RESUMEN
Methylmercury is a highly toxic, organic derivative found in mercury-polluted wetlands and coastal sediments worldwide. Though commonly present at low concentrations in the substrate, methylmercury can biomagnify to concentrations that poison predatory animals and humans. In the interest of developing an in situ detoxification strategy, a model plant system was transformed with bacterial genes (merA for mercuric reductase and merB for organomercurial lyase) for an organic mercury detoxification pathway. Arabidopsis thaliana plants expressing both genes grow on 50-fold higher methylmercury concentrations than wild-type plants and up to 10-fold higher concentrations than plants that express merB alone. An in vivo assay demonstrated that both transgenes are required for plants to detoxify organic mercury by converting it to volatile and much less toxic elemental mercury.
Asunto(s)
Arabidopsis/genética , Ingeniería Genética/métodos , Sustancias Peligrosas/metabolismo , Compuestos Organomercuriales/metabolismo , Plantas Modificadas Genéticamente/metabolismo , Contaminantes Atmosféricos/metabolismo , Arabidopsis/enzimología , Biodegradación Ambiental , Resistencia a Medicamentos , Ecología , Gases , Liasas/genética , Liasas/metabolismo , Mercurio/metabolismo , Compuestos de Metilmercurio/metabolismo , Compuestos de Metilmercurio/farmacología , Modelos Biológicos , Compuestos Organomercuriales/farmacología , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Fenotipo , Compuestos de Fenilmercurio/metabolismo , Compuestos de Fenilmercurio/farmacología , Contaminantes del Suelo/metabolismo , Contaminantes Químicos del Agua/metabolismoRESUMEN
Methylmercury is an environmental toxicant that biomagnifies and causes severe neurological degeneration in animals. It is produced by bacteria in soils and sediments that have been contaminated with mercury. To explore the potential of plants to extract and detoxify this chemical, we engineered a model plant, Arabidopsis thaliana, to express a modified bacterial gene, merBpe, encoding organomercurial lyase (MerB) under control of a plant promoter. MerB catalyzes the protonolysis of the carbon---mercury bond, removing the organic ligand and releasing Hg(II), a less mobile mercury species. Transgenic plants expressing merBpe grew vigorously on a wide range of concentrations of monomethylmercuric chloride and phenylmercuric acetate. Plants lacking the merBpe gene were severely inhibited or died at the same organomercurial concentrations. Six independently isolated transgenic lines produced merBpe mRNA and MerB protein at levels that varied over a 10- to 15-fold range, and even the lowest levels of merBpe expression conferred resistance to organomercurials. Our work suggests that native macrophytes (e.g., trees, shrubs, grasses) engineered to express merBpe may be used to degrade methylmercury at polluted sites and sequester Hg(II) for later removal.