Reactive Oxygen Species Are Involved in Brassinosteroid-Induced Stress Tolerance in Cucumber

• Published in: Plant physiology (Bethesda) Vol. 150; no. 2; pp. 801 - 814
• Main Authors: Xia, Xiao-Jian, Wang, Yan-Jie, Zhou, Yan-Hong, Tao, Yuan, Mao, Wei-Hua, Shi, Kai, Asami, Tadao, Chen, Zhixiang, Yu, Jing-Quan
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.06.2009
• Subjects: Adaptation, Physiological; Adaptation, Physiological - drug effects; Antioxidants; Antioxidants - metabolism; Biological and medical sciences; Brassinosteroids; Cholestanols; Cholestanols - pharmacology; cold stress; Cold Temperature; cold tolerance; Cucumber mosaic virus; Cucumbers; Cucumis sativus; Cucumis sativus - drug effects; Cucumis sativus - genetics; Cucumis sativus - physiology; Cucumis sativus - virology; Cucumovirus; Cucumovirus - drug effects; Cucumovirus - physiology; drug effects; Environmental Stress and Adaptation to Stress; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Plant; Gene Expression Regulation, Plant - drug effects; Genes; genetics; Hydrogen Peroxide; Hydrogen Peroxide - metabolism; Kinetics; Leaves; metabolism; Models, Biological; Molecular Sequence Data; NADP (coenzyme); Oxidases; Oxidative stress; Paraquat; Paraquat - pharmacology; pharmacology; physiology; Plant physiology and development; Plants; reactive oxygen species; Reactive Oxygen Species - metabolism; regulator genes; RNA, Messenger; RNA, Messenger - genetics; RNA, Messenger - metabolism; Seedlings; Steroids, Heterocyclic; Steroids, Heterocyclic - pharmacology; Stress tolerance; Stress, Physiological; Stress, Physiological - drug effects; Time Factors; virology; Brassinosteroid; Reactive oxygen species; Vegetable crop; Plant physiology; Dicotyledones; Angiospermae; Cucurbitaceae; Tolerance; Spermatophyta; Cucumis sativus; Cucumber; Stress
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.109.138230

Brassinosteroids (BRs) induce plant tolerance to a wide spectrum of stresses. To study how BR induces stress tolerance, we manipulated the BR levels in cucumber (Cucumis sativus) through a chemical genetics approach and found that BR levels were positively correlated with the tolerance to photo-oxidative and cold stresses and resistance to Cucumber mosaic virus. We also showed that BR treatment enhanced NADPH oxidase activity and elevated H₂O₂ levels in apoplast. H₂O₂ levels were elevated as early as 3 h and returned to basal levels 3 d after BR treatment. BR-induced H₂O₂ accumulation was accompanied by increased tolerance to oxidative stress. Inhibition of NADPH oxidase and chemical scavenging of H₂O₂ reduced BR-induced oxidative and cold tolerance and defense gene expression. BR treatment induced expression of both regulatory genes, such as RBOH, MAPK1, and MAPK3, and genes involved in defense and antioxidant responses. These results strongly suggest that elevated H₂O₂ levels resulting from enhanced NADPH oxidase activity are involved in the BR-induced stress tolerance.