Use of RNA-arbitrarily-primed PCR to detect the induction of gene expression in freshwater bivalves (Unio tumidus) transplanted into the Moselle River.

RNA-arbitrarily-primed PCR (RAP-PCR) can be used to detect changes in gene expression in organisms for which only minimal genomic information is available. In this study, RAP-PCR was used to detect modification of mRNA expression in the freshwater bivalve Unio tumidus, a mussel commonly used as a sentinel species in field studies. RNA expression was analyzed in the digestive glands of mussels from a control pond and in mussels transplanted into two sites on the Moselle River. The analysis identified a product in all animals exposed to sediments at the river station located downstream of a heavily populated area. This product was not present in animals exposed at the upstream station or at the control site. The additional PCR product was cloned and sequenced, and specific oligonucleotides for the sequence were designed to amplify cDNAs from control and transplanted mussels. A signal was obtained only with the cDNAs from animals exposed at the downstream station, confirming that the variation detected by RAP-PCR corresponds to an increase of gene expression. Chemical analysis of sediments from the control and river sites indicated that the levels of several potential pollutants were similar at the three locations and below currently accepted pollution thresholds. Our results indicate that RAP-PCR is a sensitive technique that can be applied in field studies to identify modifications in the gene expression of bioindicator species. This approach can complement chemical, biochemical and population studies to assess the impact of human activity on the ecological quality of aquatic systems.