title: The Arabidopsis cytochrome P450 CYP707A encodes ABA 8'-hydroxylases: key enzymes in ABA catabolism.
abstract: The hormonal action of abscisic acid (ABA) in plants is controlled by the precise balance between its biosynthesis and catabolism. In plants, ABA 8'-hydroxylation is thought to play a predominant role in ABA catabolism. ABA 8'-hydroxylase was shown to be a cytochrome P450 (P450); however, its corresponding gene had not been identified. Through phylogenetic and DNA microarray analyses during seed imbibition, the candidate genes for this enzyme were narrowed down from 272 Arabidopsis P450 genes. These candidate genes were functionally expressed in yeast to reveal that members of the CYP707A family, CYP707A1-CYP707A4, encode ABA 8'-hydroxylases. Expression analyses revealed that CYP707A2 is responsible for the rapid decrease in ABA level during seed imbibition. During drought stress conditions, all CYP707A genes were upregulated, and upon rehydration a significant increase in mRNA level was observed. Consistent with the expression analyses, cyp707a2 mutants exhibited hyperdormancy in seeds and accumulated six-fold greater ABA content than wild type. These results demonstrate that CYP707A family genes play a major regulatory role in controlling the level of ABA in plants.
authors.affiliation: Plant Science Center, RIKEN, Yokohama, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kushiro
authors.forename: Masanori
authors.initials: M
authors.lastname: Okamoto
authors.forename: Kazumi
authors.initials: K
authors.lastname: Nakabayashi
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Yamagishi
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kitamura
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hirai
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Koshiba
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Eiji
authors.initials: E
authors.lastname: Nambara
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D015394:Molecular Structure; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010940:Plant Proteins; D012639:Seeds / Q000201:enzymology
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C107203:abscisic acid 8'-hydroxylase