Abstract:

The paper aims to study the function of the key enzyme geraniol synthase in the terpenoids pathway in Swertia mussotii, a tibetan medicine, and to explore its role in the biosynthesis of geraniol, swertiamarin and gentianaceae. RNA was extracted from leaves of S. mussotii and converted into cDNA. According to the transcriptom of S. mussotii, we cloned the geraniol synthase of S. mussotii by RT-PCR and named SmGES gene. The SmGES gene fragment was connected to the prokaryotic expression vector pET-28a and transformed into the Escherichia coli Rosetta(DE3) for induction expression. According to bioinformatics analysis, the length of SmGES gene was 1761 bp and 586 amino acids were encoded. The isoelectric point of SmGES protein was 5.35 and the relative molecular weight was 67.78 kDa. Analysis showed that SmGES gene contained chloroplast transporter, which was predicted to be a hydrophilic protein located in chloroplast. The intracellular localization, structural domains, secondary and tertiary structures of the protein were analyzed. The results showed that SmGES gene was closely related to GES gene of Gentinan rigescens. The recombinant protein with a molecular weight of 67.78 kDa was induced, which was consistent with the expected size. The study could lay a foundation for further elucidate the synthetic pathway of terpenoids in the S. mussotii.

Key words: Swertia mussotii, geraniol synthase gene, gene cloning, bioinformatics analysis, expression analysis