title: Indolic constituents and indole-3-acetic acid biosynthesis in the wild-type and a tryptophan auxotroph mutant of Arabidopsis thaliana.
abstract: The tryptophan auxotroph mutant trp3-1 of Arabidopsis thaliana (L.) Heynh., despite having reduced levels of L-tryptophan, accumulates the tryptophan-derived glucosinolate, glucobrassicin and, thus, does not appear to be tryptophan-limited. However, due to the block in tryptophan synthase, the mutant hyperaccumulates the precursor indole-3-glycerophosphate (up to 10 mg per g FW). Instability of indole-3-glycerophosphate leads to release of indole-3-acetic acid (IAA) from this metabolite during standard workup of samples for determination of conjugated IAA. The apparent increase in "conjugated IAA" in trp3-1 mutant plants can be traced back entirely to indole-3-glycerophosphate degradation. Thus, the levels of neither free IAA nor conjugated IAA increase detectably in the trp3-1 mutant compared to wild-type plants. Precursor-feeding experiments to shoots of sterile-grown wild-type plants using [2H]5-L-tryptophan have shown incorporation of label from this precursor into indole-3-acetonitrile and indole-3-acetic acid with very little isotope dilution. It is concluded that Arabidopsis thaliana shoots synthesize IAA from L-tryptophan and that the non-tryptophan pathway is probably an artifact.
authors.affiliation: Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität, Bochum, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Müller
authors.forename: E W
authors.initials: EW
authors.lastname: Weiler
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D005994:Glycerophosphates / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009587:Nitrogen Isotopes; D021241:Spectrometry, Mass, Electrospray Ionization; D014316:Tritium; D014364:Tryptophan / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000378:metabolism
chemical_list: D005994:Glycerophosphates; D007210:Indoleacetic Acids; D007211:Indoles; D009587:Nitrogen Isotopes; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; D014316:Tritium; C008117:indoleglycerol phosphate; C030737:indoleacetic acid; D014364:Tryptophan