TOMANEK, L.*; SOMERO, G.N.: Heat-shock protein (hsp) 70 and promoter sequences in species of the genus Tegula from widely differing thermal environments

Marine gastropod species of the genus Tegula occupy widely differing thermal environments along the transition from the sub- to the intertidal zone. Corresponding with these differences in vertical zonation are findings that the mid-intertidal T. funebralis shows a higher thermotolerance as well as a higher induction and upper temperature of hsp synthesis, following acclimation to a common temperature than do the two subtidal species, T. brunnea and T. montereyi. In addition, in nature T. funebralis experiences temperatures that induce the stress response more frequently than the two subtidal species, which suggests that it activates the stress response more frequently under in vivo conditions. Previous research has also shown that T. funebralis activates the stress response and recovers much faster from a stress-inducing temperature exposure typical for the mid-intertidal than the subtidal T. brunnea. To investigate the molecular mechanisms that underlie these differences in stress response activation we sequenced the promoter region and the complete cytosolic hsp70 mRNA of T. funebralis. The promoter region contains a heat-shock element (HSE), which is a binding region for the heat-shock factor. By binding to the HSE, heat-shock factor activates transcription of hsp genes. A comparison of 65% of the hsp70 gene among all three congeners shows three non-synonymous changes in amino acid primary structure in the far C-terminal region only. This region may be important in the conversion of active hsp70 monomers into inactive oligomers following a stress response. We are currently elucidating the remaining hsp70 and promoter sequences for T. brunnea and T. montereyi.