Arabidopsis chloroplastic ascorbate peroxidase isoenzymes play a dual role in photoprotection and gene regulation under photooxidative stress.
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.
Maruta
Takanori
T
Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, Nakamachi, Nara, 631-8505 Japan.
Tanouchi
Aoi
A
Tamoi
Masahiro
M
Yabuta
Yukinori
Y
Yoshimura
Kazuya
K
Ishikawa
Takahiro
T
Shigeoka
Shigeru
S
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
D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D007527:Isoenzymes; D018749:RNA, Plant; D006861:Hydrogen Peroxide; D010544:Peroxidases; C555297:APXS protein, Arabidopsis; D060387:Ascorbate Peroxidases