title: Arabidopsis chloroplastic ascorbate peroxidase isoenzymes play a dual role in photoprotection and gene regulation under photooxidative stress.
abstract: Though two types of chloroplastic ascorbate peroxidase (APX) located in the thylakoid membrane (tAPX) and stroma (sAPX) have been thought to be key regulators of intracellular levels of H(2)O(2), their physiological significance in the response to photooxidative stress is still under discussion. Here we characterized single mutants lacking either tAPX (KO-tAPX) or sAPX (KO-sAPX). Under exposure to high light or treatment with methylviologen under light, H(2)O(2) and oxidized proteins accumulated to higher levels in both mutant plants than in the wild-type plants. On the other hand, the absence of sAPX and tAPX drastically suppressed the expression of H(2)O(2)-responsive genes under photooxidative stress. Interestingly, the most marked effect of photooxidative stress on the accumulation of H(2)O(2) and oxidized protein and gene expression was observed in the KO-tAPX plants rather than the KO-sAPX plants. The present findings suggest that both chloroplastic APXs, but particularly tAPX, are important for photoprotection and gene regulation under photooxidative stress in Arabidopsis leaves.
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, Nakamachi, Nara, 631-8505 Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.forename: Aoi
authors.initials: A
authors.lastname: Tanouchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tamoi
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Yabuta
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060387:Ascorbate Peroxidases; D060365:Chloroplast Proteins; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000528:radiation effects; D018749:RNA, Plant / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D007527:Isoenzymes; D018749:RNA, Plant; D006861:Hydrogen Peroxide; D010544:Peroxidases; C555297:APXS protein, Arabidopsis; D060387:Ascorbate Peroxidases