CLONING AND CHARACTERIZATION OF THREE SQUALENE EPOXIDASE GENES IN PANAX VIETNAMENSIS VAR. FUSCIDICUS

Panax vietnamensis var. fuscidiscus, is a new variety of Panax. vietnamensis, which was first found in Jinping County, the southern part of Yunnan Province, China. It is also one of the most prized medicinal plants used in traditional ethnic minority medicine systems. This species contains higher content of ocotillol-type saponin, especially majonoside R2, which make this plant particularly suitable for identification of the SE genes responsible for the biosynthesis of ginsenosides. Three cDNAs encoding SE were cloned from P. vietnamensis var. fuscidiscus, and their molecular characterizations were investigated. The tissue-specific expression patterns of the three SE genes were analyzed by RT-qPCR. The transcription levels of these genes in Methyl jasmonate (MeJA)-treated leaves of P. vietnamensis var. fuscidiscus were also estimated by RT-qPCR. PvfSE, PvfSE2 and PvfSE3 differed in predicted membrane-spanning helices. Phylogenetic analysis grouped these SE into three different clades. The three PvfSE isoforms were all most highly expressed in leaves. Moreover, they exhibited different response patterns under MeJA induction. The three PvfSE isoforms may play different roles in sterol or ginsenoside biosynthesis in this herb This report is the first attempt to clone and expression analysis of SE from P. vietnamensis var. fuscidiscus and provides a new foundation for further understanding the role of SE in the biosynthesis of ginsenosides.