Laboratory for Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Leuven, Belgium; 2Institut de Pharmacologie et ´ Biologie Structurale, Unite Mixte de Recherche Centre National de la Recherche Scientifique 5089, Toulouse, France; 3Institute of Plant Biochemistry, Halle, Germany; 4Laboratory of Developmental Physiology and Molecular Biology, Katholieke Universiteit Leuven, Leuven, Belgium