1. State Key Laboratory for Biocontrol, Guangzhou Key Laboratory of Pharmaceutical Functional Genes, Department of Biochemistry, College of Life Sciences, Sun Yat-sen (Zhongshan) University, Guangzhou, People's Republic of China.
2. These authors contributed equally to this work.
3. Present address: Department of Science of Prescription, College of Chinese Traditional Medicine, Guangzhou University of Traditional Chinese Medicine, Guangzhou, People's Republic of China.