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Plant Physiology Preview Published on March 10, 2006; 10.1104/pp.105.075416
Received December 11, 2005 Mitogen-Activated Protein Kinase Is Involved in Abscisic Acid- Induced Antioxidant Defense and Acts downstream of Reactive Oxygen Species Production in Leaves of Maize Plants
College of Life Sciences, Nanjing Agricultural University, Nanjing, People's Republic of China * Corresponding author; email: myjiang{at}njau.edu.cn.
The role of mitogen-activated protein kinase (MAPK) in abscisic acid (ABA)-induced antioxidant defense was investigated in leaves of maize (Zea mays L.) plants. Treatments with ABA or H2O2 induced the activation of a 46 kDa MAPK and enhanced the expression of the antioxidant genes CAT1, cAPX and GR1 and the total activities of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD). Such enhancements were blocked by the pretreatment with several MAPKK inhibitors and reactive oxygen species (ROS) inhibitors or scavengers. Pretreatment with MAPKK inhibitors also substantially arrested the ABA-induced H2O2 production after 2 h of ABA treatment, but did not affect the levels of H2O2 within the first 1 h of ABA treatment. Pretreatment with several inhibitors of protein tyrosine phosphatase (PTP), which is believed to be a negative regulator of MAPK, only slightly prevented the ABA-induced H2O2 production, but did not affect the ABA-induced MAPK activation and ABA-enhanced antioxidant defense systems. These results clearly suggest that MAPK but not PTP is involved in the ABA-induced antioxidant defense, and a crosstalk between H2O2 production and MAPK activation plays a pivotal role in the ABA signaling. ABA-induced H2O2 production activates MAPK, which, in turn, induces the expression and the activities of antioxidant enzymes. The activation of MAPK also enhances the H2O2 production, forming a positive feedback loop.
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