Full-Length Transcriptome Sequences by A Combination of Sequencing Platforms Applied to Isoflavonoid and Triterpenoid Saponin Biosynthesis of Astragalus Mongholicus Bunge

Abstract Background: Astragalus mongholicus Bunge is an important medicinal plant and has been used in traditional Chinese medicine for a long history, which is rich in isoflavonoids and triterpenoid saponins. Although these active constituents in A. mongholicus have been discovered for a long time, the molecular genetic basis of the isoflavonoid and triterpenoid saponin biosynthesis pathways is virtually unknown due to the lack of a reference genome. The combination of next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing to analyze genes involved in the biosynthetic pathways of secondary metabolites in medicinal plants has been widely recognized.Results: In this study, NGS, SMRT sequencing, and targeted compounds were combined to investigate the association between isoflavonoids and triterpenoid saponins and gene expression in roots, stems and leaves of A. mongholicus. A total of four main isoflavonoids and four astragalosides (belong to triterpenoid saponins) were measured, and 44 differentially expressed genes (DEGs) of nine gene families, 44 DEGs of 16 gene families that encode for enzymes involved in isoflavonoid and triterpenoid saponin biosynthesis were identified, separately. Additionally, transcription factors (TFs) associated with isoflavonoid and triterpenoid saponin biosynthesis were analyzed, including 72 MYBs, 53 bHLHs, 64 AP2-EREBPs and 11 bZIPs. The above transcripts exhibit different expression trends in different organs.Conclusions: Our study provides important genetic information for the essential genes of isoflavonoid and triterpenoid saponin biosynthesis in A. mongholicus, and provides a basis for developing its medicinal value.