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Keywords:

  • elicitor;
  • endocytosis;
  • lipopolysaccharides;
  • LPS;
  • plant–microbe interaction;
  • signaltransduction

Summary

  • • 
    The specific recognition of phytopathogenic bacteria by plant cells is generally mediated by a number of signal molecules. The elicitor-active lipopolysaccharides (LPS) of the phytopathogenic bacterium Xanthomonas campestris pv. campestris (X.c.c) are recognized by its non-host plant Nicotiana tabacum (N.t.).
  • • 
    This LPS was purified and labelled with fluorescein isothiocyanate (FITC) for monitoring the fate of these signal molecules in intact plant cells of tobacco.
  • • 
    In this study we were able to show that the so-labelled LPS rapidly bound to the cell wall and was then internalized into the cells in a temperature- and energy-dependent way. This uptake of LPS could be outcompeted by the addition of an excess of unlabelled LPS. Furthermore, it was blocked by amantadine, an inhibitor of receptor-mediated endocytosis of mammalian cells. Immunolocalization experiments showed for the first time a significant co-localization of the LPS-elicitor with endosomal structures using an anti-Ara6 antibody.
  • • 
    These observations suggest specific endocytosis of LPSX.c.c. into tobacco cells. The possibility for a receptor-mediated endocytosis comparable to the mammalian system will be discussed.