Heat Shock Gene Expression: An Indicator of Thermal Stress in Marine Animals

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Environmental regulation of gene expression is certain to be critical for the survival and success of marine organisms. At present, however, very little is known about the interactions between environmental factors, e.g., temperature, and the regulation of transcription of genes in any marine eucaryotic organism. The only well understood example of environmental control of gene expression is in the case of the heat shock proteins (HSPs), which are induced by high temperature and other stresses (e.g., anoxia) in all organisms so far studied. However, few marine species have been examined. This project will examine the heat shock gene (HSP) system in several species of differently thermally-adapted marine animals to determine: (i) the threshold temperatures at which heat stress (HSP induction) takes place in differently adapted species (or populations), (ii) the induction patterns of HSPs in larval and adult individuals of coastal fishes, and (iii) the underlying molecular bases of the inter-specific (or inter-population) differences in HSP expression. Particular attention will be given to congeneric species inhabiting different thermal regimes, e.g., latitudinally separated species of two genera of fish, Sebastes and Embiotoca, the mussel Mytilus, and to various fishes whose larval stages inhabit potentially warm bays and estuaries. The goals of these studies include (i) the development of a powerful molecular index for gauging environmental stress; (ii) the discovery of basic mechanisms of thermal tolerance, and (iii) the elucidation of evolutionary differences in the HSP regulatory mechanisms, which set the differences in induction temperatures in differently- adapted species. HSP induction temperatures may provide important insights into the thermal tolerance of different species and populations, i.e., into the fundamental molecular basis for biogeographical distribution patterns. The development of a relatively simple screening method for HSP in invertebrates, could provide a useful method for gauging the level of stress experienced by natural populations of marine organisms.