Partners and International Organizations
(English)
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AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GR, HU, IE, IL, IT, LT, LU, NL, NO, PL, PT, RO, SE, SI, SK, TR, UK
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Abstract
(English)
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Based on a microchip analysis we identified several genes differentially regulated by Cd2+. In the frame of this COST action we focused on a member of the Abc1 faily, AtOSA1, and a member of the ABC transporter family, AtATH12. 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. The atosa1-1 and atosa1-2 T-DNA insertion mutants were more affected than wild type plants by Cd2+ and revealed an increased sensitivity towards oxidative stress (H2O2) 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 a balance of oxidative stress. In case of AtATH12 we could show that this gene product is localized in the chloroplast. Mutant plants exhibit several phenotypes: They are more sensitive to Cd2+ and Al3+,and exhibit a chlorotic phenotype when exposed to Cd2+. Further investgations lead us to hypothesize that AtATH12 is involved in iron transport and homeostasis. Actually we are performing experiments to look at this aspect more in detail.
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