title: Epoxycarotenoid cleavage by NCED5 fine-tunes ABA accumulation and affects seed dormancy and drought tolerance with other NCED family members.
abstract: Carotenoid cleavage, catalyzed by the 9-cis-epoxycarotenoid dioxygenase (NCED) constitutes a key step in the regulation of ABA biosynthesis. In Arabidopsis, this enzyme is encoded by five genes. NCED3 has been shown to play a major role in the regulation of ABA synthesis in response to water deficit, whereas NCED6 and NCED9 have been shown to be essential for the ABA production in the embryo and endosperm that imposes dormancy. Reporter gene analysis was carried out to determine the spatiotemporal pattern of NCED5 and NCED9 gene expression. GUS activity from the NCED5 promoter was detected in both the embryo and endosperm of developing seeds with maximal staining after mid-development. NCED9 expression was found at early stages in the testa outer integument layer 1, and after mid-development in epidermal cells of the embryo, but not in the endosperm. In accordance with its temporal- and tissue-specific expression, the phenotypic analysis of nced5 nced6 nced9 triple mutant showed the involvement of the NCED5 gene, together with NCED6 and NCED9, in the induction of seed dormancy. In contrast to nced6 and nced9, however, nced5 mutation did not affect the gibberellin required for germination. In vegetative tissues, combining nced5 and nced3 mutations reduced vegetative growth, increased water loss upon dehydration, and decreased ABA levels under both normal and stressed conditions, as compared with nced3. NCED5 thus contributes, together with NCED3, to ABA production affecting plant growth and water stress tolerance.
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, AgroParisTech, F-78026 Versailles Cedex, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Frey
authors.forename: Delphine
authors.initials: D
authors.lastname: Effroy
authors.forename: Valérie
authors.initials: V
authors.lastname: Lefebvre
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Seo
authors.forename: François
authors.initials: F
authors.lastname: Perreau
authors.forename: Adeline
authors.initials: A
authors.lastname: Berger
authors.forename: Julien
authors.initials: J
authors.lastname: Sechet
authors.forename: Alexandra
authors.initials: A
authors.lastname: To
authors.forename: Helen M
authors.initials: HM
authors.lastname: North
authors.forename: Annie
authors.initials: A
authors.lastname: Marion-Poll
mesh_terms: D000040:Abscisic Acid / Q000032:analysis / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D003681:Dehydration; D049308:Dioxygenases / Q000235:genetics* / Q000378:metabolism; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D017930:Genes, Reporter; D018525:Germination; D005875:Gibberellins / Q000378:metabolism; D009154:Mutation; D009928:Organ Specificity; D010641:Phenotype; D057445:Plant Dormancy; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D036226:Seedlings / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D014867:Water / Q000378:metabolism
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D014867:Water; D000040:Abscisic Acid; D049308:Dioxygenases; C109043:9-cis-epoxy-carotenoid dioxygenase