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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

AtOSA1, a Member of the Abc1-Like Family, as a New Factor in Cadmium and Oxidative Stress Response^1,[W],[OA]

University of Zurich, Institute of Plant Biology, 8008 Zurich, Switzerland (M.J., D.S., M.S., E.M.); University of Bern, IPS-Plant Nutrition, 3012 Bern, Switzerland (D.S., S.C., L.B.); University of Geneva, Bioenergetics Laboratory, 1254 Jussy/Lullier, Switzerland (G.S.); University of Fribourg, Department of Biology-Plant Biology, 1700 Fribourg, Switzerland (L.B.); and Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61–704 Poznan, Poland (M.J.)

The analysis of gene expression in Arabidopsis (Arabidopsis thaliana) using cDNA microarrays and reverse transcription-polymerase chain reaction showed that AtOSA1 (A. thaliana oxidative stress-related Abc1-like protein) transcript levels are influenced by Cd²⁺ treatment. The comparison of protein sequences revealed that AtOSA1 belongs to the family of Abc1 proteins. Up to now, Abc1-like proteins have been identified in prokaryotes and in the mitochondria of eukaryotes. AtOSA1 is the first member of this family to be localized in the chloroplasts. However, despite sharing homology to the mitochondrial ABC1 of Saccharomyces cerevisiae, AtOSA1 was not able to complement yeast strains deleted in the endogenous ABC1 gene, thereby suggesting different function between AtOSA1 and the yeast ABC1. The atosa1-1 and atosa1-2 T-DNA insertion mutants were more affected than wild-type plants by Cd²⁺ and revealed an increased sensitivity toward oxidative stress (hydrogen peroxide) and high light. The mutants exhibited higher superoxide dismutase activities and differences in the expression of genes involved in the antioxidant pathway. In addition to the conserved Abc1 region in the AtOSA1 protein sequence, putative kinase domains were found. Protein kinase assays in gelo using myelin basic protein as a kinase substrate revealed that chloroplast envelope membrane fractions from the AtOSA1 mutant lacked a 70-kD phosphorylated protein compared to the wild type. Our data suggest that the chloroplast AtOSA1 protein is a new factor playing a role in the balance of oxidative stress.

² These authors contributed equally to the article.

³ Present address: Philip Morris Products S.A., PMI Research & Development, Quai Jeanrenaud 56, 2000 Neuchâtel, Switzerland.

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: Lucien Bovet (lucien.bovet{at}pmintl.com).

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

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.110247

^* Corresponding author; e-mail lucien.bovet{at}pmintl.com.

Received October 1, 2007; accepted March 20, 2008; published April 4, 2008.