title: CYP707A3, a major ABA 8'-hydroxylase involved in dehydration and rehydration response in Arabidopsis thaliana.
abstract: Abscisic acid (ABA) catabolism is one of the determinants of endogenous ABA levels affecting numerous aspects of plant growth and abiotic stress responses. The major ABA catabolic pathway is triggered by ABA 8'-hydroxylation catalysed by the cytochrome P450 CYP707A family. Among four members of Arabidopsis CYP707As, the expression of CYP707A3 was most highly induced in response to both dehydration and subsequent rehydration. A T-DNA insertional cyp707a3-1 mutant contained higher ABA levels in turgid plants, which showed a reduced transpiration rate and hypersensitivity to exogenous ABA during early seedling growth. On dehydration, the cyp707a3-1 mutant accumulated a higher amount of stress-induced ABA than the wild type, an event that occurred relatively later and was coincident with slow drought induction of CYP707A3. The cyp707a3 mutant plants exhibited both exaggerated ABA-inducible gene expression and enhanced drought tolerance. Conversely, constitutive expression of CYP707A3 relieved growth retardation by ABA, increased transpiration, and a reduction of endogenous ABA in both turgid and dehydrated plants. Taken together, our results indicate that CYP707A3 plays an important role in determining threshold levels of ABA during dehydration and after rehydration.
authors.affiliation: Gene Discovery Research Group, RIKEN Plant Science Center, Yokohama, Kanagawa 230-0045, Japan.
authors.forename: Taishi
authors.initials: T
authors.lastname: Umezawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Okamoto
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kushiro
authors.forename: Eiji
authors.initials: E
authors.lastname: Nambara
authors.forename: Youko
authors.initials: Y
authors.lastname: Oono
authors.forename: Motoaki
authors.initials: M
authors.lastname: Seki
authors.forename: Masatomo
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Koshiba
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
mesh_terms: D000040:Abscisic Acid / Q000502:physiology; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D010940:Plant Proteins; D018749:RNA, Plant / Q000235:genetics / Q000302:isolation & purification; D015398:Signal Transduction; D014158:Transcription, Genetic; D014867:Water
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D014867:Water; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C107203:abscisic acid 8'-hydroxylase