Abstract: Abstract：Squalene synthase（EC.2.5.1.21, SS）is an important key enzyme in biosynthesis pathway of plant sterols and terpenoids. In order to learn the role of SS in the biosynthesis of saikosaponin in Bupleurum chinense DC., SS cDNA was cloned with total RNA extracted from adventitious roots of B. chinense using Trizol method. Specific fragments were amplified by RT-PCR and then were cloned and sequenced. Sequencing results showed two different cDNA fragments（BcSS1 and BcSS2）with 1 245 bp and 1 248 bp long were obtained which encodes proteins with 414 and 415 amino acids, respectively. The identities of nucleotides and amino acids between BcSS1 and BcSS2 were 98% and 96%. NCBI Blastx search results showed BcSS1 and BcSS2 had the highest amino acid similarity to the corresponding proteins from B.falcatum L. and Panax notoginseng F. H. Chen. The identities of BcSS1 with the two proteins were 99 % and 90% and those of BcSS2 were 97% and 87%. SS gene with 5 880 bp containing 12 introns was then amplified by PCR with genomic DNA extracted from adventitious roots of B. chinense using CTAB method.

Key words: Bupleurum chinense DC., saikosaponin, squalene synthase gene（SS）, RT-PCR, PCR