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

Abstract

Sponges (Porifera) are among the major phyla inhabiting the marine hard-substrate benthos, both in respect to the number of species and their biomass. Hence reliable biomarkers need to be developed to monitor the environmental load in those animals. Recently, the cDNA for the heat shock protein HSP70 has been isolated from the sponge Geodia cydonium and found to be a reliable indicator for temperature stress. In the present study, we have isolated the Rab GDP-dissociation inhibitor (GDI), which has previously been shown to be a key element in the intracellular traffic system. The 1521 bp long cDNA, encoding sponge GDI, has been isolated and analyzed. The deduced aa sequence ( M r = 50215) displays 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 stress; in contrast, the transcription of the sponge HSP70 is strongly enhanced. Due to the high sequence conservation of the GDIs, one can assume that sponge GDI probes can be used as functional biomarkers for temperature stress, especially when applied simultaneously with the highly conserved HSP70 probes.