1. Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, B-9052 Ghent, Belgium
2. U.S. Dairy Forage Research Center, U.S. Department of Agriculture-Agricultural Research Service, Madison, Wisconsin 53706
3. Centre de Recherche des Macromolécules Végétales, Centre National de la Recherche Scientifique, F-38041 Grenoble Cedex 09, France
4. Vakgroep Biochemie, Fysiologie en Microbiologie, Universiteit Gent, B-9000 Gent, Belgium