Yucasin is a potent inhibitor of YUCCA, a key enzyme in auxin biosynthesis

Plant J. 2014 Feb;77(3):352-66. doi: 10.1111/tpj.12399. Epub 2014 Jan 16.

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.

Keywords: Arabidopsis; IAA biosynthesis inhibitor; TAA; YUCCA; indole acetic acid; maize coleoptiles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / drug effects*
  • Arabidopsis / enzymology
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / antagonists & inhibitors*
  • Arabidopsis Proteins / genetics
  • Biosynthetic Pathways
  • Cotyledon / drug effects
  • Cotyledon / enzymology
  • Cotyledon / genetics
  • Cotyledon / growth & development
  • Dose-Response Relationship, Drug
  • Gene Expression Regulation, Plant
  • Indoleacetic Acids / chemistry
  • Indoleacetic Acids / metabolism*
  • Indoles / metabolism
  • Mutation
  • Oxygenases / antagonists & inhibitors*
  • Oxygenases / genetics
  • Phenotype
  • Plant Growth Regulators / chemistry
  • Plant Growth Regulators / metabolism*
  • Plant Leaves / drug effects
  • Plant Leaves / enzymology
  • Plant Leaves / genetics
  • Plant Leaves / growth & development
  • Plant Roots / drug effects
  • Plant Roots / enzymology
  • Plant Roots / genetics
  • Plant Shoots / drug effects
  • Plant Shoots / enzymology
  • Plant Shoots / genetics
  • Plant Shoots / growth & development
  • Plants, Genetically Modified
  • Recombinant Fusion Proteins
  • Seedlings / drug effects
  • Seedlings / enzymology
  • Seedlings / genetics
  • Seedlings / growth & development
  • Small Molecule Libraries
  • Triazoles / chemistry
  • Triazoles / pharmacology*
  • Tryptophan Transaminase / antagonists & inhibitors
  • Tryptophan Transaminase / genetics
  • Zea mays / drug effects*
  • Zea mays / enzymology
  • Zea mays / genetics
  • Zea mays / growth & development

Substances

  • 5-(4-chlorophenyl)-4H-1,2,4-triazole-3-thiol
  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Indoles
  • Plant Growth Regulators
  • Recombinant Fusion Proteins
  • Small Molecule Libraries
  • Triazoles
  • indol-3-yl pyruvic acid
  • indoleacetic acid
  • Oxygenases
  • YUC protein, Arabidopsis
  • Tryptophan Transaminase