1. Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA, Wageningen, The Netherlands, Plant Research International, Wageningen University and Research Centre, POB 16, 6700 AA, Wageningen, The Netherlands, Laboratory of Plant Physiology, Wageningen University, POB 658, 6700 AR, Wageningen, The Netherlands, Centre for Biosystems Genomics, POB 98, 6700 AB, Wageningen, The Netherlands, and Netherlands Metabolomics Centre, Einsteinweg 55, 2333 CC, Leiden, The Netherlands