DIAGNOSIS OF SUBLETHAL STRESS IN THE MARINE SPONGE GEODIA-CYDONIUM - APPLICATION OF THE 70 KDA HEAT-SHOCK-PROTEIN AND A NOVEL BIOMARKER, THE RAB GDP DISSOCIATION INHIBITOR, AS PROBES

Sponges (Porifera) are among the major phyla inhabiting the marine har d-substrate benthos, both in respect to the number of species and thei r biomass. Hence reliable biomarkers need to be developed to monitor t he environmental load in those animals. Recently, the cDNA for the hea t shock protein HSP70 has been isolated from the sponge Geodia cycloni um and found to be a reliable indicator for temperature stress. In the present study, we have isolated the Rab GDP-dissociation inhibitor (G DI), which has previously been shown to be a key element in the intrac ellular traffic system. The 1521 bp long cDNA, encoding sponge GDI, ha s been isolated and analyzed. The deduced aa sequence (M-r = 50215) di splays high homology to vertebrate, invertebrate and also yeast GDIs. Northern blot analysis revealed that the 1.6 kb sponge transcript that hybridized with the sponge GDI is down-regulated under temperature st ress; in contrast, the transcription of the sponge HSP70 is strongly e nhanced, Due to the high sequence conservation of the GDIs, one can as sume that sponge GDI probes can be used as functional biomarkers for t emperature stress, especially when applied simultaneously with the hig hly conserved HSP70 probes.