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Planta

, Volume 216, Issue 2, pp 334–344 | Cite as

Loss of the AKT2/3 potassium channel affects sugar loading into the phloem of Arabidopsis

  • Rosalia Deeken
  • Dietmar Geiger
  • Jörg Fromm
  • Olga Koroleva
  • Peter Ache
  • Rosemarie Langenfeld-Heyser
  • Norbert Sauer
  • Sean T. May
  • Rainer Hedrich
Original Article

Abstract.

Members of the AKT2/3 family have been identified as photosynthate-induced phloem K+ channels. Here we describe the isolation and characterisation of an AKT2/3 loss-of-function mutant (akt2/3-1) from Arabidopsis thaliana (L.) Heynh. Microautoradiography following 14CO2 incubation in the light revealed that a major fraction of 14CO2-derived photosynthates leaking out of sieve tubes appears not to be effectively reloaded (retrieval) into the phloem of the mutant. Using the aphid stylectomy technique we showed that the phloem sap of the mutant, lacking the phloem channels of the AKT2/3 type, contained only half the sucrose content of the wild type. Furthermore, the akt2/3-1 mutant exhibited a reduced K+ dependence of the phloem potential. Xenopus oocytes expressing the phloem sucrose/proton symporter depolarise upon sucrose application. When, however, the phloem channel was co-expressed – mimicking the situation in the sieve tube/companion cell complex – depolarisation was prevented. From our studies we thus conclude that AKT2/3 regulates the sucrose/H+ symporters via the phloem potential.

Arabidopsis Development (akt2/3-1 mutant) Phloem Potassium channel Sugar loading 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Rosalia Deeken
    • 1
  • Dietmar Geiger
    • 1
  • Jörg Fromm
    • 2
  • Olga Koroleva
    • 3
  • Peter Ache
    • 1
  • Rosemarie Langenfeld-Heyser
    • 4
  • Norbert Sauer
    • 5
  • Sean T. May
    • 6
  • Rainer Hedrich
    • 1
  1. 1.Julius-von-Sachs-Institute for Biosciences, Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany
  2. 2.Fachgebiet Angewandte Holzbiologie, Wissenschaftszentrum Weihenstephan der TU München, Winzerer Str. 4, 80797 München, Germany
  3. 3.School of Biological Sciences, University of Wales, Bangor, LL57 2UW, UK
  4. 4.Forstbotanisches Institut/Baumphysiologie, Büsgenweg 2, 37077 Göttingen, Germany
  5. 5.Lehrstuhl für Botanik II, Universität Erlangen, Staudstr. 5, 91058 Erlangen, Germany
  6. 6.Plant Science Division, School of Biosciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK

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