Phytodetoxification of hazardous organomercurials by genetically engineered plants

Methylmercury is a highly toxic, organic derivative found in mercury-pollut ed wetlands and coastal sediments worldwide. Though commonly present at low concentrations in the substrate, methylmercury can biomagnify to concentra tions that poison predatory animals and humans. In the interest of developi ng an in situ detoxification strategy, a model plant system was transformed with bacterial genes (merA for mercuric reductase and merB for organomercu rial lyase) for an organic mercury detoxification pathway. Arabidopsis thal iana plants expressing both genes grow on 50-fold higher methylmercury conc entrations than wild-type plants and up to 10-fold higher concentrations th an plants that express merB alone. An in vivo assay demonstrated that both transgenes are required for plants to detoxify organic mercury by convertin g it to volatile and much less toxic elemental mercury.