1. Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
2. Research Center for Cooperative Projects, Hokkaido University, Sapporo 060-8638, Japan
3. Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, Minnesota 55108
4. Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan
5. School of Life Science, Graduate University for Advanced Studies, Okazaki 444-8585, Japan