1. Norwegian University of Life Sciences (NMBU), Faculty of Chemistry, Biotechnology, and Food Science, P.O. Box 5003, ÅsN-1432, Norway
2. Joint BioEnergy Institute, Emeryville, California94608, United States
3. Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
4. Institut für Genetik, Technische Universität Braunschweig, Spielmannstr. 7, Braunschweig38106, Germany