IMMEDIATE-EARLY RESPONSE OF THE MARINE SPONGE SUBERITES DOMUNCULA TO HEAT-STRESS - REDUCTION OF TREHALOSE AND GLUTATHIONE CONCENTRATIONS AND GLUTATHIONE-S-TRANSFERASE ACTIVITY

The marine sponge Suberites domuncula was used to identify early marke rs fdr thermal stress. Cubes from sponges have been kept for 30 min at 31 degrees C (10 degrees C higher than the ambient temperature). Afte r this treatment the sponge cubes were kept again at 21 degrees C. To demonstrate that the animals reacted to the elevated temperature, the expression of heat shock protein (HSP) was determined. Using an antibo dy raised against HSP70, it was found by Western blotting that the ani mals specifically express a 45 kDa polypeptide after heat treatment. I t was shown that even after 10 min of heat treatment the steady-state concentration of trehalose drops by 40% from a base level of 13 nmol/m g protein. The activity of the trehalose-degrading enzyme, trehalase, remained unchanged. Additional early biomarkers for thermal stress inc lude the enzyme activity of glutathione S-transferase (GST) and the co ncentration of glutathione (GSH). After 5-min the activity of GST decr eased by 40%. Similarly, the concentration of GSH dropped by 50% after 15 to 20 min exposure. The orginal levels of the biomarkers, trehalos e, GSH and GST, were reached again after a recovery period of about 18 0 min. By contrast, the steady-state concentration of polyphosphates d id not change during heat treatment. These data show that in S. domunc ula the concentrations of trehalose, GSH, and the activity of GST, are biomarkers for immediate early response towards heat stress. Copyrigh t (C) 1997 Elsevier Science B.V.