1. Laboratory of Molecular Cell Biology, Temasek Life Science Laboratory, National University of Singapore, 117604 Singapore
2. National Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China
3. National Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, People's Republic of China
4. Laboratory of Plant Molecular Biology, The Rockefeller University, New York, New York 10021