1. Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109–1048 (G.Y., T.T.H.N., I.S., N.B., Y.I., E.P.); Howard Hughes Medical Institute, Salk Institute for Biological Studies, Jack H. Skirball Center for Chemical Biology and Proteomics, La Jolla, California 92037 (Y.G., M.E.A., J.P.N.); Robert H. Smith Institute of Plant Sciences and Genetics