Heavy Metals and Phytoremediation
Sundaram, Sabarinath , Rathinasabapathi, Bala , Ma, Lena , Rosen, Barry .
An unusual glutaredoxin from the arsenic hyperaccumulator fern Pteris vittata L. regulates intracellular arsenite.
To elucidate the mechanisms of arsenic resistance in the arsenic hyperaccumulator fern Pteris vittata L., a cDNA for a glutaredoxin (Grx) Pv5-6 was isolated from a frond expression cDNA library based on the cDNA’s ability to increase arsenic resistance in Escherichia coli.The deduced amino acid sequence of Pv5-6 contained two CXXS putative catalytic motifs. Purified recombinant Pv5-6 exhibited glutaredoxin activity that was increased 1.8-fold by 10 mM arsenate. Site-specific mutation of Cys67 to Ala67 resulted in the loss of both GRX activity and arsenic resistance. PvGrx5 was expressed in E.coli mutants in which the arsenic resistance genes of the ars operon were deleted (strain AW3110), a deletion of the gene for the ArsC arsenate reductase (strain WC3110), and a strain in which both the ars operon and the gene for the GlpF aquaglyceroporin were deleted (strain OSBR1). Expression of PvGrx5 increased arsenic tolerance in strains AW3110 and WC3110, but not in OSBR1, suggesting that PvGrx5 had a role in cellular arsenic resistance independent of the ars operon genes but dependent on GlpF. Cells expressing PvGrx5 had significantly lower levels of arsenite compared to vector controls when cultured in medium containing 2.5 mM arsenate. Our results are consistent with PvGrx5 having a role in regulating intracellular arsenite levels, either by directly or indirectly modulating the aquaglyceroporin. To our knowledge, PvGrx5 is the first plant Grx implicated in arsenic metabolism.
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1 - University of Florida, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, Gainesville, Florida, 32611-0690, USA
2 - University of Florida, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department
3 - University of Florida, Soil and Water Science Department
4 - Wayne State University, Department of Biochemistry and Molecular Biology
Presentation Type: ASPB Minisymposium
Location: Continental C/Hilton
Date: Monday, July 9th, 2007
Time: 9:20 AM