D. Ma, G. Pu, C. Lei, L. Ma, H. Wang, Y. Guo, J. Chen, Z. Du, G. Li, H. Ye and B. Liu. Isolation and characterization of AaWRKY1, an Artemisia annua transcription factor that regu- lates the amorpha-4,11-diene synthase gene, a key gene of arte- misin in biosynthesis. Plant and Cell Physiology, 2009, 50(12): 2146-2161.