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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Overexpression of AtCpNifS Enhances Selenium Tolerance and Accumulation in Arabidopsis¹

Biology Department, Colorado State University, Fort Collins, Colorado 80523 (D.V.H., G.F.G., A.R.A., S.E.A.-G., M.P., E.A.H.P.-S.); Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (M.A.M., S.F.); and RIKEN Plant Science Center, Tsurumi-ku, Yokohama 230–0045, Japan (K.I., E.I., H.T.)

Selenium (Se) is an essential element for many organisms but is toxic at higher levels. CpNifS is a chloroplastic NifS-like protein in Arabidopsis (Arabidopsis thaliana) that can catalyze the conversion of cysteine into alanine and elemental sulfur (S⁰) and of selenocysteine into alanine and elemental Se (Se⁰). We overexpressed CpNifS to investigate the effects on Se metabolism in plants. CpNifS overexpression significantly enhanced selenate tolerance (1.9-fold) and Se accumulation (2.2-fold). CpNifS overexpressors showed significantly reduced Se incorporation into protein, which may explain their higher Se tolerance. Also, sulfur accumulation was enhanced by approximately 30% in CpNifS overexpressors, both on media with and without selenate. Root transcriptome changes in response to selenate mimicked the effects observed under sulfur starvation. There were only a few transcriptome differences between CpNifS-overexpressing plants and wild type, besides the 25- to 40-fold increase in CpNifS levels. Judged from x-ray analysis of near edge spectrum, both CpNifS overexpressors and wild type accumulated mostly selenate (Se^VI). In conclusion, overexpression of this plant NifS-like protein had a pronounced effect on plant Se metabolism. The observed enhanced Se accumulation and tolerance of CpNifS overexpressors show promise for use in phytoremediation.

² These authors contributed equally to the paper.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Elizabeth A.H. Pilon-Smits (epsmits{at}lamar.colostate.edu).

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.068684.

^* Corresponding author; e-mail epsmits{at}lamar.colostate.edu; fax 970–491–0649.

Received July 25, 2005; returned for revision September 7, 2005; accepted September 17, 2005.

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