1. M. Mena, B. A. Ambrose, M. F. Yanofsky, R. J. Schmidt, Department of Biology and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
2. R. B. Meeley and S. P. Briggs, Pioneer Hi-Bred International, Box 7300, Johnston, IA 50131, USA.