Poster: Heavy metals & phytoremediation

Abs # 45: From laboratory to the field: merA-expressing plants for soil and water mercury phytoremediation

Presenter:	Heaton, Andrew C.P., heaton@uga.edu
Authors	Heaton, Andrew C.P. (A)   Meagher, Richard B. (A)   Rugh, Clayton L. (C)   Merkle, Scott  (B)
Affiliations:	(A): University of Georgia, Genetics Department (B): University of Georgia, Forest Resources (C): Michigan State University, Crop and Soil Sciences

Mercury pollution is a serious threat worldwide, particularly in aquatic or marine environments where Hg(II) is efficiently converted by native bacteria to the neurotoxic and biomagnifying methylmercury. Plants transformed with a modified bacterial mercurial reductase have been developed for the phytoremediation of Hg(II)-contaminated soils and waters. Early work with merA Arabidopsis thaliana and Nictotiana tabacum demonstrated that efficient electrochemical reduction of Hg(II) to the less toxic Hg(0) confers mercuric resistance to expressing plants, and results in the volatile loss of Hg(0). Recent experiments primarily used merA N. tabacum as a model species to study the effect of MerA-expression on plant Hg(II) resistance and electrochemical processing. Compared to the wild-type, merA N. tabacum have been shown to better resist Hg(II)-induced transpiration stress, to grow at least four times more roots through concentrated Hg(II) (as HgS), to retain less mercury in tissues either from atmospheric or belowground sources, and to reduce the total mercury concentration in a polluted field soil. Because of efficient bacterial Hg(II) methylation in marine and aquatic sediments, mercury phytoremediation is most likely to involve plants that grow well in these marine or aqueous environments. Therefore, experiments are now focusing on the responses of merA O. sativa and P. deltoides to Hg(II) in soil and water, and the ability of these plants to reduce Hg(II) concentrations in greenhouse and field soils. Initial results suggest that patterns of Hg(II) resistance and electrochemical processing observed in model merA plants A. thaliana and N. tabacum seem to be representative across the more “field-practical” merA plants.