title: Functional characterisation and cell specificity of BvSUT1, the transporter that loads sucrose into the phloem of sugar beet (Beta vulgaris L.) source leaves.
abstract: Sugar beet (Beta vulgaris L.) is one of the most important sugar-producing plants worldwide and provides about one third of the sugar consumed by humans. Here we report on molecular characterisation of the BvSUT1 gene and on the functional characterisation of the encoded transporter. In contrast to the recently identified tonoplast-localised sucrose transporter BvTST2.1 from sugar beet taproots, which evolved within the monosaccharide transporter (MST) superfamily, BvSUT1 represents a classical sucrose transporter and is a typical member of the disaccharide transporter (DST) superfamily. Transgenic Arabidopsis plants expressing the β-GLUCURONIDASE (GUS) reporter gene under control of the BvSUT1-promoter showed GUS histochemical staining of their phloem; an anti-BvSUT1-antiserum identified the BvSUT1 transporter specifically in phloem companion cells. After expression of BvSUT1 cDNA in bakers' yeasts (Saccharomyces cerevisiae) uptake characteristics of the BvSUT1 protein were studied. Moreover, the sugar beet transporter was characterised as a proton-coupled sucrose symporter in Xenopus laevis oocytes. Our findings indicate that BvSUT1 is the sucrose transporter that is responsible for loading of sucrose into the phloem of sugar beet source leaves delivering sucrose to the storage tissue in sugar beet taproot sinks.
authors.affiliation: Molecular Plant Physiology (MPP), FAU Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Nieberl
authors.affiliation: Molecular Plant Physiology (MPP), FAU Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ehrl
authors.affiliation: Molecular Plant Physiology (MPP), FAU Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Pommerrenig
authors.affiliation: Biophysics and Molecular Plant Physiology, University of Würzburg, Würzburg, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Graus
authors.affiliation: Biophysics and Molecular Plant Physiology, University of Würzburg, Würzburg, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Marten
authors.affiliation: Plant Physiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Jung
authors.affiliation: Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Ludewig
authors.affiliation: KWS Saat AG, Einbeck, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Koch
authors.affiliation: SÜDZUCKER AG, CRDS, Obrigheim/Pfalz, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Harms
authors.affiliation: Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany.
authors.forename: U-I
authors.initials: UI
authors.lastname: Flügge
authors.affiliation: Plant Physiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: H E
authors.initials: HE
authors.lastname: Neuhaus
authors.affiliation: Biophysics and Molecular Plant Physiology, University of Würzburg, Würzburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Hedrich
authors.affiliation: Molecular Plant Physiology (MPP), FAU Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Sauer
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D027461:Beta vulgaris / Q000235:genetics / Q000378:metabolism*; D005260:Female; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D052585:Phloem / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013395:Sucrose / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; C078729:sucrose transport protein, plant; D013395:Sucrose; D005966:Glucuronidase
keywords: BvSUT1; companion cells; heterologous expression; phloem loading; sucrose transport; sugar beet