title: The expression of heterologous Fe (III) phytosiderophore transporter HvYS1 in rice increases Fe uptake, translocation and seed loading and excludes heavy metals by selective Fe transport.
abstract: Many metal transporters in plants are promiscuous, accommodating multiple divalent cations including some which are toxic to humans. Previous attempts to increase the iron (Fe) and zinc (Zn) content of rice endosperm by overexpressing different metal transporters have therefore led unintentionally to the accumulation of copper (Cu), manganese (Mn) and cadmium (Cd). Unlike other metal transporters, barley Yellow Stripe 1 (HvYS1) is specific for Fe. We investigated the mechanistic basis of this preference by constitutively expressing HvYS1 in rice under the control of the maize ubiquitin1 promoter and comparing the mobilization and loading of different metals. Plants expressing HvYS1 showed modest increases in Fe uptake, root-to-shoot translocation, seed accumulation and endosperm loading, but without any change in the uptake and root-to-shoot translocation of Zn, Mn or Cu, confirming the selective transport of Fe. The concentrations of Zn and Mn in the endosperm did not differ significantly between the wild-type and HvYS1 lines, but the transgenic endosperm contained significantly lower concentrations of Cu. Furthermore, the transgenic lines showed a significantly reduced Cd uptake, root-to-shoot translocation and accumulation in the seeds. The underlying mechanism of metal uptake and translocation reflects the down-regulation of promiscuous endogenous metal transporters revealing an internal feedback mechanism that limits seed loading with Fe. This promotes the preferential mobilization and loading of Fe, therefore displacing Cu and Cd in the seed.
authors.affiliation: Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center Lleida, Lleida, Spain.
authors.forename: Raviraj
authors.initials: R
authors.lastname: Banakar
authors.affiliation: Department of Plant Nutrition, Aula Dei Experimental Station, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain.
authors.forename: Ána
authors.initials: Á
authors.lastname: Alvarez Fernández
authors.affiliation: Department of Plant Nutrition, Aula Dei Experimental Station, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Abadía
authors.affiliation: Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center Lleida, Lleida, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Capell
authors.affiliation: Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida-Agrotecnio Center Lleida, Lleida, Spain.|ICREA, Catalan Institute for Research and Advanced Studies, Barcelona, Spain.
authors.forename: Paul
authors.initials: P
authors.lastname: Christou
mesh_terms: D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism; D001467:Hordeum / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism*; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D019216:Metals, Heavy; D010940:Plant Proteins; D002104:Cadmium; D008345:Manganese; D007501:Iron; D015032:Zinc
keywords: 2′ deoxymugenic acid; Rice; barley YS1 transporter; iron; metal transporters; toxic metals