Analysis of gene expression as a new tool in ecotoxicology and environmental monitoring

Pollution affects biological mechanisms in exposed biota, with adverse effects on tissue, organism and, eventually, entire ecosystem levels. Ecotoxicological biomarkers reflect these pollutant-induced physiological alterations, usually by measuring changes in the activity of specific enzymes, or alterations in hormone or protein levels. New, robust polymerase-chain-reaction (PCR)-based methodologies for quantifying specific messenger-RNA molecules have allowed the development of a new family of biomarkers based on analysis of gene-expression patterns. These gene-expression biomarkers have already been applied to many aspects of risk assessment, from toxicological analyses of new substances to in-field monitoring schemes. We review the fundamentals of these techniques, their application in different environmental surveys, their limitations and the outlook for their use in the future.