1 Cell Biology and Plant Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany. thomas.dresselhaus@ur.de.
2 Laboratory of Biochemistry, Wageningen University, Stippeneng 4, 6708WE, Wageningen, The Netherlands. dolf.weijers@wur.nl.