title: Knock-out of Arabidopsis metal transporter gene IRT1 results in iron deficiency accompanied by cell differentiation defects.
abstract: IRT1 and IRT2 are members of the Arabidopsis ZIP metal transporter family that are specifically induced by iron deprivation in roots and act as heterologous suppressors of yeast mutations inhibiting iron and zinc uptake. Although IRT1 and IRT2 are thought to perform redundant functions as root-specific metal transporters, insertional inactivation of the IRT1 gene alone results in typical symptoms of iron deficiency causing severe leaf chlorosis and lethality in soil. The irt1 mutation is characterized by specific developmental defects, including a drastic reduction of chloroplast thylakoid stacking into grana and lack of palisade parenchyma differentiation in leaves, reduced number of vascular bundles in stems, and irregular patterns of enlarged endodermal and cortex cells in roots. Pulse labeling with 59Fe through the root system shows that the irt1 mutation reduces iron accumulation in the shoots. Short-term labeling with 65Zn reveals no alteration in spatial distribution of zinc, but indicates a lower level of zinc accumulation. In comparison to wild-type, the irt1 mutant responds to iron and zinc deprivation by altered expression of certain zinc and iron transporter genes, which results in the activation of ZIP1 in shoots, reduction of ZIP2 transcript levels in roots, and enhanced expression of IRT2 in roots. These data support the conclusion that IRT1 is an essential metal transporter required for proper development and regulation of iron and zinc homeostasis in Arabidopsis.
authors.affiliation: ICAT, Faculdade de Ciências da Universidade de Lisboa, Portugal.
authors.forename: Rossana
authors.initials: R
authors.lastname: Henriques
authors.forename: Ján
authors.initials: J
authors.lastname: Jásik
authors.forename: Markus
authors.initials: M
authors.lastname: Klein
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Urs
authors.initials: U
authors.lastname: Feller
authors.forename: Jeff
authors.initials: J
authors.lastname: Schell
authors.forename: Maria S
authors.initials: MS
authors.lastname: Pais
authors.forename: Csaba
authors.initials: C
authors.lastname: Koncz
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D007501:Iron / Q000378:metabolism; D000090463:Iron Deficiencies; D016254:Mutagenesis, Insertional; D009154:Mutation; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015032:Zinc / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D004269:DNA, Bacterial; C099651:IRT1 protein, Arabidopsis; D018749:RNA, Plant; C036483:T-DNA; D007501:Iron; D015032:Zinc