title: Influence of chloroplastic photo-oxidative stress on mitochondrial alternative oxidase capacity and respiratory properties: a case study with Arabidopsis yellow variegated 2.
abstract: Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes the energy-wasteful cyanide (CN)-resistant respiration. Although it has been demonstrated that leaf AOX is up-regulated under high-light (HL) conditions, the in vivo mechanism of AOX up-regulation by light is still unknown. In the present study, we examined whether the photo-oxidative stress in the chloroplast modulates mitochondrial respiratory properties, especially the AOX capacity, using Arabidopsis leaf-variegated mutant yellow variegated 2 (var2) and exposing plants to HL. var2 mutants lack FtsH2 metalloprotease required for the repair of damaged PSII. Indeed, var2-1 suffered from photo-oxidative stress even before the HL treatments. While the activities of tricarboxylic acid cycle enzymes and cytochrome c oxidase in var2-1 were almost identical to those in the wild type, the amount of AOX protein and the CN-resistant respiration rate were higher in var2-1. Real-time PCR analysis revealed that HL treatment induced the expression of some energy-dissipating respiratory genes, including AOX1a, NDB2 and UCP5, more strongly in var2-1. Western blotting using var2-1 leaf extracts specific to green or white sectors, containing functional or non-functional photosynthetic apparatus, respectively, revealed that more AOX protein was induced in the green sectors by the HL treatment. These results indicate that photo-oxidative stress by excess light is involved in the regulation of respiratory gene expression and the modulation of respiratory properties, especially the AOX up-regulation.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan. kyoshida@biol.s.u-tokyo.ac.jp
authors.forename: Keisuke
authors.initials: K
authors.lastname: Yoshida
authors.forename: Chihiro
authors.initials: C
authors.lastname: Watanabe
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kato
authors.forename: Wataru
authors.initials: W
authors.lastname: Sakamoto
authors.forename: Ko
authors.initials: K
authors.lastname: Noguchi
mesh_terms: D049069:ATP-Dependent Proteases / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D019069:Cell Respiration / Q000187:drug effects / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008027:Light; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects; D050538:Malate Dehydrogenase (NADP+) / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D024101:Mitochondrial Proteins; D009154:Mutation / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D010088:Oxidoreductases / Q000378:metabolism*; D010641:Phenotype; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D010940:Plant Proteins; D000099188:Alternative Oxidase
chemical_list: D049069:ATP-Dependent Proteases; D029681:Arabidopsis Proteins; D002734:Chlorophyll; D006861:Hydrogen Peroxide; D050538:Malate Dehydrogenase (NADP+); D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase; C402651:AT2G30950 protein, Arabidopsis