title: Epoxycarotenoid-mediated synthesis of abscisic acid in Physcomitrella patens implicating conserved mechanisms for acclimation to hyperosmosis in embryophytes.
abstract: Plants acclimate to environmental stress signals such as cold, drought and hypersalinity, and provoke internal protective mechanisms. Abscisic acid (ABA), a carotenoid-derived phytohormone, which increases in response to the stress signals above, has been suggested to play a key role in the acclimation process in angiosperms, but the role of ABA in basal land plants such as mosses, including its biosynthetic pathways, has not been clarified. Targeted gene disruption of PpABA1, encoding zeaxanthin epoxidase in the moss Physcomitrella patens was conducted to determine the role of endogenous ABA in acclimation processes in mosses. The generated ppaba1 plants were found to accumulate only a small amount of endogenous ABA. The ppaba1 plants showed reduced osmotic acclimation capacity in correlation with reduced dehydration tolerance and accumulation of late embryogenesis abundant proteins. By contrast, cold-induced freezing tolerance was less affected in ppaba1, indicating that endogenous ABA does not play a major role in the regulation of cold acclimation in the moss. Our results suggest that the mechanisms for osmotic acclimation mediated by carotenoid-derived synthesis of ABA are conserved in embryophytes and that acquisition of the mechanisms played a crucial role in terrestrial adaptation and colonization by land plant ancestors.
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama, 338-8570, Japan.|Institute for Environmental Science and Technology, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takezawa
authors.affiliation: Department of BioScience, Tokyo University of Agriculture, 1-1-1, Sakuragaoka, Setagaya-ku, Tokyo, 156-8502, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Watanabe
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Totan Kumar
authors.initials: TK
authors.lastname: Ghosh
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Saruhashi
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Shimo-Okubo 255, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Experimental Plant Division, RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, 305-0074, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Ishiyama
authors.affiliation: Department of BioScience, Tokyo University of Agriculture, 1-1-1, Sakuragaoka, Setagaya-ku, Tokyo, 156-8502, Japan.
authors.forename: Shinnosuke
authors.initials: S
authors.lastname: Somemiya
authors.affiliation: Experimental Plant Division, RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, 305-0074, Japan.
authors.forename: Masatomo
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of BioScience, Tokyo University of Agriculture, 1-1-1, Sakuragaoka, Setagaya-ku, Tokyo, 156-8502, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sakata
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D019068:Bryopsida / Q000235:genetics / Q000502:physiology*; D002338:Carotenoids / Q000378:metabolism*; D005615:Freezing; D018506:Gene Expression Regulation, Plant; D009995:Osmosis; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological
chemical_list: D010937:Plant Growth Regulators; D010940:Plant Proteins; D002338:Carotenoids; D000040:Abscisic Acid; D010088:Oxidoreductases; C097153:zeaxanthin epoxidase
keywords: Physcomitrella patens; abscisic acid (ABA); dehydration tolerance; osmotic acclimation; zeaxanthin epoxidase