title: Arabidopsis thaliana AtUTr7 encodes a golgi-localized UDP-glucose/UDP-galactose transporter that affects lateral root emergence.
abstract: Nucleotide sugar transporters (NSTs) are antiporters comprising a gene family that plays a fundamental role in the biosynthesis of complex cell wall polysaccharides and glycoproteins in plants. However, due to the limited number of related mutants that have observable phenotypes, the biological function(s) of most NSTs in cell wall biosynthesis and assembly have remained elusive. Here, we report the characterization of AtUTr7 from Arabidopsis (Arabidopsis thaliana (L.) Heynh.), which is homologous to multi-specific UDP-sugar transporters from Drosophila melanogaster, humans, and Caenorhabditis elegans. We show that AtUTr7 possesses the common structural characteristics conserved among NSTs. Using a green fluorescent protein (GFP) tagged version, we demonstrate that AtUTr7 is localized in the Golgi apparatus. We also show that AtUTr7 is widely expressed, especially in the roots and in specific floral organs. Additionally, the results of an in vitro nucleotide sugar transport assay carried out with a tobacco and a yeast expression system suggest that AtUTr7 is capable of transferring UDP-Gal and UDP-Glc, but not a range of other UDP- and GDP-sugars, into the Golgi lumen. Mutants lacking expression of AtUTr7 exhibited an early proliferation of lateral roots as well as distorted root hairs when cultivated at high sucrose concentrations. Furthermore, the distribution of homogalacturonan with a low degree of methyl esterification differed in lateral root tips of the mutant compared to wild-type plants, although additional analytical procedures revealed no further differences in the composition of the root cell walls. This evidence suggests that the transport of UDP-Gal and UDP-Glc into the Golgi under conditions of high root biomass production plays a role in lateral root and root hair development.
authors.affiliation: Department of Biology, University of Chile, Santiago, Chile.
authors.forename: Michael
authors.initials: M
authors.lastname: Handford
authors.forename: Cecilia
authors.initials: C
authors.lastname: Rodríguez-Furlán
authors.forename: Lorena
authors.initials: L
authors.lastname: Marchant
authors.forename: Marcelo
authors.initials: M
authors.lastname: Segura
authors.forename: Daniela
authors.initials: D
authors.lastname: Gómez
authors.forename: Elena
authors.initials: E
authors.lastname: Alvarez-Buylla
authors.forename: Guang-Yan
authors.initials: GY
authors.lastname: Xiong
authors.forename: Markus
authors.initials: M
authors.lastname: Pauly
authors.forename: Ariel
authors.initials: A
authors.lastname: Orellana
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006056:Golgi Apparatus / Q000378:metabolism*; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D018517:Plant Roots / Q000254:growth & development*; D021381:Protein Transport; D017421:Sequence Analysis; D013379:Substrate Specificity; D014532:Uridine Diphosphate Glucose / Q000378:metabolism*; D000099237:UDP-Galactose Translocators
chemical_list: D009004:Monosaccharide Transport Proteins; D014532:Uridine Diphosphate Glucose; D000099237:UDP-Galactose Translocators