title: DAO1 catalyzes temporal and tissue-specific oxidative inactivation of auxin in Arabidopsis thaliana.
abstract: Tight homeostatic regulation of the phytohormone auxin [indole-3-acetic acid (IAA)] is essential to plant growth. Auxin biosynthetic pathways and the processes that inactivate auxin by conjugation to amino acids and sugars have been thoroughly characterized. However, the enzyme that catalyzes oxidation of IAA to its primary catabolite 2-oxindole-3-acetic acid (oxIAA) remains uncharacterized. Here, we show that DIOXYGENASE FOR AUXIN OXIDATION 1 (DAO1) catalyzes formation of oxIAA in vitro and in vivo and that this mechanism regulates auxin homeostasis and plant growth. Null dao1-1 mutants contain 95% less oxIAA compared with wild type, and complementation of dao1 restores wild-type oxIAA levels, indicating that DAO1 is the primary IAA oxidase in seedlings. Furthermore, dao1 loss of function plants have altered morphology, including larger cotyledons, increased lateral root density, delayed sepal opening, elongated pistils, and reduced fertility in the primary inflorescence stem. These phenotypes are tightly correlated with DAO1 spatiotemporal expression patterns as shown by DAO1pro:β-glucuronidase (GUS) activity and DAO1pro:YFP-DAO1 signals, and transformation with DAO1pro:YFP-DAO1 complemented the mutant phenotypes. The dominant dao1-2D mutant has increased oxIAA levels and decreased stature with shorter leaves and inflorescence stems, thus supporting DAO1 IAA oxidase function in vivo. A second isoform, DAO2, is very weakly expressed in seedling root apices. Together, these data confirm that IAA oxidation by DAO1 is the principal auxin catabolic process in Arabidopsis and that localized IAA oxidation plays a role in plant morphogenesis.
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742;
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691; Ohio Agricultural Research and Development Center Metabolite Analysis Cluster, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691;
authors.forename: Jinshan Ella
authors.initials: JE
authors.lastname: Lin
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742;
authors.forename: Chinchu
authors.initials: C
authors.lastname: Harris
authors.affiliation: Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742; Plant Protection and Animal Health, Forestry, Agronomy, Universidade Estadual de São Paulo, Sao Paulo, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Campos Mastrotti Pereira
authors.affiliation: Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742;
authors.forename: Fan
authors.initials: F
authors.lastname: Wu
authors.affiliation: Department of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691; Ohio Agricultural Research and Development Center Metabolite Analysis Cluster, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691;
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Blakeslee
authors.affiliation: Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742; Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742; wapeer@umd.edu.
authors.forename: Wendy Ann
authors.initials: WA
authors.lastname: Peer
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D004269:DNA, Bacterial / Q000235:genetics; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D005816:Genetic Complementation Test; D007210:Indoleacetic Acids / Q000378:metabolism*; D055442:Metabolome; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity; D010084:Oxidation-Reduction; D010641:Phenotype; D010802:Phylogeny; D018517:Plant Roots / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D053719:Tandem Mass Spectrometry; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D007210:Indoleacetic Acids; D012333:RNA, Messenger; D011994:Recombinant Proteins; C036483:T-DNA; C030737:indoleacetic acid
keywords: auxin homeostasis; auxin oxidase; auxin oxidation; flowers; lateral roots