<i>De novo</i> transcriptomic analysis to reveal functional genes involved in triterpenoid saponin biosynthesis in <i>Oplopanax elatus</i> NAKAI

Oplopanax elatus is a valuable medicinal plant in the family Araliaceae that recommends itself as source of herbal preparations. Although, as in ginseng, triterpenoid saponins make up the major bioactive component of O. elatus, nothing is known about the genes that are involved in the biosynthesis of these complex compounds, as reflected also by a lack of genomic information in public databases. Using Illumina paired-end sequencing technology, we have therefore generated a transcriptome library of O. elatus from a pooled RNA sample from different organs. 208,959 unigenes were assembled from approximately 77 million high-quality reads, and 110,202 unigenes (52.7% of the unigenes) were annotated. In addition, 47,273 cDNA-derived SSRs in 38,446 unigenes were identified as potential molecular markers. Furthermore, 122 unigenes encoding 47 putative enzymes related to the biosynthesis of the backbone of triterpenoid saponins were identified by analyzing our library. The organ-specific expression of selected genes suggests that the leaves of O. elatus are the main site of triterpenoid saponin biosynthesis. The transcriptome data reported here provides valuable and comprehensive information for further research into the metabolic pathways of O. elatus as well as into genetic variation in the Oplopanax genus. The online version of this article (doi: 10.5073/JABFQ.2017.090.004) contains supplementary files