title: The selectivity of 6-nor-ABA and 7'-nor-ABA for abscisic acid receptor subtypes.
abstract: Abscisic acid (ABA), a plant hormone, is involved in many plant development processes and environmental stress responses that are regulated by a Pyrabactin Resistant 1 (PYR)/Pyrabactin Resistant-Like (PYL)/Regulatory Component of ABA Receptor (RCAR) receptor protein-mediated signal transduction pathway. In Arabidopsis thaliana, PYL proteins constitute a 14-member family comprising two distinct subclasses: dimeric receptors (PYR1 and PYL1-PYL3) and monomeric receptors (PYL4-PYL13). The individual contributions of PYL subclasses/subtypes with specific physiological actions are still poorly understood; consequently, the development of PYL subclass/subtype-selective agonists should be useful to reveal the different functions of these receptors. In this study, we focused on the ABA analogs 6-nor-ABA and 7'-nor-ABA, which were expected to function as monomeric receptor-selective agonists on the basis of crystal structures of PYL-ABA complexes and sequence alignments of PYL subtypes. In a protein phosphatase 2C (PP2C) assay, the agonist activities of both analogs were lower than those of ABA toward all tested PYL proteins, regardless of subclass/subtype. Nevertheless, we found that 6-nor-ABA acts as a selective agonist at the physiological level: it induced stomatal closure but did not inhibit seed germination and root growth. On the basis of observed inhibitory activity against PP2C among different PYL subtypes, this biological effect of 6-nor-ABA may be attributed to the activity of that agonist on PYL5 and/or PYL6.
authors.affiliation: Graduate School of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Takeuchi
authors.affiliation: Graduate School of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan; Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ohnishi
authors.affiliation: Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Okamoto
authors.affiliation: Graduate School of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan; Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan; Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan. Electronic address: todoroki.yasushi@shizuoka.ac.jp.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Todoroki
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry*; D017360:Arabidopsis / Q000737:chemistry* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D018517:Plant Roots
chemical_list: D029681:Arabidopsis Proteins; D000040:Abscisic Acid
keywords: Abscisic acid; Agonist; PYR/PYL/RCAR receptor