title: Abscisic Acid-Cytokinin Antagonism Modulates Resistance Against Pseudomonas syringae in Tobacco.
abstract: Phytohormones are known as essential regulators of plant defenses, with ethylene, jasmonic acid, and salicylic acid as the central immunity backbone, while other phytohormones have been demonstrated to interact with this. Only recently, a function of the classic phytohormone cytokinin in plant immunity has been described in Arabidopsis, rice, and tobacco. Although interactions of cytokinins with salicylic acid and auxin have been indicated, the complete network of cytokinin interactions with other immunity-relevant phytohormones is not yet understood. Therefore, we studied the interaction of kinetin and abscisic acid as a negative regulator of plant immunity to modulate resistance in tobacco against Pseudomonas syringae. By analyzing infection symptoms, pathogen proliferation, and accumulation of the phytoalexin scopoletin as a key mediator of kinetin-induced resistance in tobacco, antagonistic interaction of these phytohormones in plant immunity was identified. Kinetin reduced abscisic acid levels in tobacco, while increased abscisic acid levels by exogenous application or inhibition of abscisic acid catabolism by diniconazole neutralized kinetin-induced resistance. Based on these results, we conclude that reduction of abscisic acid levels by enhanced abscisic acid catabolism strongly contributes to cytokinin-mediated resistance effects. Thus, the identified cytokinin-abscisic acid antagonism is a novel regulatory mechanism in plant immunity.
authors.forename: Dominik K
authors.initials: DK
authors.lastname: Großkinsky
authors.forename: Eric
authors.initials: E
authors.lastname: van der Graaff
authors.forename: Thomas
authors.initials: T
authors.lastname: Roitsch
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D054884:Host-Pathogen Interactions; D007210:Indoleacetic Acids / Q000378:metabolism; D054883:Oxylipins / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D010937:Plant Growth Regulators / Q000378:metabolism*; D057865:Plant Immunity; D018515:Plant Leaves / Q000276:immunology / Q000382:microbiology; D044224:Pseudomonas syringae / Q000502:physiology*; D020156:Salicylic Acid / Q000378:metabolism; D014026:Nicotiana / Q000276:immunology* / Q000382:microbiology
chemical_list: D003517:Cyclopentanes; D003583:Cytokinins; D005030:Ethylenes; D007210:Indoleacetic Acids; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid; D000040:Abscisic Acid; C036216:ethylene; D020156:Salicylic Acid
keywords: Nicotiana tabacum; plant–pathogen interaction