1. Peking-Yale Joint Center of Plant Molecular Genetics and Agrobiotechnology, College of Life Sciences, Peking University, Beijing 100871, China
2. National Institute of Biological Sciences, Zhongguancun Life Science Park, Beijing 102206, China
3. Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104
4. Department of Biology and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802