Comprehensive Analysis of Organic Ligands in Whole Root Exudates Using Nuclear Magnetic Resonance and Gas Chromatography–Mass Spectrometry

Root exudates in the rhizosphere are vital to the normal life cycle of plants. A key factor is phytometallophores, which function in the nutritional acquisition of iron and zinc and are likely to be important in the uptake of pollutant metals by plants. Unraveling the biochemistry of these compounds...

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Bibliographic Details
Published in:	Analytical biochemistry Vol. 251; no. 1; pp. 57 - 68
Main Authors:	Fan, Teresa W.-M., Lane, Andrew N., Pedler, Judy, Crowley, David, Higashi, Richard M.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 15-08-1997 Academic Press
Subjects:	CHEMISTRY ENVIRONMENTAL SCIENCES Gas Chromatography-Mass Spectrometry - methods Hordeum - chemistry INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY Ligands Magnetic Resonance Spectroscopy - methods Metals - analysis NUCLEAR MAGNETIC RESONANCE Plant Roots - chemistry Siderophores - analysis SPECTROSCOPY
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Summary:	Root exudates in the rhizosphere are vital to the normal life cycle of plants. A key factor is phytometallophores, which function in the nutritional acquisition of iron and zinc and are likely to be important in the uptake of pollutant metals by plants. Unraveling the biochemistry of these compounds is tedious using traditional analyses, which also fall short in providing the overall chemical composition or in detecting unknown or unexpected organic ligands in the exudates. Here, we demonstrate a comprehensive analysis of the exudate composition directly by1H and13C multidimensional NMR and silylation GC–MS. The advantages are (a) minimal sample preparation, with no loss of unknown compounds, and reduced net analysis time; (b) structure-based analysis for universal detection and identification; and (c) simultaneous analysis of a large number of constituents in a complex mixture. Using barley root exudates, a large number of common organic and amino acids were identified. Three derivatives of mugineic acid phytosiderophores were also determined, the major one being 3-epihydroxymugineic acid, for which complete1H and13C NMR assignments were obtained. Quantification of all major components using these methods revealed a sevenfold increase in total exudation under moderate iron deficiency, with 3-epihydroxymugineic acid comprising approximately 22% of the exudate mixture. As iron deficiency increased, total quantities of exudate per gram of root remained unchanged, but the relative quantity of carbon allocated to phytosiderophore increased to approximately 50% of the total exudate in response to severe iron deficiency.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 USDOE Office of Environmental Management (EM)
ISSN:	0003-2697 1096-0309
DOI:	10.1006/abio.1997.2235