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Plant Physiology Preview Published on March 2, 2007; 10.1104/pp.106.093328
OPEN ACCESS ARTICLE
Received November 19, 2006 The Rimb (Redox Imbalanced)-mutants of Arabidopsis Differentiate Signalling Pathways for Redox-regulation of Chloroplast Antioxidant Enzymes
Biochemistry and Physiology of Plants, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany; Cell Biology, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany; Zentrum für ultrastrukturelle Diagnostik im IIT, Universitätsstraße 25, 33615 Bielefeld, Germany; Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, England * Corresponding author; email: margarete.baier{at}uni-bielefeld.de.
A network of enzymatic and non-enzymatic antioxidants protects chloroplasts from photo-oxidative damage. With all enzymatic components being nuclear encoded, the control of the antioxidant capacity depends on chloroplast-to-nucleus redox signalling. Using an Arabidopsis reporter gene line expressing luciferase under control of the redox sensitive 2-Cys peroxiredoxin A (2CPA) promoter, six mutants with low 2CPA promoter activity were isolated, of which five mutants show limitations in redox-box regulation of the 2CPA promoter. In addition to 2CPA, the transcript levels for other chloroplast antioxidant enzymes were decreased, although a higher oxidation status of the ascorbate pool, a higher reduction state of the plastoquinone pool and an increased oxidation status of the 2-Cys peroxiredoxin pool demonstrated photooxidative stress conditions. Greening of the mutants, chloroplast ultra-structure, steady state photosynthesis, and the responses to the stress hormone ABA were wildtype-like. In the rosette state, the mutants were more sensitive to low CO2 and to H2O2. Comparison of gene expression patterns and stress sensitivity characterizes the mutants as redox-imbalanced in the regulation of nuclear encoded chloroplast antioxidant enzymes and differentiates redox signalling cascades.
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