title: Positive feedback regulation of maize NADPH oxidase by mitogen-activated protein kinase cascade in abscisic acid signalling.
abstract: In maize (Zea mays), abscisic acid (ABA)-induced H(2)O(2) production activates a 46 kDa mitogen-activated protein kinase (p46MAPK), and the activation of p46MAPK also regulates the production of H(2)O(2). However, the mechanism for the regulation of H(2)O(2) production by MAPK in ABA signalling remains to be elucidated. In this study, four reactive oxygen species (ROS)-producing NADPH oxidase (rboh) genes (ZmrbohA-D) were isolated and characterized in maize leaves. ABA treatment induced a biphasic response (phase I and phase II) in the expression of ZmrbohA-D and the activity of NADPH oxidase. Phase II induced by ABA was blocked by pretreatments with two MAPK kinase (MPKKK) inhibitors and two H(2)O(2) scavengers, but phase I was not affected by these inhibitors or scavengers. Treatment with H(2)O(2) alone also only induced phase II, and the induction was arrested by the MAPKK inhibitors. Furthermore, the ABA-activated p46MAPK was partially purified. Using primers corresponding to the sequences of internal tryptic peptides, the p46MAPK gene was cloned. Analysis of the tryptic peptides and the p46MAPK sequence indicate it is the known ZmMPK5. Treatments with ABA and H(2)O(2) led to a significant increase in the activity of ZmMPK5, although ABA treatment only induced a slight increase in the expression of ZmMPK5. The data indicate that H(2)O(2)-activated ZmMPK5 is involved in the activation of phase II in ABA signalling, but not in phase I. The results suggest that there is a positive feedback loop involving NADPH oxidase, H(2)O(2), and ZmMPK5 in ABA signalling.
authors: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
authors: Fan
authors: F
authors: Lin
authors: Haidong
authors: H
authors: Ding
authors: Jinxiang
authors: J
authors: Wang
authors: Hong
authors: H
authors: Zhang
authors: Aying
authors: A
authors: Zhang
authors: Yun
authors: Y
authors: Zhang
authors: Mingpu
authors: M
authors: Tan
authors: Wen
authors: W
authors: Dong
authors: Mingyi
authors: M
authors: Jiang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000595:Amino Acid Sequence; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019255:NADPH Oxidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction; D003313:Zea mays / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases