1. W. J. Lucas, S. Bouché-Pillon, L. Nguyen, L. Baker, B. Ding, Section of Plant Biology, Division of Biological Sciences, University of California, Davis, CA 95616, USA.
2. D. P. Jackson and S. Hake, U.S. Department of Agriculture-University of California Berkeley Plant Gene Expression Center, Albany, CA 94710, USA.