title: De novo biosynthesis of defense root exudates in response to Fusarium attack in barley.
abstract: Summary *Despite recent advances in elucidation of natural products in root exudates, there are significant gaps in our understanding of the ecological significance of products in the rhizosphere. *Here, we investigated the potential of barley (Hordeum vulgare) to secrete defense root exudates when challenged by the soilborne pathogen Fusarium graminearum. *Liquid chromatography with photodiode array detection (LC-DAD) was used to profile induced small-molecular-weight exudates. Thus, t-cinnamic, p-coumaric, ferulic, syringic and vanillic acids were assigned to plant metabolism and were induced within 2 d after Fusarium inoculation. Biological tests demonstrated the ability of those induced root exudates to inhibit the germination of F. graminearum macroconidia. In vivo labeling experiments with (13)CO(2) revealed that the secreted t-cinnamic acid was synthesized de novo within 2 d of fungal infection. Simultaneously to its root exudation, t-cinnamic acid was accumulated in the roots. Microscopic analysis showed that nonlignin cell wall phenolics were induced not only in necrosed zones but in all root tissues. *Results suggest that barley plants under attack respond by de novo biosynthesis and secretion of compounds with antimicrobial functions that may mediate natural disease resistance.
authors.affiliation: ICG-3 Phytosphere, Forschungszentrum Jülich, D-52425 Jülich, Germany. arnaud.lanoue@univ-tours.fr
authors.forename: Arnaud
authors.initials: A
authors.lastname: Lanoue
authors.forename: Vincent
authors.initials: V
authors.lastname: Burlat
authors.forename: Gunnar J
authors.initials: GJ
authors.lastname: Henkes
authors.forename: Imke
authors.initials: I
authors.lastname: Koch
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schurr
authors.forename: Ursula S R
authors.initials: US
authors.lastname: Röse
mesh_terms: D000222:Adaptation, Physiological; D000935:Antifungal Agents / Q000378:metabolism*; D002245:Carbon Dioxide / Q000502:physiology; D002473:Cell Wall / Q000502:physiology; D002853:Chromatography, Liquid; D056229:Fungal Structures; D005670:Fusarium / Q000472:pathogenicity*; D001467:Hordeum / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D007554:Isotopes; D010636:Phenols / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D053147:Plant Exudates / Q000096:biosynthesis* / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D007554:Isotopes; D010636:Phenols; D053147:Plant Exudates; D002245:Carbon Dioxide