Meeting Abstract
Osmoconforming estuarine bivalves modulate concentrations of intracellular free amino acids to eliminate the osmotic gradient imposed by tidal variations in environmental salinity. Before adaptation takes place, there is a transient osmotic water flux. Since locomotion is absent or restricted, as environmental salinity changes, these organisms adapt so that the intracellular osmotic concentration matches that of the environment. We are testing the hypothesis that an induced heat shock protein (Hsp(72)) is produced in gills of the ribbed mussel Geukensia demissa as part of an adaptive response to increased salinity. Heat shock proteins (HSPs) act as molecular chaperones, binding to target proteins to restrict their folding. Constitutive HSPs are used during protein translation and import. Another group of HSPs are encoded by genes whose expression is typically modulated by thermal stress, but have also been shown to respond to other forms of stress including inflammation, heavy metal or bacterial contamination. Western blots show that G. demissa is able to produce both the stress-induced Hsp(72) and the constitutively expressed Hsc(73) forms of the protein. The data also suggest that the amount of the induced form (Hsp(72)) seems to increase in the first half hour of a high-salinity exposure. A semi-quantitative reverse transcription-PCR method is being developed to determine if there are changes in expression of Hsp(72) during high-salinity adaption, and whether or not these data support the Western Blot data. Preliminary PCR findings suggest that the appropriately designed primers are able to easily discriminate between induced and constitutive forms based on predicted amplicon size (Hsp(72) = 469bp, Hsc(73) = 688bp). Data will be presented to show whether changes in salinity induce production of induced Hsp(72). Supported by a CSU-AAUP grant to MAK.
