INDUCED THERMOTOLERANCE AND THE HEAT-SHOCK-PROTEIN-70 FAMILY IN THE PACIFIC OYSTER CRASSOSTREA-GIGAS

Commercially important oysters are often subject to mass mortality in the field. Rationalizing that heat shock can induce tolerance to stres ses other than heat, we are exploring the possibility that this treatm ent might improve subsequent survival in the field. In characterizing the heat shock response in the laboratory, we found that heat shock of 37 degrees C for 1 h (HS) enabled Pacific oysters (Crassostrea gigas) to survive an otherwise lethal heat treatment (43 degrees-44 degrees C, 1 h) (LHT). This induced thermotolerance was retained for at least 2 weeks, the longest period examined. Stress proteins of the 70-kDa fa mily were studied in gills by conventional autoradiography and immunob lotting techniques. Two constitutive isoforms of 77 and 72 kDa were up -regulated, and a 69-kDa protein was induced by HS, its synthesis occu rring during and after that treatment. Synthesis of these three protei ns was reduced to control levels within 2 days after HS, but their amo unts remained higher than in control gills for 2 weeks following HS. I mmunolocalization of proteins of the heat stock protein-70 (hsp-70) fa mily in histologic sections of gills was consistent with results from Western blotting.