Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1998 Sep;118(1):285-96.
doi: 10.1104/pp.118.1.285.

Metabolism of indole-3-acetic acid in Arabidopsis

A Ostin  1 , M Kowalyczk, R P Bhalerao, G Sandberg
Affiliations

Metabolism of indole-3-acetic acid in Arabidopsis

A Ostin et al. Plant Physiol. 1998 Sep.

Abstract

The metabolism of indole-3-acetic acid (IAA) was investigated in 14-d-old Arabidopsis plants grown in liquid culture. After ruling out metabolites formed as an effect of nonsterile conditions, high-level feeding, and spontaneous interconversions, a simple metabolic pattern emerged. Oxindole-3-acetic acid (OxIAA), OxIAA conjugated to a hexose moiety via the carboxyl group, and the conjugates indole-3-acetyl aspartic acid (IAAsp) and indole-3-acetyl glutamate (IAGlu) were identified by mass spectrometry as primary products of IAA fed to the plants. Refeeding experiments demonstrated that none of these conjugates could be hydrolyzed back to IAA to any measurable extent at this developmental stage. IAAsp was further oxidized, especially when high levels of IAA were fed into the system, yielding OxIAAsp and OH-IAAsp. This contrasted with the metabolic fate of IAGlu, since that conjugate was not further metabolized. At IAA concentrations below 0.5 microM, most of the supplied IAA was metabolized via the OxIAA pathway, whereas only a minor portion was conjugated. However, increasing the IAA concentrations to 5 microM drastically altered the metabolic pattern, with marked induction of conjugation to IAAsp and IAGlu. This investigation used concentrations for feeding experiments that were near endogenous levels, showing that the metabolic pathways controlling the IAA pool size in Arabidopsis are limited and, therefore, make good targets for mutant screens provided that precautions are taken to avoid inducing artificial metabolism.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Gradient-elution reversed-phase HPLC-radioactivity chromatogram of partially purified extracts of Arabidopsis plants fed [1-14C]IAA. All incubations were done in darkness.
Figure 2
Figure 2
Frit-FAB-MS spectra of metabolite 1 (A); and GC-MS spectrum of silylated metabolite 1 (B) and of the silylated hydrolysis product of metabolite 1 (C).
Figure 3
Figure 3
Time-course study of a [1-14C]IAA feed to Arabidopsis plants grown in liquid culture for 2 to 120 h and of partially purified extracts spiked with [14C]OxIAA and [14C]IAAsp.
Figure 4
Figure 4
Time-course study of [1-14C]IAAsp (A), [1-14C]IAGlu (B), and [1-14C]OxIAA (C) feeds to Arabidopsis plants grown in liquid culture for 6, 12, and 48 h.
Figure 5
Figure 5
Gradient-elution reversed-phase HPLC-radioactivity chromatogram of aliquots of partially purified extracts of sterile-grown plants fed [5-3H]IAA in liquid culture in darkness for 6 to 48 h.
Figure 6
Figure 6
Proposed metabolic pathway for IAA in Arabidopsis plants. The solid arrows represent the steps that have been demonstrated by in planta conversions under physiologically relevant conditions.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Andersson B, Sandberg G. Identification of endogenous N-(3-indoleacetyl)aspartic acid in Scots pine (Pinus sylvestris L.) by combined gas chromatography-mass spectrometry, using high-performance liquid chromatography for quantification. J Chromatogr. 1982;238:151–156.
    1. Bandurski RS, Schulze A. Concentrations of indole-3-acetic acid and its esters in Avena and Zea. Plant Physiol. 1974;54:257–262. - PMC - PubMed
    1. Bartel B, Fink GR. ILR1, an amidohydrolase that releases active indole-3-acetic acid from conjugates. Science. 1995;268:1745–1748. - PubMed
    1. Bennett JM, Marchant A, Green HG, May ST, Ward SP, Millner PA, Walker AR, Schultz B, Feldmann KA. Arabidopsis AUX 1 gene, a permease-like regulator of root gravitropism. Science. 1996;273:948–950. - PubMed
    1. Bialek K, Cohen JD. Free and conjugated indole-3-acetic acid in developing bean seeds. Plant Physiol. 1989;91:775–779. - PMC - PubMed

Publication types

MeSH terms

LinkOut - more resources