1. Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China;
2. Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520;
3. Department of Plant Pathology, Washington State University, Pullman, Washington 99164;