Plant and Cell Physiology Advance Access originally published online on February 21, 2008
Plant and Cell Physiology 2008 49(4):592-603; doi:10.1093/pcp/pcn031
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Influence of Chloroplastic Photo-Oxidative Stress on Mitochondrial Alternative Oxidase Capacity and Respiratory Properties: A Case Study with Arabidopsis yellow variegated 2
1Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043 Japan
2Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
3Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama, 710-0046 Japan
*Corresponding author: E-mail, kyoshida{at}biol.s.u-tokyo.ac.jp; Fax, +81-3-5841-4465.
| Abstract |
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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.
Keywords: Alternative oxidase - Arabidopsis thaliana - Energy-dissipating respiration - Photo-oxidative stress - yellow variegated 2
Abbreviations: ANOVA, analysis of variance; AOX, alternative oxidase; COX, cytochrome c oxidase; CS, citrate synthase; DAB, 3,3-diaminobenzidine; DTT, dithiothreitol; HL, high light; H2O2, hydrogen peroxide; LHCII, light-harvesting complex II; LL, low light; MDA, malondialdehyde; NAD-ME, NAD-malic enzyme; NADP-MDH, NADP-malate dehydrogenase; RbcL, Rubisco large subunit; RbcS, Rubisco small subunit; ROS, reactive oxygen species; TCA, tricarboxylic acid; UCP, uncoupling protein.
4Present address: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
(Received January 24, 2008; Accepted February 18, 2008)
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