Comparison of the transcriptomes and expression patterns of genes involved in key medicinal secondary metabolites from Astragalus membranaceus and Astragalus membranaceus var. mongholicus

Radix astragali, from the roots of Astragalus L. species, is regarded as an important traditional medicinal plant and has been widely used as a Qi-Invigorating medicine for more than 2 000 years. Considering the different metabolites or functional compounds of Radix astragali from distinct species, the underlying genetic information among the two species is important. Here, we compared the two different root transcriptomes and expression patterns of genes involved in key medicinal secondary metabolites of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao and Astragalus membranaceus (Fisch.) Bge. A total of 98 017 578 and 102 635 956 reads, including 98 294 560 and 92 494 416 high-quality reads, were obtained for A. mongholicus and A. membranaceus, respectively. In general, 73 785 (39.47%) and 60 739 (34.93%) unigenes for A. mongholicus and A. membranaceus were differentially expressed, indicating that the two species had many homologous genes. In comparison, the carbon metabolism category contained the most abundant unigenes in A. mongholicus, and it contained many more genes than those found in A. membranaceus based on the KEGG results. Genes that may participate in the biosynthesis of flavonoids, diterpenoids, triterpenoids, steroids, isoquinoline alkaloids, and carotenoids, such as CHS, F3H, GA3, and CYPs, were identified based on annotations. A total of 5 227 and 5 101 transcription factors (TFs) were identified in A. mongholicus and A. membranaceus, respectively. Three TF categories were found and showed twice as many numbers for A. mongholicus than A. membranaceus, i.e., SOH1 (4:2), LIM (18:5), and GRF (19:5), while MED7 had more unigenes in A. membranaceus (6:12). These results indicated that the different pathways may be involved in the synthesis of active ingredients in the two germplasm resources, and the data obtained will provide valuable information for further utilization and investigation of these two species.

Automated summary

This study compared the gene expression patterns of two different varieties of radix astragali, and found that they have many homologous genes but differ in different metabolic pathways. By analyzing these genes, valuable information for further development and utilization of these two species of astragalus can be obtained.