Elevated temperature and solar radiation, including ultraviolet radiation, are now recognized as the primary environmental stresses that lead to mass cnidarian bleaching. This study takes a functional genomics approach to identifying genes that change expression soon after exposure to these stressors in the temperate sea anemone Anthopleura elegantissima that harbors Symbiodinium, the same genus of symbionts found in reef-building corals. Symbiotic anemones were subjected to elevated temperature or UV over a 24 h period. cDNA from these animals was hybridized to a 10,000-feature cDNA microarray of A. elegantissima. Overall 2.7% of the 10,000 features were found to be differentially expressed as a function of temperature or UV stress. Of the 86 features sequenced, 45% displayed significant homology to sequences in GenBank. There are 27 features that were differentially expressed in both stress conditions. Gene ontology analysis placed the differentially expressed genes in a wide range of categories including cytoskeleton organization and biogenesis, protein biosynthesis, cell proliferation, apoptosis and transport. This suggests that the early stress response to elevated temperature and UV involves essentially all aspects of host cellular regulation and machinery and that downstream cnidarian bleaching is a complex cellular response in host tissues.
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