title: Identification of the transporter responsible for sucrose accumulation in sugar beet taproots.
abstract: Sugar beet provides around one third of the sugar consumed worldwide and serves as a significant source of bioenergy in the form of ethanol. Sucrose accounts for up to 18% of plant fresh weight in sugar beet. Most of the sucrose is concentrated in the taproot, where it accumulates in the vacuoles. Despite 30 years of intensive research, the transporter that facilitates taproot sucrose accumulation has escaped identification. Here, we combine proteomic analyses of the taproot vacuolar membrane, the tonoplast, with electrophysiological analyses to show that the transporter BvTST2.1 is responsible for vacuolar sucrose uptake in sugar beet taproots. We show that BvTST2.1 is a sucrose-specific transporter, and present evidence to suggest that it operates as a proton antiporter, coupling the import of sucrose into the vacuole to the export of protons. BvTST2.1 exhibits a high amino acid sequence similarity to members of the tonoplast monosaccharide transporter family in Arabidopsis, prompting us to rename this group of proteins 'tonoplast sugar transporters'. The identification of BvTST2.1 could help to increase sugar yields from sugar beet and other sugar-storing plants in future breeding programs.
authors.affiliation: Pflanzenphysiologie, University Kaiserslautern, Erwin Schrödinger Straße, D-67653 Kaiserslautern, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Jung
authors.affiliation: Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Zülpicher Straße 47b, D-50674, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Ludewig
authors.affiliation: Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schulz
authors.affiliation: Pflanzenphysiologie, University Kaiserslautern, Erwin Schrödinger Straße, D-67653 Kaiserslautern, Germany.
authors.forename: Garvin
authors.initials: G
authors.lastname: Meißner
authors.affiliation: Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Zülpicher Straße 47b, D-50674, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Wöstefeld
authors.affiliation: Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Zülpicher Straße 47b, D-50674, Germany.
authors.forename: Ulf-Ingo
authors.initials: UI
authors.lastname: Flügge
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nuremberg, Staudtstraße 5, D-91058 Erlangen, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pommerrenig
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nuremberg, Staudtstraße 5, D-91058 Erlangen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Wirsching
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nuremberg, Staudtstraße 5, D-91058 Erlangen, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Sauer
authors.affiliation: KWS Saat AG, Grimsehlstr.31, D37555 Einbeck, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Koch
authors.affiliation: Molecular Biotechnology and Systems Biology, University Kaiserslautern, Paul-Ehrlich-Straße, D-67653 Kaiserslautern Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Sommer
authors.affiliation: Molecular Biotechnology and Systems Biology, University Kaiserslautern, Paul-Ehrlich-Straße, D-67653 Kaiserslautern Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Mühlhaus
authors.affiliation: Molecular Biotechnology and Systems Biology, University Kaiserslautern, Paul-Ehrlich-Straße, D-67653 Kaiserslautern Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schroda
authors.affiliation: Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany.
authors.forename: Tracey Ann
authors.initials: TA
authors.lastname: Cuin
authors.affiliation: Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Graus
authors.affiliation: Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Marten
authors.affiliation: Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.affiliation: Pflanzenphysiologie, University Kaiserslautern, Erwin Schrödinger Straße, D-67653 Kaiserslautern, Germany.
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus