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Chaihu, the dried roots of some species of Bupleurum L., is a famous Chinese herbal medicine for treatment of liver‐ and cold‐related diseases, in which saikosaponins (SSs) are the major active compounds. Many of the genetic components upstream of SS biosynthetic pathways have been characterized; however, the regulatory mechanisms remain elusive. In this study we identified the APETALA2/Ethylene Responsive Factor family transcription factor gene BcERF3 from B. chinense. The expression of BcERF3 was induced in methyl‐jasmonate‐treated adventitious root of B. chinense; it was also expressed at higher levels in roots than in other tissues (stem, leaf, flower, and tender fruit of early fruiting plants). Transient expression of BcERF3 in the leaves of Nicotiana benthamiana resulted in intracellular localization of the protein in the nucleus. It was also demonstrated that the number of SSs was greater in BcERF3‐overexpressing hairy roots of B. chinense than in plants treated with empty vector controls. This coincided with upregulation of β‐AS, which encodes a key enzyme involved with triterpenoid biosynthesis. In conclusion, BcERF3 plays a positive regulatory role in the biosynthesis of SSs.

Background Monochasma savatieri is a medicinal root hemiparasitic herb that extracts water and nutrients from the host plant via a haustorium. M. savatieri exhibits an enhanced growth after the establishment of parasite-host associations, but little is known about the molecular mechanism responsible. In this study, endogenous hormones, RNA sequencing and small RNA sequencing analysis were performed on M. savatieri before and after establishment of parasite-host associations. Results When grown with the host, decreased contents of jasmonic acid (JA) and indole-3-acetic acid (IAA) and increased abscisic acid (ABA) content were observed in M. savatieri with the established parasitic relationship. When grown with the host, 46,424 differentially expressed genes (DEGs) and 162 differentially expressed miRNAs (DEmiRs) were identified in the comparison between M. savatieri with the established parasitic relationship and without the established parasitic relationship. Analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that these DEGs and targets of DEmiRs mostly participated in plant hormone signal transduction, starch and sucrose metabolism, carbohydrate metabolism, cell growth and death, and transport and catabolism. Furthermore, correlation analysis of mRNA and miRNA revealed that 10 miRNA-target pairs from novel_mir65, novel_mir40, novel_mir80, miR397-5p_1, novel_mir36, novel_mir25 and novel_mir17 may have important roles in regulating the parasitic development of M. savatieri. Conclusions Our study not only expands the understanding of enhanced growth in M. savatieri after the establishment of parasite-host associations, but also first provides abundant resources for future molecular and genetic studies in M. savatieri.

Radix Bupleuri (Chaihu in Chinese) is a traditional Chinese medicine commonly used to treat colds and fevers. The root metabolome and transcriptome of two cultivars of B. chinense (BCYC and BCZC) and one of B. scorzonerifolium (BSHC) were determined and analyzed. Compared with BSHC, 135 and 194 differential metabolites were identified in BCYC and BCZC, respectively, which were mainly fatty acyls, organooxygen metabolites. A total of 163 differential metabolites were obtained between BCYC and BCZC, including phenolic acids and lipids. Compared with BSHC, 6557 and 5621 differential expression genes (DEGs) were found in BCYC and BSHC, respectively, which were annotated into biosynthesis of unsaturated fatty acid and fatty acid metabolism. A total of 4,880 DEGs existed between the two cultivars of B. chinense. The abundance of flavonoids in B. scorzonerifolium was higher than that of B. chinense, with the latter having higher saikosaponin A and saikosaponin D than the former. Pinobanksin was the most major flavonoid which differ between the two cultivars of B. chinense. The expression of chalcone synthase gene was dramatically differential, which had a positive correlation with the biosynthesis of pinobanksin. The present study laid a foundation for further research on biosynthesis of flavonoids and terpenoids of Bupleurum L.

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