1. Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (M.T., J.W., K.S.M.); Department of Metabolic Biology, John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom (T.L.W.); and Institut des Sciences du Végétale, Unité Propre de Recherche 2355, CNRS, 91198 Gif sur Yvette, France (P.R.)