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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Arabidopsis Putative Selenium-Binding Protein1 Expression Is Tightly Linked to Cellular Sulfur Demand and Can Reduce Sensitivity to Stresses Requiring Glutathione for Tolerance^1,[W]

Laboratoire de Physiologie Cellulaire Végétale, UMR 5168, Commissariat à l'Energie Atomique/CNRS/Université Joseph-Fourier/INRA, Institut de Recherches en Technologies et Sciences pour le Vivant, Commissariat à l'Energie Atomique-Grenoble, 38054 Grenoble cedex 9, France

Selenium-Binding Protein1 (SBP1) gene expression was studied in Arabidopsis (Arabidopsis thaliana) seedlings challenged with several stresses, including cadmium (Cd), selenium {selenate [Se(VI)] and selenite [Se(IV)]}, copper (Cu), zinc (Zn), and hydrogen peroxide (H₂O₂) using transgenic lines expressing the luciferase (LUC) reporter gene under the control of the SBP1 promoter. In roots and shoots of SBP1::LUC lines, LUC activity increased in response to Cd, Se(VI), Cu, and H₂O₂ but not in response to Se(IV) or Zn. The pattern of expression of SBP1 was similar to that of PRH43, which encodes the 5'-Adenylylphosphosulfate Reductase2, a marker for the induction of the sulfur assimilation pathway, suggesting that an enhanced sulfur demand triggers SBP1 up-regulation. Correlated to these results, SBP1 promoter showed enhanced activity in response to sulfur starvation. The sulfur starvation induction of SBP1 was abolished by feeding the plants with glutathione (GSH) and was enhanced when seedlings were treated simultaneously with buthionine sulfoxide, which inhibits GSH synthesis, indicating that GSH level participates in the regulation of SBP1 expression. Changes in total GSH level were observed in seedlings challenged with Cd, Se(VI), and H₂O₂. Accordingly, cad2-1 seedlings, affected in GSH synthesis, were more sensitive than wild-type plants to these three stresses. Moreover, wild-type and cad2-1 seedlings overexpressing SBP1 showed a significant enhanced tolerance to Se(VI) and H₂O₂ in addition to the previously described resistance to Cd, highlighting that SBP1 expression decreases sensitivity to stress requiring GSH for tolerance. These results are discussed with regard to the potential regulation and function of SBP1 in plants.

² These authors contributed equally to the article.

³ Present address: Laboratoire de Physiologie Cellulaire et Moléculaire des Plantes, UR 5 UPMC-EAC 7180 CNRS Université Pierre et Marie Curie 3, rue Galilée Le Raphaël, 94200 Ivry sur Seine, France.

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: Véronique Hugouvieux (veronique.hugouvieux{at}cea.fr).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.144808

^* Corresponding author; e-mail veronique.hugouvieux{at}cea.fr.

Received July 15, 2009; accepted August 24, 2009; published August 26, 2009.