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Exploring the role of the thioredoxin system, peroxiredoxins and glutaredoxins in aluminum and cadmium tolerance in yeast and Arabidopsis thaliana Open Access

Descriptions

Other title
Subject/Keyword
aluminum
antioxidant
thioredoxin reductase
signaling
yeast
cadmium
Arabidopsis
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Lopez Santiago, Diana Laura
Supervisor and department
Taylor, Gregory (Biological Sciences)
Examining committee member and department
Deyholos, Michael (Biological Sciences)
Kav, Nat (Agricultural Food and Nutritional Science)
Yamamoto Yoko (Plant Science)
Cooke, Janice (Biological Sciences)
Department
Department of Biological Sciences
Specialization

Date accepted
2011-09-30T17:33:51Z
Graduation date
2011-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Aluminum (Al) and cadmium (Cd) are non-redox active metal ions of agricultural importance. Both are able to induce oxidative damage as a mechanism of toxicity. To increase our understanding of the mechanisms of Al and Cd toxicity and tolerance in plants, the potential role of antioxidant enzymes of the thioredoxin system, peroxiredoxins and glutaredoxins in Al and Cd tolerance was investigated in yeast (Saccharomyces cerevisiae) and Arabidopsis thaliana. Single and multiple mutants defective in genes of the thioredoxin system, peroxiredoxins and glutaredoxins in yeast were used to identify relevant genes in Al and Cd tolerance. A mutant defective in cytoplasmic thioredoxin reductase (TRR1) showed the most hypersensitive phenotype and increased levels of lipid peroxidation upon Al and Cd exposure. Transcript levels of TRR1 increased with increasing concentrations of Al and Cd. Complementation of the trr1Δ mutant with the wild-type TRR1 gene was able to restore growth to WT levels in the presence of Al and Cd. These results suggest that thioredoxin reductases are relevant genes in Al and Cd tolerance in yeast and that these genes might be also relevant in Al and Cd tolerance in plants. The role of NADPH-thioredoxin reductases (NTRs) in Al and Cd tolerance was further investigated in Arabidopsis thaliana. Among the mutants studied in Arabidopsis, only lines defective in NTRs (NTRA and NTRB) showed reduced growth compared to WT upon Al and Cd exposure. NTRA and NTRB mutants also showed increased levels of Al- and Cd-induced lipid peroxidation compared to WT. However, NTRA and NTRB transcript levels did not show a clear induction with increasing concentrations of Al and Cd. NTRA and NTRB were overexpressed in Arabidopsis to test whether increased expression of NTRs confers increased tolerance to Al and Cd. Only lines overexpressing NTRA showed increased transcript, protein and enzyme activity levels. However, these lines did not show increased tolerance to Al and Cd. My results suggest that NTRs might not be important ROS scavengers upon Al and Cd exposure, but they may play a role as a signal transducer and modulate other antioxidant enzymes.
Language
English
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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File author: Diana Lopez-Santiago
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