1. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan; Centre de Recherches sur les Macromolécules Végétales (Affiliated with Joseph Fourier University of Grenoble), C.N.R.S. B.P. 53, 38401, Grenoble Cedex 9, France; and Wood Research Institute, Kyoto University, Kyoto 611-0011, Japan