Tuominen H, Ostin A, Sandberg G, Sundberg B
A Novel Metabolic Pathway for Indole- 3- Acetic- Acid in Apical Shoots of Populus- Tremula (L) X Populus-Tremuloides (Michx)
Plant Physiology: 1994 106:1511-1520
Metabolism of indole-3-acetic acid (IAA) in apical shoots of Populus tremula (L.) x Populus tremuloides (Michx.) was investigated by feeding a mixture of [C-12]IAA, [C-13(6)]IAA, and [1'-C-14]IAA through the base of the excised stem. HPLC of methanolic plant extracts revealed eight major radiolabeled metabolites after a 24-h incubation period. Comparison between feeds with [5-H-3]IAA and [1'-C-14]IAA showed that all detectable metabolites were nondecarboxylative products. The purified radiolabeled HPLC fractions were screened by frit-fast atom bombardment liquid chromatography-mass spectrometry for compounds with characteristic fragment pairs originating from the application with C-12 and C-13 isotopes. Samples of interest were further characterized by gas chromatography-mass spectrometry. Using this procedure, oxindole-3-acetic acid (OxIAA), indole-3-acetyl-N-aspartic acid (IAAsp), oxindole-3-acetyl-N-aspartic acid (OxIAAsp), and ring-hydroxylated oxindole-3-acetic acid were all identified as IAA metabolites. Furthermore, a novel metabolic pathway from IAA via IAAsp and OxIAAsp to OxIAA was established on the basis of refeeding experiments with the different IAA metabolites.
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