Cloning of a heat inducible biomarker, the cDNA encoding the 70 kDa heat shock protein, from the marine sponge Geodia cydonium: Response to natural stressors

The biomarker concept involves the use of biochemical, cellular and physiological parameters as screening tools in environmental surveillance. Stress proteins, such as heat shock proteins (HSPs), fulfill many of the requirements for being ideal candidates in a biomarker strategy for environmental monitoring. Sponges (Porifera) are one of the major phyla found in the marine hard-substrate benthos, both with respect to the number of species and biomass. However, only recently have genes from sponges been cloned. Here we describe the isolation of the cDNA encoding a heat shock protein of M(r) (relative molecular weight) 70 kDa (HSP70). The cDNA HSP70 from the marine sponge Geodia cydonium has a length of 2.3 kb and encodes an AA sequence of M(r) 72 579. The sponge HSP70 displays characteristic features of the HSP70 family. The HSP70 protein is induced by natural stressors including changes in temperature as well as pH, as demonstrated by Western blot analysis. No response was observed after treating the samples with hypotonic or hypertonic conditions. Our results provide the first molecular evidence that HSP70 of sponges is a useful biomarker.