title: Tryptophan-dependent indole-3-acetic acid biosynthesis by 'IAA-synthase' proceeds via indole-3-acetamide.
abstract: Plants are suggested to produce their major growth promoting phytohormone, indole-3-acetic acid (IAA), via multiple redundantly operating pathways. Although great effort has been made and plenty of possible routes have been proposed based on experimental evidence, a complete pathway for IAA production has yet to be demonstrated. In this study, an in-vitro approach was taken to examine the conversion of l-tryptophan (l-trp) to IAA by gas chromatography-mass spectrometry (GC-MS). Especially the influence of putative reaction intermediates on the enzymatic conversion of l-trp to IAA was analyzed. Among the substances tested only indole-3-acetamide (IAM) showed a pronounced effect on the l-trp conversion. We additionally report that IAM is synthesized from l-trp and that it is further converted to IAA by the utilized cell free Arabidopsis extract. Together, our results underscore the functionality of an IAM-dependent auxin biosynthesis pathway in Arabidopsis thaliana.
authors.affiliation: Department of Plant Physiology, Ruhr-University Bochum, Universitätsstrasse 150, 44801 Bochum, Germany. Stephan.Pollmann@rub.de
authors.forename: Stephan
authors.initials: S
authors.lastname: Pollmann
authors.forename: Petra
authors.initials: P
authors.lastname: Düchting
authors.forename: Elmar W
authors.initials: EW
authors.lastname: Weiler
mesh_terms: D000581:Amidohydrolases / Q000502:physiology; D000619:Aminohydrolases / Q000235:genetics; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D014363:Tryptamines / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D014363:Tryptamines; C030820:tryptamine; C030737:indoleacetic acid; C015950:indoleacetamide; D014364:Tryptophan; D000581:Amidohydrolases; C019665:amidase; D000619:Aminohydrolases; C021867:nitrilase