Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-University München, Germany, Max-Planck-Institute for Plant Breeding Research, Cologne, Germany Department of Biology, Albertus-Magnus University, Cologne, Germany, Institute for Medical Informatics and Biometry, Faculty of Medicine Carl Gustav Carus, TU Dresden, Germany, Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany and Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland.