1. Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant HillBeijing 100093 China
2. University of Chinese Academy of SciencesBeijing 100049 China
3. Department of Plant Biology, College of Biological SciencesUniversity of CaliforniaDavis CA 95616 USA
4. Institute of Crop Sciences, Chinese Academy of Agricultural SciencesBeijing 100081 China