Barley mildew and its elicitor chitosan promote closed stomata by stimulating guard-cell S-type anion channels

Authors

  • Sandra Koers,

    1. Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany
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  • Aysin Guzel-Deger,

    1. Department of Biology, Faculty of Science and Letters, University of Mersin, 33343 Mersin, Turkey
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  • Irene Marten,

    1. Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany
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  • M. Rob G. Roelfsema

    Corresponding author
    1. Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany
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(fax +49 931 3186158; e-mail roelfsema@botanik.uni-wuerzburg.de).

Summary

Stomatal closure is known to be associated with early defence responses of plant cells triggered by microbe-associated molecular patterns (MAMPs). However, the molecular mechanisms underlying these guard-cell responses have not yet been elucidated. We therefore studied pathogen-induced changes in ion channel activity in Hordeum vulgare guard cells. Barley mildew (Blumeria graminis) hyphae growing on leaves inhibited light-induced stomatal opening, starting at 9 h after inoculation, when appressoria had developed. Alternatively, stomatal closure was induced by nano-infusion of chitosan via open stomata into the sub-stomatal cavity. Experiments using intracellular double-barreled micro-electrodes revealed that mildew stimulated S-type (slow) anion channels in guard cells. These channels enable the efflux of anions from guard cells and also promote K+ extrusion by altering the plasma membrane potential. Stimulation of S-type anion channels was also provoked by nano-infusion of chitosan. These data suggest that MAMPs of mildew hyphae penetrating the cuticle provoke activation of S-type anion channels in guard cells. In response, guard cells extrude K+ salts, resulting in stomatal closure. Plasma membrane anion channels probably represent general targets of MAMP signaling in plants, as these elicitors depolarize the plasma membrane of various cell types.

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