A 1 539 bp squalene synthase (AaSQS) cDNA was cloned from a high_yield Artemisia annua L. strain 001 by reverse transcription_polymerase chain reaction (RT_PCR). The amino acid sequence of AaSQS is 70%, 77%, 44% and 39% identical to that of squalene synthases from Arabidopsis thaliana , tobacco, human and yeast, respectively. The AaSQS genomic DNA has a complex organization containing 14 exons and 13 introns. Full_length or C_terminal truncated cDNA was subcloned into prokaryotic expression vector pE...