title: The absence of ALTERNATIVE OXIDASE1a in Arabidopsis results in acute sensitivity to combined light and drought stress.
abstract: Treatment of Arabidopsis (Arabidopsis thaliana) alternative oxidase1a (aox1a) mutant plants with moderate light under drought conditions resulted in a phenotypic difference compared with ecotype Columbia (Col-0), as evidenced by a 10-fold increase in the accumulation of anthocyanins in leaves, alterations in photosynthetic efficiency, and increased superoxide radical 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, and sucrose and starch metabolism changed, indicating that effects were not confined to mitochondria, where the AOX1a protein is located. Microarray and quantitative reverse transcription-polymerase chain reaction analysis revealed that transcripts typically induced upon stress treatment or involved in antioxidant defense systems, especially chloroplast-located antioxidant defense components, had altered basal levels in untreated aox1a plants, suggesting a significant change in the basal equilibrium of signaling pathways that regulate these components. Taken together, these results indicate that 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.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Estelle
authors.initials: E
authors.lastname: Giraud
authors.forename: Lois H M
authors.initials: LH
authors.lastname: Ho
authors.forename: Rachel
authors.initials: R
authors.lastname: Clifton
authors.forename: Adam
authors.initials: A
authors.lastname: Carroll
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Estavillo
authors.forename: Yew-Foon
authors.initials: YF
authors.lastname: Tan
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Howell
authors.forename: Aneta
authors.initials: A
authors.lastname: Ivanova
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Pogson
authors.forename: A Harvey
authors.initials: AH
authors.lastname: Millar
authors.forename: James
authors.initials: J
authors.lastname: Whelan
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D004190:Disasters; D008401:Gas Chromatography-Mass Spectrometry; D008027:Light; D024101:Mitochondrial Proteins; D020411:Oligonucleotide Array Sequence Analysis; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis; D010940:Plant Proteins; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase