Accumulation of mercury in transgenic tobacco expressing bacterial polyphosphate

The feasibility of transgenic tobacco, engineered to express bacterial polyphosphate (polyP), for phytoremediation of mercury pollution was evaluated. T-3 progeny of the transgenic tobacco produced a large amount of polyP in leaves and showed a relatively high resistant phenotype to Hg2+ than its wild-type progenitors. These results suggest that the integrated ppk gene, encoding polyphosphate kinase (PPK), a key enzyme for polyP biosynthesis, is stably conserved in tobacco genome, and translated to active PPK which catalyzed biosynthesis of polyP, and suggest that polyP is capable of reducing the cytotoxicity of Hg2+, probably via chelation formation with polyP. The transgenic tobacco expressing polyP accumulated significantly more mercury than its wild-type progenitors from Hg2+-containing agar medium and simulated soils without taxing the tobacco plants suggesting that the transported Hg2+ was accumulated as a less toxic Hg-polyP complex in the tobacco tissues. Based on the results obtained in the present study, the polyP-mediated accumulation of mercury from mercurial-contaminated soils may provide an ecologically compatible approach for phytoremediation of mercury pollution.