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The tryptamine pathway is one of five proposed pathways for the biosynthesis of indole-3-acetic acid (IAA), the primary auxin in plants. The enzymes AtYUC1 (Arabidopsis thaliana), FZY (Solanum lycopersicum), and ZmYUC (Zea mays) are reported to catalyze the conversion of tryptamine to N-hydroxytryptamine, putatively a rate-limiting step of the tryptamine pathway for IAA biosynthesis. This conclusion was based on in vitro assays followed by mass spectrometry or HPLC analyses. However, there are major inconsistencies between the mass spectra reported for the reaction products. Here, we present mass spectral data for authentic N-hydroxytryptamine, 5-hydroxytryptamine (serotonin), and tryptamine to demonstrate that at least some of the published mass spectral data for the YUC in vitro product are not consistent with N-hydroxytryptamine. We also show that tryptamine is not metabolized to IAA in pea (Pisum sativum) seeds, even though a PsYUC-like gene is strongly expressed in these organs. Combining these findings, we propose that at present there is insufficient evidence to consider N-hydroxytryptamine an intermediate for IAA biosynthesis.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Horticultural crops
Objective Field:	Horticultural crops not elsewhere classified
UTAS Author:	Tivendale, ND (Mr Nathan Tivendale)
UTAS Author:	Davies, NW (Associate Professor Noel Davies)
UTAS Author:	Molesworth, PP (Dr Peter Molesworth)
UTAS Author:	Davidson, SE (Dr Sandra Davidson)
UTAS Author:	Smith, JA (Associate Professor Jason Smith)
UTAS Author:	Lowe, EK (Mr Edwin Lowe)
UTAS Author:	Reid, JB (Professor Jim Reid)
UTAS Author:	Ross, JJ (Associate Professor John Ross)
ID Code:	67348
Year Published:	2010
Web of Science® Times Cited:	50
Deposited By:	Plant Science
Deposited On:	2011-03-02
Last Modified:	2011-05-12
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