J. Exp. Mar. Biol. Ecol. 179 (1994) 179-193 JOURNAL OF EXPERIMENTAL MARINE BIOLOQY AND ECOLODY Expression of low molecular weight HSP 70 related polypeptides from the symbiotic sea anemone Anemonia viridis Forskall in response to heat shock V. A. Sharp a**, D. Millerb, J. C. Bythell”, B. E. Browna “Department of Marine Sciences and Coastal Management, Ridley Building, University of Newcastle, Newcastle Upon Tyne. NE1 7R (I, UK; b Department of Clinical Medicine. Academic Unit of Pathology, School of Medicine, The University of Leeds, Leeds LS2 9JT, UK (Received 15 November 1993; revision received 7 February 1994; accepted 22 February 1994) Abstract Monoclonal antibodies raised against the highly conserved heat shock protein (hsp) 70 failed to detect an equivalent molecular mass homologue in the temperate sea anemone Anemonia viridis and its endosymbiotic zooxanthellae before or after heat shock. Cross-reaction does occur with a heat shock inducible 70 kDa protein in Gonioporu djiboutiensis (Vaughan), a subtidal tropical coral. Hsp 70-specific antibodies did recognise 28 kDa and 29 kDa soluble proteins from intertidal A. viridis before and after heat shock. Differential expression of these low molecular mass hsp 70 homologues in intertidal and subtidal populations correlates with thermotolerance. Anemones maintained artificially without endosymbiotic zooxanthellae are capable of synthe- sising the low molecular mass hsp homologues following heat shock, but do not express them constitutively. Key words: Heat shock; Anemonia viridis; Hsp 70 1. Introduction Up-regulation of the expression of stress or heat shock proteins (hsp) following various physico-chemical insults has been observed in almost all organisms studied to date. These proteins have been shown to be remarkably conserved throughout evolu- tion (Lindquist, 1986; Craig & Lindquist 1988) with the almost ubiquitous 70 kDa hsp * Corresponding author. 0022-0981/94/$7.00 0 1994 Elsevier Science B.V SSDI 0022-098 1(94)00028-C All rights reserved