title: Transposon-mediated alteration of TaMATE1B expression in wheat confers constitutive citrate efflux from root apices.
abstract: The TaMATE1B gene (for multidrug and toxic compound extrusion) from wheat (Triticum aestivum) was isolated and shown to encode a citrate transporter that is located on the plasma membrane. TaMATE1B expression in roots was induced by iron deficiency but not by phosphorus deficiency or aluminum treatment. The coding region of TaMATE1B was identical in a genotype showing citrate efflux from root apices (cv Carazinho) to one that lacked citrate efflux (cv Egret). However, sequence upstream of the coding region differed between these two genotypes in two ways. The first difference was a single-nucleotide polymorphism located approximately 2 kb upstream from the start codon in cv Egret. The second difference was an 11.1-kb transposon-like element located 25 bp upstream of the start codon in cv Carazinho that was absent from cv Egret. The influence of these polymorphisms on TaMATE1B expression was investigated using fusions to green fluorescent protein expressed in transgenic lines of rice (Oryza sativa). Fluorescence measurements in roots of rice indicated that 1.5- and 2.3-kb regions upstream of TaMATE1B in cv Carazinho (which incorporated 3' regions of the transposon-like element) generated 20-fold greater expression in the apical 1 mm of root compared with the native promoter in cv Egret. By contrast, fluorescence in more mature tissues was similar in both cultivars. The presence of the single-nucleotide polymorphism alone consistently generated 2-fold greater fluorescence than the cv Egret promoter. We conclude that the transposon-like element in cv Carazinho extends TaMATE1B expression to the root apex, where it confers citrate efflux and enhanced aluminum tolerance.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Plant Industry, Canberra, Australian Capital Territory 2601, Australia.
authors.forename: Andriy
authors.initials: A
authors.lastname: Tovkach
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ryan
authors.forename: Alan E
authors.initials: AE
authors.lastname: Richardson
authors.forename: David C
authors.initials: DC
authors.lastname: Lewis
authors.forename: Tina M
authors.initials: TM
authors.lastname: Rathjen
authors.forename: Sunita
authors.initials: S
authors.lastname: Ramesh
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Tyerman
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Delhaize
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000494:pharmacology; D001483:Base Sequence; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism*; D004251:DNA Transposable Elements / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D020641:Polymorphism, Single Nucleotide; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014908:Triticum / Q000145:classification / Q000235:genetics* / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D010940:Plant Proteins; D049452:Green Fluorescent Proteins; D019343:Citric Acid; D000535:Aluminum