1. Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan, Central Research Laboratory, Ishihara Sangyo Kaisha Ltd., Kusatsu, Shiga 525-0025, Japan, and Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan