title: Involvement of nitrogen functional groups in high-affinity copper binding in tomato and wheat root apoplasts: spectroscopic and thermodynamic evidence.
abstract: Carboxylic groups located in plant cell walls (CW) are generally considered to be the main copper binding sites in plant roots, despite the presence of other functional groups. The aim of this study was to investigate sites responsible for copper binding in root apoplasts, i.e. CW and outer surface of the plasma membrane (PM) continuum. Binding sites in root apoplasts were investigated by comparing isolated CW of a monocotyledon (Triticum aestivum L.) and dicotyledon (Solanum lycopersicum L.) crop with their respective whole roots. Copper speciation was examined by X-ray absorption (XAS) and (13)C-nuclear magnetic resonance spectroscopies while the affinity of ligands involved in copper binding was investigated by modeling copper sorption isotherms. Homogeneous speciation and binding of copper was found in wheat and tomato root apoplasts. Only Cu-N and Cu-O bonds were detected in wheat and tomato root apoplasts. Nitrogen/oxygen ligands were identified in slightly higher proportions (40-70%) than single oxygen ligands. Furthermore, low- and high-affinity binding sites contributed in an almost equivalent proportion to copper binding in root apoplasts. The high-affinity N functional groups embedded in root apoplasts participated in copper binding in the same magnitude than the low-affinity carboxylic groups.
authors.affiliation: CIRAD, UPR Recyclage et risque, F-34398 Montpellier, France. doelsch@cirad.fr and ADEME, 20 avenue du Grésillé, BP-90406, Angers cedex 01, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Guigues
authors.affiliation: CIRAD, UPR Recyclage et risque, F-97408 Saint-Denis, Réunion, France.
authors.forename: Matthieu N
authors.initials: MN
authors.lastname: Bravin
authors.affiliation: Université de Toulon, PROTEE, EA 3819, 83957 La Garde, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Garnier
authors.affiliation: CNRS, Aix-Marseille Université, IRD, CEREGE UM34, 13545 Aix-en-Provence, France.
authors.forename: Armand
authors.initials: A
authors.lastname: Masion
authors.affiliation: CIRAD, UPR Recyclage et risque, F-34398 Montpellier, France. doelsch@cirad.fr.
authors.forename: Claire
authors.initials: C
authors.lastname: Chevassus-Rosset
authors.affiliation: CIRAD, UPR Recyclage et risque, F-34398 Montpellier, France. doelsch@cirad.fr.
authors.forename: Patrick
authors.initials: P
authors.lastname: Cazevieille
authors.affiliation: CIRAD, UPR Recyclage et risque, F-34398 Montpellier, France. doelsch@cirad.fr.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Doelsch
mesh_terms: D066241:Carbon-13 Magnetic Resonance Spectroscopy; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D008024:Ligands; D018551:Solanum lycopersicum / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D013816:Thermodynamics; D014908:Triticum / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008024:Ligands; D003300:Copper; D009584:Nitrogen