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Reassessing the role of N-Hydroxytryptamine in auxin biosynthesis

journal contribution
posted on 2023-05-17, 04:45 authored by Nathan TivendaleNathan Tivendale, Noel DaviesNoel Davies, Molesworth, PP, Davidson, SE, Jason SmithJason Smith, Lowe, EK, James ReidJames Reid, John RossJohn Ross
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.

History

Publication title

Plant Physiology

Volume

154

Issue

4

Pagination

1957-1965

ISSN

0032-0889

Department/School

School of Natural Sciences

Publisher

Amer Soc Plant Biologists

Place of publication

15501 Monona Drive, Rockville, USA, Md, 20855

Rights statement

Copyright © 2010 by the American Society of Plant Biologists

Repository Status

  • Restricted

Socio-economic Objectives

Horticultural crops not elsewhere classified

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