Identification, 3D modelling, and expression analysis of protopanaxadiol and protopanaxatriol synthases in Vietnamese ginseng under vanadium elicitation

Vietnamese ginseng (Panax vietnamensis Ha & Grushv.) is one of the most precious herbs in Vietnam because it contains many valuable bioactive compounds, especially ginsenosides. The protopanaxadiol synthase (PPDS) and protopanaxatriol synthase (PPTS) are considered the key enzymes for the ginsenoside biosynthesis pathway in Panax species. This study is the first report on the PPDS and PPTS genes and their enzymes in Vietnamese ginseng (named PvH_PPDS and PvH_PPTS, respectively). Two PvH_PPDS and PvH_PPTS genes contain 345 aa and 736 aa, respectively, with a common structure of 3 exons and 2 introns. The domain CYP450, which is conserved and essential for catalytic activity in the cytochrome P450 family, was detected in both of these genes. Their 3D protein structures were homology-modeled and annotated by bioinformatics tools. The phylogenetic tree shows that the PvH_PPDS and PvH_PPTS genes differ in their level of similarity with the corresponding genes of other Panax species. The elicitation of vanadium compounds improved the expression level of PvH_PPDS and PvH_PPTS genes as well as the accumulation of dammarane-type major ginsenosides in adventitious roots of Vietnamese ginseng. The present work is the first attempt to further understand two key enzymes in the biosynthesis of ginsenosides in this medicinal herb