COMBINATORY EFFECTS OF TEMPERATURE STRESS AND NONIONIC ORGANIC POLLUTANTS ON STRESS PROTEIN (HSP70) GENE-EXPRESSION IN THE FRESH-WATER SPONGE EPHYDATIA-FLUVIATILIS

This is the first documentation of a heat shock protein (hsp) response in sponges. Subjecting the freshwater sponge Ephydatia fluviatilis to temperature stress (18 degrees to 33 degrees C; 2 h) resulted in an i ncreased expression (> 10 times) of the M(r) 70,000 (hsp70). The induc tion of hsp70 could be demonstrated on the level of gene expression an d by quantification of the hsp70 protein. Temperature stress also resu lted in a 25% reduction of sponge cell proliferation. A mixture of non ionic organic compounds was extracted from water from the polluted Sch warzbach River (S. Hesse, Germany) by adsorption onto XAD-7 resin. Con centrations of this Schwarzbach River water extract at two and four ti mes ambient levels resulted in decreases in cell proliferation by 53.6 and 99.4%, respectively. However, when cells were exposed to these le vels of the Schwarzbach River water extract directly following a tempe rature stress (33 degrees C for 2 h), cell proliferation was less affe cted by the extract than the absence of the temperature stress. In add ition, the combination of temperature stress and exposure to the Schwa rzbach River water extract resulted in higher levels of hsp70 than wer e observed for each stressor by itself. Northern and Western blotting as well as precipitation assays confirmed the interaction between heat treatment and exposure to different amounts of nonionic organic pollu tants on the level of mRNA and protein expression of hsp70. From these data we conclude that a sublethal treatment of sponges with heat resu lts in a higher tolerance of the animals to chemical stressors. These results are relevant to the real-world situation where organisms are o ften exposed simultaneously to a variety of stressors, in contrast to many laboratory exposures that aim to elucidate the effects of individ ual stressors.