70 expression, allows the flies to remain upright and/or to fly at temperatures significantly higher than their characteristic TKDs.
