Department of Plant Systems Biology, VIB, Department of Molecular Genetics, Ghent University, Technologiepark 927, B-9052 Gent, Belgium. jehol@psb.vib-ugent.be|Department of Plant Systems Biology, VIB, Department of Molecular Genetics, Ghent University, Technologiepark 927, B-9052 Gent, Belgium. jehol@psb.vib-ugent.be|Department of Plant Systems Biology, VIB, Department of Molecular Genetics, Ghent University, Technologiepark 927, B-9052 Gent, Belgium. jehol@psb.vib-ugent.be|Department of Plant Systems Biology, VIB, Department of Molecular Genetics, Ghent University, Technologiepark 927, B-9052 Gent, Belgium. jehol@psb.vib-ugent.be