1. Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan
2. Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, B-9, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
3. Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan