Objective:To clone the full-length cDNA of 3-hydroxy-3-methylglutaryl CoA reductase(HMGR) gene from Gentiana rigescens

construct prokaryotic expression vector for expression in Escherichia coli

quantify the expressions and conduct bioinformatics analysis. Method:Polymerase chain reaction (PCR) technique was used for cloning the cDNA sequence of HMGR from G. rigescens. The pEASY-E1-HMGR expression vector was constructed to prokaryotic expression and the expression was induced by isopropyl β-D-thiogalactoside (IPTG). The obtained cDNA sequences were analyzed and their structure and function were forecasted by bioinformatics method. The expression levels of HMGR gene of roots

stems and leaves in different growth stages were analyzed by using Real-time quantitative PCR (Real-time PCR) in G. rigescens. Result:Two groups of HMGR gene were cloned

one group of HMGR cDNA full-length was 1 747 bp

open reading frame (ORF) of 1 697 bp

encoding 565 amino acids

named as GRHMGR-1;another group of HMGR cDNA full-length was 1 731 bp

ORF of 1 572 bp

encoding 523 amino acids

and named as GRHMGR-2. SDS-PAGE showed that the recombinant plasmid could successfully express the target proteins. Blastp found that GRHMGR-1 and GRHMGR-2 were closely related to the same genus plants G. lutea and G. macrophylla. The structure analysis results showed that both of them contained two HMG-CoA binding sites and two NADPH binding sites

implying that it may be localized on endoplasmic reticulum. RT-PCR showed that HMGR gene was expressed in roots

stems and leaves at four different growth stages

and the highest expression level was found in leaves. Conclusion:This was the first time to obtain cloned HMGR genes from G. rigescens. The results can provide a foundation for exploring the mechanism of gentiopicroside biosynthesis in G. rigescens.