1. Department of Plant Microbe Interactions, Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, D-50829 Köln, Germany.
2. Institute of Physiology II, Friedrich-Schiller-University of Jena, Teichgraben 8, D-07740 Jena, Germany.
3. Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland.