1. State Key Laboratory of Agrobiotechnology, College of Biological Sciences China Agricultural University Beijing 100193 China
2. State Key Laboratory of Plant Physiology and Biochemistry, Engineering Research Center of Plant Growth Regulator, Ministry of Education, College of Agronomy and Biotechnology China Agricultural University Beijing 100193 China
3. State Key Laboratory of Plant Physiology and Biochemistry, National Maize Improvement Center, Department of Plant Genetics and Breeding China Agricultural University Beijing 100193 China