Comparison of root transcriptomes and expressions of genes involved in main medicinal secondary metabolites from Bupleurum chinense and Bupleurum scorzonerifolium, the two Chinese official Radix bupleuri source species

Radix bupleuri, roots of Bupleurum species, is a widely used traditional Chinese medicine. Here, we compared the root transcriptomes of both Bupleurum chinenseDC. and Bupleurum scorzonerifolium Willd. A total of 313 483 and 342 263 high quality expressed sequence tags were obtained, respectively. In addition, 17 117 (59.2%) and 19 416 (62.8%) unigenes for B. chinense and B. scorzonerifolium had homologous genes in the opposite dataset. For B. chinense, Kyoto Encyclopedia of Genes and Genomes database (KEGG) annotation identified carbohydrate metabolism, energy metabolism and amino acid metabolism as the three highest groups in the metabolism category. For B. scorzonerifolium, the lipid metabolism group had the most unigenes. Genes that may participate in the biosynthesis of terpenoid, triterpenoid, sterol, lignan and flavonoids were identified according to their annotations. (Tri)terpenoid-related genes were predominantly found in B. chinense. The expressions of certain genes were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in the roots of the two species. A total of 558 putative transcription factors (TFs) and 137 transcriptional regulators (TRs) among 1364 TFs and 327 TRs, and 610 TFs and 129 TRs among 1600 TFs and 323 TRs were specific for B. chinense and B. scorzonerifolium, respectively. Our transcriptome comparison reflects the different types and proportions of metabolites synthesized by the two species. The data, especially, those genes involved in the biosynthesis of particular types of metabolites, will provide the basis for further investigations of the secondary metabolite repertoire of the two Bupleurum species, as well as other species from the genus of Bupleurum.