title: The short-chain alcohol dehydrogenase ABA2 catalyzes the conversion of xanthoxin to abscisic aldehyde.
abstract: Mutants able to germinate and perform early growth in medium containing a high NaCl concentration were identified during the course of two independent screenings and named salt resistant (sre) and salobreño (sañ). The sre and sañ mutants also were able to germinate in high-osmoticum medium, indicating that they are osmotolerant in a germination assay. Complementation analyses revealed that sre1-1, sre1-2, sañ3-1, and sañ3-2 were alleles of the abscisic acid (ABA) biosynthesis ABA2 gene. A map-based cloning strategy allowed the identification of the ABA2 gene and molecular characterization of four new aba2 alleles. The ABA2 gene product belongs to the family of short-chain dehydrogenases/reductases, which are known to be NAD- or NADP-dependent oxidoreductases. Recombinant ABA2 protein produced in Escherichia coli exhibits a K(m) value for xanthoxin of 19 micro M and catalyzes in a NAD-dependent manner the conversion of xanthoxin to abscisic aldehyde, as determined by HPLC-mass spectrometry. The ABA2 mRNA is expressed constitutively in all plant organs examined and is not upregulated in response to osmotic stress. The results of this work are discussed in the context of previous genetic and biochemical evidence regarding ABA biosynthesis, confirming the xanthoxin-->abscisic aldehyde-->ABA transition as the last steps of the major ABA biosynthetic pathway.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, E-46022 Valencia, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: González-Guzmán
authors.forename: Nadezda
authors.initials: N
authors.lastname: Apostolova
authors.forename: José M
authors.initials: JM
authors.lastname: Bellés
authors.forename: José M
authors.initials: JM
authors.lastname: Barrero
authors.forename: Pedro
authors.initials: P
authors.lastname: Piqueras
authors.forename: María R
authors.initials: MR
authors.lastname: Ponce
authors.forename: José L
authors.initials: JL
authors.lastname: Micol
authors.forename: Ramón
authors.initials: R
authors.lastname: Serrano
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodríguez
mesh_terms: D000040:Abscisic Acid / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000494:pharmacology; D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002338:Carotenoids; D002384:Catalysis; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018525:Germination; D008353:Mannitol / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D009997:Osmotic Pressure / Q000187:drug effects; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012717:Sesquiterpenes / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D012717:Sesquiterpenes; C012475:xanthoxin; D002338:Carotenoids; D008353:Mannitol; D012965:Sodium Chloride; D000040:Abscisic Acid; C469255:ABA2 protein, Arabidopsis; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase; D000445:Aldehyde Oxidoreductases; C411385:abscisic acid-aldehyde oxidase