1. Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York 11794–5215 (G.-W.T., B.P., C.D.K., J.L., V.C.); Watson School of Biological Sciences (C.D.K.) and Cold Spring Harbor Laboratory (A.M., D.J.), Cold Spring Harbor, New York 11724; Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 9