title: Iron distribution through the developmental stages of Medicago truncatula nodules.
abstract: Paramount to symbiotic nitrogen fixation (SNF) is the synthesis of a number of metalloenzymes that use iron as a critical component of their catalytical core. Since this process is carried out by endosymbiotic rhizobia living in legume root nodules, the mechanisms involved in iron delivery to the rhizobia-containing cells are critical for SNF. In order to gain insight into iron transport to the nodule, we have used synchrotron-based X-ray fluorescence to determine the spatio-temporal distribution of this metal in nodules of the legume Medicago truncatula with hitherto unattained sensitivity and resolution. The data support a model in which iron is released from the vasculature into the apoplast of the infection/differentiation zone of the nodule (zone II). The infected cell subsequently takes up this apoplastic iron and delivers it to the symbiosome and the secretory system to synthesize ferroproteins. Upon senescence, iron is relocated to the vasculature to be reused by the shoot. These observations highlight the important role of yet to be discovered metal transporters in iron compartmentalization in the nodule and in the recovery of an essential and scarce nutrient for flowering and seed production.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Campus de Montegancedo, Crta. M40 km 37, 28223 Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Benjamín
authors.initials: B
authors.lastname: Rodríguez-Haas
authors.forename: Lydia
authors.initials: L
authors.lastname: Finney
authors.forename: Stefan
authors.initials: S
authors.lastname: Vogt
authors.forename: Pablo
authors.initials: P
authors.lastname: González-Melendi
authors.forename: Juan
authors.initials: J
authors.lastname: Imperial
authors.forename: Manuel
authors.initials: M
authors.lastname: González-Guerrero
mesh_terms: D001692:Biological Transport; D054884:Host-Pathogen Interactions; D007501:Iron / Q000378:metabolism*; D046913:Medicago truncatula / Q000254:growth & development / Q000378:metabolism*; D008667:Metalloproteins / Q000096:biosynthesis; D008954:Models, Biological; D009586:Nitrogen Fixation; D053204:Root Nodules, Plant / Q000378:metabolism* / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000378:metabolism* / Q000502:physiology; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013559:Symbiosis; D017356:Synchrotrons
chemical_list: D008667:Metalloproteins; D007501:Iron