Planta

, Volume 207, Issue 4, pp 612–619

Analysis of phloem protein patterns from different organs of Cucurbita maxima Duch. by matrix-assisted laser desorption/ionization time of flight mass spectroscopy combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis

  • Julia Kehr
  • Sophie Haebel
  • Sabine Blechschmidt-Schneider
  • Lothar Willmitzer
  • Martin Steup
  • Joachim Fisahn
Article

Abstract.

Sieve tubes mediate the long-distance transport of nutrients and signals between source and sink organs of plants. To detect mobile phloem proteins that are differentially distributed in source and sink organs of Cucurbita maxima, we used both one-dimensional gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Both techniques revealed that phloem protein patterns depend on the sampling site: whilst several proteins were consistently observed in all phloem samples studied others appeared to occur in a organ-specific manner. For a characterization and identification of distinct phloem polypeptides, two approaches were chosen. First, protein bands resolved by SDS-PAGE were eluted from the polyacrylamide gel and the masses of the proteins were then determined by MALDI-TOF MS. Second, proteins resolved by SDS-PAGE were subjected to proteolytic degradation and the resulting peptides were analyzed by MALDI-TOF MS; the masses of the proteolytic peptides were used for a database search. By the latter approach, three mobile phloem compounds were identified as the phloem-specific protein PP2 (D.E. Bostwick et al., 1992, The Plant Cell 4, 1539–1548) a chymotrypsin and an aspartic proteinase inhibitor. None of the other polypeptides studied corresponded to any of the protein sequences present in the database. Furthermore, MALDI-TOF MS analyses indicated that some of the mobile phloem proteins occur in a covalently modified form and that the extent of the modification depends upon the plant organ.

Key words:Cucurbita (phloem proteins) Phloem protein Protein modification 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Julia Kehr
    • 1
  • Sophie Haebel
    • 2
  • Sabine Blechschmidt-Schneider
    • 3
  • Lothar Willmitzer
    • 1
  • Martin Steup
    • 4
  • Joachim Fisahn
    • 1
  1. 1.Max-Planck-Institut für Molekulare Pflanzenphysiologie, Karl-Liebknecht-Str. 25, D-14476 Golm, GermanyDE
  2. 2.Zentrum für Biopolymere, Universität Potsdam, Komplex I, Am Neuen Palais 10, D-14469 Potsdam, GermanyDE
  3. 3.Institut für Forstbotanik, Universität Göttingen, Büsgenweg 2, D-37077 Göttingen, GermanyDE
  4. 4.Institut für Biochemie und Molekulare Physiologie, Universität Potsdam, Maulbeerallee 2, D-14469 Potsdam, GermanyDE

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