title: Enhancing the aluminium tolerance of barley by expressing the citrate transporter genes SbMATE and FRD3.
abstract: Malate and citrate efflux from root apices is a mechanism of Al(3+) tolerance in many plant species. Citrate efflux is facilitated by members of the MATE (multidrug and toxic compound exudation) family localized to the plasma membrane of root cells. Barley (Hordeum vulgare) is among the most Al(3+)-sensitive cereal species but the small genotypic variation in tolerance that is present is correlated with citrate efflux via a MATE transporter named HvAACT1. This study used a biotechnological approach to increase the Al(3+) tolerance of barley by transforming it with two MATE genes that encode citrate transporters: SbMATE is the major Al(3+)-tolerance gene from sorghum whereas FRD3 is involved with Fe nutrition in Arabidopsis. Independent transgenic and null T3 lines were generated for both transgenes. Lines expressing SbMATE showed Al(3+)-activated citrate efflux from root apices and greater tolerance to Al(3+) toxicity than nulls in hydroponic and short-term soil trials. Transgenic lines expressing FRD3 exhibited similar phenotypes except citrate release from roots occurred constitutively. The Al(3+) tolerance of these lines was compared with previously generated transgenic barley lines overexpressing the endogenous HvAACT1 gene and the TaALMT1 gene from wheat. Barley lines expressing TaALMT1 showed significantly greater Al(3+) tolerance than all lines expressing MATE genes. This study highlights the relative efficacy of different organic anion transport proteins for increasing the Al(3+) tolerance of an important crop species.
authors.affiliation: Tasmanian Institute of Agriculture, University of Tasmania, PO Box 46, Kings Meadows, TAS 7249, Australia CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors.forename: Gaofeng
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Embrapa Wheat, Rodovia BR 285 km 294, CEP 99001-970, Passo Fundo, RS, Brazil.
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Pereira
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Delhaize
authors.affiliation: Tasmanian Institute of Agriculture, University of Tasmania, PO Box 46, Kings Meadows, TAS 7249, Australia.
authors.forename: Meixue
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Embrapa Maize and Sorghum, Rod. MG 424, Km 65, 35701-970, Sete Lagoas, Minas Gerais, Brazil.
authors.forename: Jurandir V
authors.initials: JV
authors.lastname: Magalhaes
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia Peter.Ryan@csiro.au.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ryan
mesh_terms: D000535:Aluminum / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D001467:Hordeum / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D045868:Sorghum / Q000235:genetics*; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C469252:FRD3 protein, Arabidopsis; D026901:Membrane Transport Proteins; D010940:Plant Proteins; C020723:citrate-binding transport protein; D000535:Aluminum
keywords: Acid soil; Hordeum vulgare; MATE transporters; cereal; citrate; resistance; root exudates; transgenic.