1. Department of Plant and Soil Sciences; Institute for Agricultural Biosciences; Oklahoma State University; 3210 Sam Noble Parkway Ardmore OK 73401 USA
2. Biotechnology Research Institute; Chinese Academy of Agricultural Sciences; Beijing 100081 China
3. Plant Biology Division; The Samuel Roberts Noble Foundation; 2510 Sam Noble Parkway Ardmore OK 73401 USA
4. Institut des Sciences du Végétal; Centre National de la Recherche Scientifique; Saclay Plant Sciences; 91198 Gif sur Yvette Cedex France