1. Hybridoma Facility, University of California, Berkeley College of Natural Resources, 1050 San Pablo Avenue, Albany, CA 94706
2. Department of Molecular Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037
3. Department of Plant Biology, University of California, Berkeley, CA 94720
4. Current address: Department of Transplantation Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261