1. Department of Plant Biology, Cornell University, Ithaca, New York 14853
2. Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-10691 Stockholm, Sweden
3. Stockholm Bioinformatics Center, Stockholm University, S-10691 Stockholm, Sweden
4. Department of Molecular Biology, Odense University, DK-5230 Odense M, Denmark