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The Zinc Finger Protein Zat12 Is Required for Cytosolic Ascorbate Peroxidase 1 Expression during Oxi

The Zinc Finger Protein Zat12 Is Required for Cytosolic Ascorbate Peroxidase 1 Expression during Oxi

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The Zinc Finger Protein Zat12 Is Required for Cytosolic Ascorbate Peroxidase 1 Expression during Oxidative Stress in Arabidopsis * S Received for publication, December 7, 2003, and in revised form, January 8, 2004 Published, JBC Papers in Press, January 13, 2004, DOI 10.1074/jbc.M313350200 Ludmila Rizhsky‡, Sholpan Davletova§, Hongjian Liang‡, and Ron Mittler§ From the Department of Botany, Plant Sciences Institute, Iowa State University, Ames, Iowa 50011 and the § Department of Biochemistry, University of Nevada, Reno, Nevada 89557 Cytosolic ascorbate peroxidase 1 (Apx1) is a key H 2 O 2 removal enzyme in plants. Microarray analysis of Apx1- deficient Arabidopsis plants revealed that the expres- sion of two zinc finger proteins (Zat12 and Zat7) and a WRKY transcription factor (WRKY25) is elevated in knock-out Apx1 plants grown under controlled condi- tions. Because mutants lacking Apx1 accumulate H 2 O 2 , we examined the correlation between H 2 O 2 and the ex- pression of Zat12, Zat7, WRKY25, and Apx1. The expres- sion of Zat12, Zat7, and WRKY25 was simultaneously elevated in cells in response to oxidative stress ( i.e. H 2 O 2 or paraquat application), heat shock, or wounding. In contrast, light or osmotic stress did not enhance the expression of these putative transcription factors. All stresses tested enhanced the expression of Apx1. Trans- genic plants expressing Zat12 or Zat7 could tolerate ox- idative stress. In contrast, transgenic plants expressing WRKY25 could not. Although the expression of Zat12, Zat7, or WRKY25 in transgenic plants did not enhance the expression of Apx1 under controlled conditions, Zat12-deficient plants were unable to enhance the ex- pression of Apx1, Zat7, or WRKY25 in response to H 2 O 2 or paraquat application. Zat12-deficient plants were also more sensitive than wild type plants to H 2 O 2 appli- cation as revealed by a higher level of H 2 O 2 -induced protein oxidation detected in these plants by protein blots. Our results suggest that Zat12 is an important component of the oxidative stress response signal trans- duction network of Arabidopsis required for Zat7, WRKY25, and Apx1 expression during oxidative stress. Plants are sessile organisms that evolved a complex and specialized network of regulatory genes to control their re- sponse to changes in environmental conditions. It is likely that many of these regulatory genes were initially created by gene duplication and that they later acquired roles specifically re- lated to individual pathways or stresses as well as their com- bination (1, 2). Different members of gene families, such as WRKY and other zinc finger proteins (72 WRKY genes and over 600 zinc finger proteins in Arabidopsis ; Ref. 3), MYB transcrip- tion factors (133 genes in Arabidopsis ; Ref. 4), and heat shock transcription factors (21 genes in Arabidopsis ; Ref. 5), were found to control and regulate diverse processes in plants rang- ing from development to response to biotic or abiotic stresses (1–5).
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