Three oxidative metabolites of indole-3-acetic acid from Arabidopsis thaliana.
Three metabolites of indole-3-acetic acid (IAA), N-(6-hydroxyindol-3-ylacetyl)-phenylalanine (6-OH-IAA-Phe), N-(6-hydroxyindol-3-ylacetyl)-valine (6-OH-IAA-Val), and 1-O-(2-oxoindol-3-ylacetyl)-beta-d-glucopyranose (OxIAA-Glc), were found by a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS)-based search for oxidative IAA metabolites during the vegetative growth of Arabidopsis. Their structures were confirmed by making a comparison of chromatographic characteristics and mass spectra between naturally occurring compounds and synthetic standards. An incorporation study using deuterium-labeled compounds showed that 6-OH-IAA-Phe and 6-OH-IAA-Val were biosynthesized from IAA-Phe and IAA-Val, respectively, which strongly suggested the formation of these amino acid conjugates of IAA in plants. Both 6-OH-IAA-Phe and 6-OH-IAA-Val were inactive as auxins, as indicated by no significant root growth inhibition in Arabidopsis. Quantitative analysis demonstrated that OxIAA-Glc was present in the largest amount among the metabolites of IAA in Arabidopsis, suggesting that the conversion into OxIAA-Glc represents the main metabolic process regarding IAA in Arabidopsis.
Kai
Kenji
K
Division of Applied Life Science, Graduate School of Agriculture, Kitashirakawa, Kyoto University, Kyoto 606-8502, Japan.
Horita
Junko
J
Wakasa
Kyo
K
Miyagawa
Hisashi
H
D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D002853:Chromatography, Liquid; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006900:Hydroxylation; D007210:Indoleacetic Acids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014633:Valine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
C523337:1-O-(2-oxoindol-3-ylacetyl)-beta-D-glucopyranose; D005960:Glucosides; D007210:Indoleacetic Acids; C523336:N-(6-hydroxyindol-3-ylacetyl)-phenylalanine; C523338:N-(6-hydroxyindol-3-ylacetyl)-valine; D010649:Phenylalanine; C030737:indoleacetic acid; D014633:Valine