1. Department of Vegetative Physiology, University of Cologne, Robert Koch‐Straße 39, D‐50931 Cologne, Germany
2. Glaxo‐IMCB Group, Institute of Molecular and Cell Biology, National University of Singapore, Kent Ridge, Singapore 0511, USA
3. Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC 27858‐4354, USA
4. Department of Physiology and Biophysics, University of Illinois, Chicago, IL 60612, USA