title: Yucasin is a potent inhibitor of YUCCA, a key enzyme in auxin biosynthesis.
abstract: Indole-3-acetic acid (IAA), an auxin plant hormone, is biosynthesized from tryptophan. The indole-3-pyruvic acid (IPyA) pathway, involving the tryptophan aminotransferase TAA1 and YUCCA (YUC) enzymes, was recently found to be a major IAA biosynthetic pathway in Arabidopsis. TAA1 catalyzes the conversion of tryptophan to IPyA, and YUC produces IAA from IPyA. Using a chemical biology approach with maize coleoptiles, we identified 5-(4-chlorophenyl)-4H-1,2,4-triazole-3-thiol (yucasin) as a potent inhibitor of IAA biosynthesis in YUC-expressing coleoptile tips. Enzymatic analysis of recombinant AtYUC1-His suggested that yucasin strongly inhibited YUC1-His activity against the substrate IPyA in a competitive manner. Phenotypic analysis of Arabidopsis YUC1 over-expression lines (35S::YUC1) demonstrated that yucasin acts in IAA biosynthesis catalyzed by YUC. In addition, 35S::YUC1 seedlings showed resistance to yucasin in terms of root growth. A loss-of-function mutant of TAA1, sav3-2, was hypersensitive to yucasin in terms of root growth and hypocotyl elongation of etiolated seedlings. Yucasin combined with the TAA1 inhibitor l-kynurenine acted additively in Arabidopsis seedlings, producing a phenotype similar to yucasin-treated sav3-2 seedlings, indicating the importance of IAA biosynthesis via the IPyA pathway in root growth and leaf vascular development. The present study showed that yucasin is a potent inhibitor of YUC enzymes that offers an effective tool for analyzing the contribution of IAA biosynthesis via the IPyA pathway to plant development and physiological processes.
authors.affiliation: Department of Biological Sciences, Tokyo Metropolitan University, Hachioji-shi, Tokyo, 192-0397, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Hayashi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Atsuko
authors.initials: A
authors.lastname: Gyohda
authors.forename: Chihiro
authors.initials: C
authors.lastname: Takaoka
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sakaguchi
authors.forename: Sachiko
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kasahara
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakai
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Kato
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Koshiba
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D053898:Biosynthetic Pathways; D018548:Cotyledon / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D004305:Dose-Response Relationship, Drug; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000737:chemistry / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism; D009154:Mutation; D010105:Oxygenases / Q000037:antagonists & inhibitors* / Q000235:genetics; D010641:Phenotype; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D018520:Plant Shoots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D054852:Small Molecule Libraries; D014230:Triazoles / Q000737:chemistry / Q000494:pharmacology*; D051279:Tryptophan Transaminase / Q000037:antagonists & inhibitors / Q000235:genetics; D003313:Zea mays / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development
chemical_list: C000591693:5-(4-chlorophenyl)-4H-1,2,4-triazole-3-thiol; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; D054852:Small Molecule Libraries; D014230:Triazoles; C008122:indol-3-yl pyruvic acid; C030737:indoleacetic acid; D010105:Oxygenases; C422746:YUC protein, Arabidopsis; D051279:Tryptophan Transaminase
keywords: Arabidopsis; IAA biosynthesis inhibitor; TAA; YUCCA; indole acetic acid; maize coleoptiles