Cloning, Yeast Expression, and Characterization of a ß-Amyrin C-28 Oxidase (CYP716A249) Involved in Triterpenoid Biosynthesis in Polygala tenuifolia.

Polygala tenuifolia Willd. is a traditional Chinese herbal medicine that is widely used in treating nervous system disorders. Triterpene saponins in P. tenuifolia (polygala saponins) have excellent biological activity. As a precursor for the synthesis of presenegin, oleanolic acid (OA) plays an important role in the biosynthesis of polygala saponins. However, the mechanism behind the biosynthesis of polygala saponins remains to be elucidated. In this study, we found that CYP716A249 (GenBank: ASB17946) oxidized the C-28 position of ß-amyrin to produce OA. Using quantitative real-time PCR, we observed that CYP716A249 had the highest expression in the roots of 2-year-old P. tenuifolia, which provided a basis for the selection of samples for gene cloning. To identify the function of CYP716A249, the strain R-BE-20 was constructed by expressing ß-amyrin synthase in yeast. Then, CYP716A249 was co-expressed with ß-amyrin synthase to construct the strain R-BPE-20 by using the lithium acetate method. Finally, we detected ß-amyrin and OA by ultra-HPLC-Q Exactive hybrid quadrupole-Orbitrap high-resolution accurate mass spectrometry and GC-MS. The results of this study provide insights into the biosynthesis pathway of polygala saponins.

[Analysis of influencing factors of secondary metabolites contents in cultivated Polygala tenuifolia].

This work was launched to explore the effect of habitat and growth year on the secondary metabolites contents of cultivated Polygala tenuifolia. The samples of cultivated P. tenuifolia were analyzed by ultra-high performance liquid chromatography(UPLC)-quadrupole time-of-flight mass spectrometry(Q-TOF MS), and the obtained data were analyzed using multiple statistical analysis and cluster analysis. The results showed that compared with growth year, habitat is a main influencing factor which affected the secondary metabolites contents of P. tenuifolia. The contents of sucrose esters and oligosacchride multi-esters are greatly dependent on the habitat (the sample-AG with high levels of components of tenuifoliside B and tenuifoliside C, and the sample-FY with high levels of 3,6'-disinapoyl sucrose, tenuifoliose S, tenuifoliose L, and tenuifoliose V). There is no obvious effect of habitat and growth year on xanthone. The contents of triterpene saponins are greatly dependent on the growth year, and the content of parts of triterpene saponins increased as time goes on.The result indicated that the effect of habitat and growth year on different types of secondary metabolites is not completely equivalent. This study will contribute to the breeding of P. tenuifolia and amendment of current commodity criteria.

Utilization of UPLC/Q-TOF-MS-Based Metabolomics and AFLP-Based Marker-Assisted Selection to Facilitate/Assist Conventional Breeding of Polygala tenuifolia.

As one of the most important traditional Chinese medicine, the quality of Polygala tenuifolia is difficult to control and a new method must be established to facilitate/assist the breeding of P. tenuifolia. In this study, UPLC/Q-TOF-MS-based metabolomics analysis was performed to determine the chemical composition and screen metabolite biomarkers according to agronomic traits. A total of 29 compounds and 18 metabolite biomarkers were found. AFLP-based marker-assisted selection (MAS) was used to identify molecular marker bands and screen characteristic bands associated with specific agronomic traits. 184 bands and 76 characteristic AFLP bands were found. The correlation network between compounds and characteristic AFLP bands was built, so we may directly breed certain P. tenuifolia herbs with special agronomic traits (or characteristic AFLP bands), which exhibit specific pharmacological functions depending on the content of the active compounds. The proposed method of metabolomics coupled with MAS could facilitate/assist the breeding of P. tenuifolia.