title: ZmMPK5 is required for the NADPH oxidase-mediated self-propagation of apoplastic H2O2 in brassinosteroid-induced antioxidant defence in leaves of maize.
abstract: Brassinosteroids (BRs) have been shown to induce hydrogen peroxide (H(2)O(2)) accumulation, and BR-induced H(2)O(2) up-regulates antioxidant defence systems in plants. However, the mechanisms by which BR-induced H(2)O(2) regulates antioxidant defence systems in plants remain to be determined. In the present study, the role of ZmMPK5, a mitogen-activated protein kinase, in BR-induced anitioxidant defence and the relationship between the activation of ZmMPK5 and H(2)O(2) production in BR signalling were investigated in leaves of maize (Zea mays) plants. BR treatment activated ZmMPK5, induced apoplastic and chloroplastic H(2)O(2) accumulation, and enhanced the total activities of antioxidant enzymes. Such enhancements were blocked by pre-treatment with mitogen-activated protein kinase kinase (MAPKK) inhibitors and H(2)O(2) inhibitors or scavengers. Pre-treatment with MAPKK inhibitors substantially arrested the BR-induced apoplastic H(2)O(2) production after 6 h of BR treatment, but did not affect the levels of apoplastic H(2)O(2) within 1 h of BR treatment. BR-induced gene expression of NADPH oxidase was also blocked by pre-treatment with MAPKK inhibitors and an apoplastic H(2)O(2) inhibitor or scavenger after 120 min of BR treatment, but was not affected within 30 min of BR treatment. These results suggest that the BR-induced initial apoplastic H(2)O(2) production activates ZmMPK5, which is involved in self-propagation of apoplastic H(2)O(2) via regulation of NADPH oxidase gene expression in BR-induced antioxidant defence systems.
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Aying
authors.initials: A
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Nenghui
authors.initials: N
authors.lastname: Ye
authors.forename: Jianmei
authors.initials: J
authors.lastname: Cao
authors.forename: Mingpu
authors.initials: M
authors.lastname: Tan
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Mingyi
authors.initials: M
authors.lastname: Jiang
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D060406:Brassinosteroids; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002777:Cholestanols / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000648:ultrastructure; D010940:Plant Proteins; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects; D003313:Zea mays / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000276:immunology
chemical_list: D000975:Antioxidants; D060406:Brassinosteroids; D002777:Cholestanols; D016166:Free Radical Scavengers; D010940:Plant Proteins; D047428:Protein Kinase Inhibitors; D013260:Steroids, Heterocyclic; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D020928:Mitogen-Activated Protein Kinases; C402117:ZmMPK5; C023623:brassinolide