MAPKK2/4/5/7-MAPK3-JAZs modulate phenolic acid biosynthesis in Salvia miltiorrhiza.

Phenolic acids are the major bioactive metabolites produced in Salvia miltiorrhiza, a traditional Chinese medicine called Danshen. Many phytohormone elicitor treatments induce phenolic acid biosynthesis, even though the underlying mechanism remains obscure. Expression pattern analysis showed that SmMAPK3 was highly expressed in leaves, and SmMAPK3 was significantly induced by salicylic acid (SA) and methyl jasmonate (JA). Bioinformatics analysis revealed that SmMAPK3 belongs to group A and contains a TEY motif in the activation loop together with three conserved regions (P-loop, C-loop and CD-domain). A previous study speculated that SmMAPK3 is likely a positive regulator in the biosynthesis of phenolic acids in S. miltiorrhiza. In this study, overexpression of SmMAPK3 increased phenolic acid biosynthetic gene expression and enhanced the accumulation of phenolic acids in S. miltiorrhiza plantlets. Yeast two-hybrid (Y2H) analysis and firefly luciferase complementation imaging (LCI) assays revealed that SmMAPKK2/4/5/7-SmMAPK3-SmJAZs form a cascade that regulates the accumulation of phenolic acids. In summary, this work deepens our understanding of the posttranscriptional regulatory mechanisms of phenolic acid biosynthesis and sheds new light on metabolic engineering in S. miltiorrhiza.

Genome-wide characterization and expression profiling of MAPK cascade genes in Salvia miltiorrhiza reveals the function of SmMAPK3 and SmMAPK1 in secondary metabolism.

BACKGROUND: The contribution of mitogen-activated protein kinase (MAPK) cascades to plant growth and development has been widely studied, but this knowledge has not yet been extended to the medicinal plant Salvia miltiorrhiza, which produces a number of pharmacologically active secondary metabolites. RESULTS: In this study, we performed a genome-wide survey and identified six MAPKKK kinases (MAPKKKKs), 83 MAPKK kinases (MAPKKKs), nine MAPK kinases (MAPKKs) and 18 MAPKs in the S. miltiorrhiza genome. Within each class of genes, a small number of subfamilies were recognized. A transcriptional analysis revealed differences in the genes' behaviour with respect to both their site of transcription and their inducibility by elicitors and phytohormones. Two genes were identified as strong candidates for playing roles in phytohormone signalling. A gene-to-metabolite network was constructed based on correlation analysis, highlighting the likely involvement of two of the cascades in the synthesis of two key groups of pharmacologically active secondary metabolites: phenolic acids and tanshinones. CONCLUSION: The data provide insight into the functional diversification and conservation of MAPK cascades in S. miltiorrhiza.

Immunosuppressive C21 steroidal glycosides from the root of Cynanchum atratum.

Six new C21 steroidal glycosides (1-6) and one dideoxysaccharide (7), named atratcynosides A-F and atratcynose A, were isolated from the 80% ethanol extract of the root of Cynanchum atratum, together with three known compounds (8-10). The structures of the new compounds were determined on the basis of extensive spectral analyses and qualitative chemical methods. All compounds were subjected to detect the immunosuppressive activities by an in vitro model of concanavalin A-induced proliferation of T-lymphocytes from mice. Compounds 1-3 showed significant immunosuppressive activities in dose-dependent manners with the IC50 values from 3.3 to 7.0 µM. Moreover, the structure-activity relationship of the steroidal glycosides on the immunosuppression was analyzed.