title: Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3.
abstract: The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the two Arabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and show growth defects consistent with partial auxin deficiency. Together with previous work on YUCCA, a flavin monooxygenase also implicated in IAOx production, and nitrilases that convert indole-3-acetonitrile to auxin, this work provides a framework for further dissecting auxin biosynthetic pathways and their regulation.
authors.affiliation: Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
authors.forename: Yunde
authors.initials: Y
authors.lastname: Zhao
authors.forename: Anna K
authors.initials: AK
authors.lastname: Hull
authors.forename: Neeru R
authors.initials: NR
authors.lastname: Gupta
authors.forename: Kendrick A
authors.initials: KA
authors.lastname: Goss
authors.forename: José
authors.initials: J
authors.lastname: Alonso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
authors.forename: Jennifer
authors.initials: J
authors.lastname: Normanly
authors.forename: Joanne
authors.initials: J
authors.lastname: Chory
authors.forename: John L
authors.initials: JL
authors.lastname: Celenza
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000096:biosynthesis* / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D009154:Mutation; D010091:Oximes / Q000378:metabolism; D010641:Phenotype; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D007211:Indoles; D010091:Oximes; C467098:indole-3-acetaldoxime; C030737:indoleacetic acid; D014364:Tryptophan; D003577:Cytochrome P-450 Enzyme System