title: Manganese efficiency in barley: identification and characterization of the metal ion transporter HvIRT1.
abstract: Manganese (Mn) deficiency is an important plant nutritional disorder in many parts of the world. Barley (Hordeum vulgare) genotypes differ considerably in their ability to grow in soils with low Mn(2+) availability. Differential genotypic Mn efficiency can be attributed to differences in Mn(2+) uptake kinetics in the low nanomolar concentration range. However, the molecular basis for these differences has not yet been clarified. We present here the identification and characterization of the first barley gene encoding a plasma membrane-localized metal transport protein able to transport Mn(2+). The gene is designated HvIRT1 (for IRON-REGULATED TRANSPORTER1) because it belongs to the ZIP gene family and has a high similarity to rice (Oryza sativa) OsIRT1. A novel yeast uptake assay based on inductively coupled plasma-mass spectrometry analysis of 31 different metal and metalloid ions showed that the HvIRT1 protein, in addition to Mn(2+), also transported Fe(2+)/Fe(3+), Zn(2+), and Cd(2+). Both Mn and iron deficiency induced an up-regulation of HvIRT1 in two barley genotypes differing in Mn efficiency, but the expression levels in all cases were highest (up to 40%) in the Mn-efficient genotype. The higher expression of HvIRT1 correlated with an increased Mn(2+) uptake rate. We conclude that HvIRT1 is an important component controlling Mn(2+) uptake in barley roots and contributes to genotypic differences in Mn(2+) uptake kinetics.
authors.affiliation: Plant and Soil Science Laboratory, Department of Agriculture and Ecology , Faculty of Life Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Copenhagen, Denmark. pp@life.ku.dk
authors.forename: Pai
authors.initials: P
authors.lastname: Pedas
authors.forename: Cecilie K
authors.initials: CK
authors.lastname: Ytting
authors.forename: Anja T
authors.initials: AT
authors.lastname: Fuglsang
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Jahn
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.forename: Søren
authors.initials: S
authors.lastname: Husted
mesh_terms: D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D005816:Genetic Complementation Test; D005838:Genotype; D001467:Hordeum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000737:chemistry; D018517:Plant Roots / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D014131:Trace Elements / Q000378:metabolism
chemical_list: D027682:Cation Transport Proteins; D019216:Metals, Heavy; D014131:Trace Elements; D008345:Manganese