Article

Identification of the transporter responsible for sucrose accumulation in sugar beet taproots

  • Nature Plants volume 1, Article number: 14001 (2015)
  • doi:10.1038/nplants.2014.1
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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.

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Acknowledgements

Work in the labs of H.E.N., R.H., U-I.F. and N.S. was financially supported by BMBF (Betamorphosis). Work in the lab of R.H. and H.E.N. was additionally supported by the Deutsche Forschungsgemeinschaft (FOR1061) and the Federal State of Rhineland Palatinate (BioComp). We thank Maike Müller for technical assistance. We are grateful to Karsten Harms for supporting project planning and comments on the manuscript.

Author information

Author notes

    • Benjamin Jung
    • , Frank Ludewig
    •  & Alexander Schulz

    These authors contributed equally to this work

Affiliations

  1. Pflanzenphysiologie, University Kaiserslautern, Erwin Schrödinger Straße, D-67653 Kaiserslautern, Germany

    • Benjamin Jung
    • , Garvin Meißner
    •  & H. Ekkehard Neuhaus
  2. Biocenter Cologne, Botanical Institute II and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Zülpicher Straße 47b, D-50674, Germany

    • Frank Ludewig
    • , Nicole Wöstefeld
    •  & Ulf-Ingo Flügge
  3. Biophysics and Molecular Plant Physiology, University Würzburg, Julius von Sachs Platz 2, D-97082 Würzburg, Germany

    • Alexander Schulz
    • , Tracey Ann Cuin
    • , Dorothea Graus
    • , Irene Marten
    •  & Rainer Hedrich
  4. Molecular Plant Physiology, University Erlangen-Nuremberg, Staudtstraße 5, D-91058 Erlangen, Germany

    • Benjamin Pommerrenig
    • , Petra Wirsching
    •  & Norbert Sauer
  5. KWS Saat AG, Grimsehlstr.31, D37555 Einbeck, Germany

    • Wolfgang Koch
  6. Molecular Biotechnology and Systems Biology, University Kaiserslautern, Paul-Ehrlich-Straße, D-67653 Kaiserslautern Germany

    • Frederik Sommer
    • , Timo Mühlhaus
    •  & Michael Schroda

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Contributions

B.J. conceived and conducted vacuole preparation; conceived the cloning of GFP fusion constructs and localization studies; and conducted phylogenetic analyses. B.J. and G.M. conceived, performed and analysed the expression studies. B.J., G.M. and N.W. performed sugar determination, growth experiments and generation of transgenic plants. A.S., I.M., D.G. and T.A.C. conducted electrophysiological measurements. B.P. and P.W. studied subcellular localizations. F.S., T.M. and M.S. conceived and conducted proteomic analyses. W.K. provided access to the B. vulgaris nucleotide sequences. F.L., U-I.F., N.S., I.M., R.H. and H.E.N. designed and conceived the study. H.E.N. wrote the manuscript. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Rainer Hedrich or H. Ekkehard Neuhaus.

Supplementary information