1. Universiteit Gent, K.L. Ledeganckstraat 35, B-9000, Gent, Belgium
2. Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, California 94720
3. Institut des Sciences du Végétal-CNRS, Service de Cytométrie, avenue de la Terrasse, 91198 Gif-sur-Yvette, France
4. Department of Genetics, University of Melbourne, Parkville 3052, Australia