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Plant Physiology Preview Published on April 18, 2008; 10.1104/pp.107.115121
OPEN ACCESS ARTICLE
Received December 23, 2007 The absence of Alternative Oxidase 1a in Arabidopsis thaliana results in acute sensitivity to combined light and drought stress
ARC Centre of Excellence in Plant Energy Biology, MCS Building M316 University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia; ARC Centre of Excellence in Plant Energy Biology, School of Biochemistry and Molecular Biology, The Australian National University, Canberra, A. C. T 0200, Australia * Corresponding author; email: seamus{at}cyllene.uwa.edu.au.
Treatment of alternative oxidase 1a mutant plants (aox1a) with moderate light under drought conditions resulted in a phenotypic difference compared to Col-0, evidenced by a 10-fold increase in the accumulation of anthocyanins in leaves, alterations in photosynthetic efficiency, increased O2- and reduced root growth at the early stages of seedling growth. Analysis of metabolite profiles revealed significant changes upon treatment in aox1a plants typical of combined stress treatments and these were less pronounced or absent in Col-0 plants. These changes were accompanied by alteration in the abundance of a variety of transcripts during the stress treatment, providing a molecular fingerprint for the stress-induced phenotype of aox1a plants. Transcripts encoding proteins involved in the synthesis of anthocyanins, transcription factors, chloroplastic and mitochondrial components, cell wall synthesis, sucrose and starch metabolism changed indicating that effects were not confined to mitochondria where the AOX1a protein is located. Microarray and QRT-PCR analysis revealed that transcripts typically induced upon stress treatment or involved in anti-oxidant defence systems, especially chloroplast located anti-oxidant defence components, had altered basal levels in untreated aox1a plants, suggesting a significant change in the basal equilibrium of signalling pathways that regulate these components. Taken together, these results indicate aox1a plants have a greatly altered stress response even when mitochondria or the mitochondrial electron transport chain are not the primary target of the stress and that AOX1a plays a broad role in determining the normal REDOX balance in the cell.
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