title: Cytokinin and auxin inhibit abscisic acid-induced stomatal closure by enhancing ethylene production in Arabidopsis.
abstract: Cytokinins and auxins are major phytohormones involved in various aspects of plant growth and development. These phytohormones are also known to antagonize the effects of abscisic acid (ABA) on stomatal movement, and to affect ethylene biosynthesis. As ethylene has an antagonistic effect on ABA-induced stomatal closure, the possibility that the antagonistic effects of these phytohormones on ABA were mediated through ethylene biosynthesis was investigated. Both the cytokinin, 6-benzyladenine (BA), and the auxin, 1-naphthaleneacetic acid (NAA), antagonized ABA-induced stomatal closure in a manner similar to that following application of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). However, these effects were negated when ethylene signalling, perception, or biosynthesis were blocked. As stomatal aperture is regulated by changes in guard cell volume, ABA application was found to reduce the volume of the guard cell protoplasts (GCP). It was found that BA, NAA, or ACC application compensated perfectly for the reduction in GCP volume by ABA application in WT plants. The above observations suggest that cytokinins and auxins inhibit ABA-induced stomatal closure through the modulation of ethylene biosynthesis, and that ethylene inhibits the ABA-induced reduction of osmotic pressure in the guard cells.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Toshio
authors.initials: T
authors.lastname: Sano
authors.forename: Masanori
authors.initials: M
authors.lastname: Tamaoki
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Nakajima
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kondo
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Hasezawa
mesh_terms: D000040:Abscisic Acid / Q000037:antagonists & inhibitors / Q000502:physiology*; D000598:Amino Acids, Cyclic; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D001593:Benzyl Compounds; D048429:Cell Size; D005030:Ethylenes / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007701:Kinetin; D009280:Naphthaleneacetic Acids; D019441:Plant Epidermis / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology; D011523:Protoplasts / Q000166:cytology / Q000502:physiology; D011687:Purines
chemical_list: D000598:Amino Acids, Cyclic; D001593:Benzyl Compounds; D005030:Ethylenes; D009280:Naphthaleneacetic Acids; D011687:Purines; C034182:1-naphthaleneacetic acid; C023863:1-aminocyclopropane-1-carboxylic acid; D000040:Abscisic Acid; C036216:ethylene; C480551:benzylaminopurine; D007701:Kinetin