1. Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
2. Commonwealth Scientific and Industrial Research Organization, Division of Health Sciences and Nutrition, 343 Royal Parade, Parkville, Victoria 3052, Australia
3. The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia
4. Centre de Recherches sur les Macromolécules Végétales, Centre National de la Recherche Scientifique (affiliated with Université Joseph Fourier), BP 53, 38041 Grenoble cedex 09, France