1. Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan, and Novelty Materials Research Institute, Tsukaba R&D Center, Fuji Oil Co. Ltd., 4-3 Kinunodai, Yawara, Tsukuba-gun, Ibaraki 300-2497, Japan