| Abstract |
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 expression of two zinc finger proteins (Zat12 and Zat7) and a WRKY transcription factor (WRKY25) is elevated in knock-out Apx1 plants grown under controlled conditions. Because mutants lacking Apx1 accumulate H(2)O(2), we examined the correlation between H(2)O(2) and the expression of Zat12, Zat7, WRKY25, and Apx1. The expression 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. Transgenic plants expressing Zat12 or Zat7 could tolerate oxidative 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 expression 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) application 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 transduction network of Arabidopsis required for Zat7, WRKY25, and Apx1 expression during oxidative stress.
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