BARUA, D*; HECKATHORN, SA; Univ. of Toledo: Ecological Patterns and Phenotypic Plasticity in the Temperature Set-Points of the Heat-Shock Response
The evolutionarily conserved and ubiquitous heat-shock response (HSR) protects cellular components from damage. Analyzing results from diverse organisms, with growth temperatures spanning the range of temperatures known to sustain life, we show strong positive linear relationships between growth temperature (GT), and both temperatures of HSR induction (Ton) and shut-off (Toff). However, the increase in temperature required to induce the HSR (threshold = Ton -GT), and the breadth of temperatures over which the HSR is observed (Toff – Ton), decreases with increasing GT. The decreasing relationship of HSR threshold with temperatures was near universal among eukaryotic taxa, but there was no relationship for prokaryotes. HSR thresholds and breadths differed for organisms from different thermal niches. Additionally, we investigated whether plasticity of the HSR set-points is common to all organisms, and whether it varies with thermal niche. Unexpectedly, sessile organisms exhibited lower acclimation in HSR induction temperatures compared to mobile organisms, and there was no difference in acclimation between eurytherms and stenotherms. The extent of acclimation differed among the HSR temperature set-points. We show that HSR induction temperatures change in a step-wise fashion in response to changes in growth temperature. These results indicate that the HSR plays an important role in adaptation to the thermal environment and determining the biogeographic distribution of organisms.
