Comparative analysis and natural evolution of squalene epoxidase in three Fritillaria species.

Fritillariae Bulbus are the most commonly used antitussive and edible herbs in China. Based on UPLC-QTOF-MS and UPLC-QQQ-MS, the validated MRM-based non-targeted quantitative method was applied to determinate the contents of 48 Fritillaria alkaloids (FAs) in three Fritillaria species (F. thunbergii Miq., F. unibracteata and F. ussuriensis). The RNA-Seq results showed that gene transcript levels have different expression patterns in three Fritillaria species. Based on transcriptome data, the full-length cDNA sequences of squalene epoxidase gene were cloned and characterized. Natural evolution of squalene epoxidase genes resulted in four mutations (C236R, M489L, G510A and K517R) in three Fritillaria species. Molecular docking analysis showed that the 236 residue is located inside the pocket and the binding center while other three residues are located on the surface of the protein. Functional verification indicated the mutations of SQE (C236R) could effectively increase the activity of SQE and obtain higher yield of 2,3-oxidosqualene in recombinant yeast. And the mutations of SQE (M489L and G510A), which increased the hydrophobicity of the protein surface, could also enhance the activity of SQE. This study provides major insights into the metabolites differentiation of FAs biosynthesis, and a firm foundation for the quality control and metabolic engineering of Fritillariae bulbus.

A metabolomic strategy based on integrating headspace gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry to differentiate the five cultivars of Chrysanthemum flower.

The extreme complexity of the chemical composition of plant extracts requires an unbiased and comprehensive detection methodology to improve the potential of metabolomic study. The present work, taking five closely related cultivars of Chrysanthemum flowers as a typical case, attempts to develop a metabolomic strategy to find more markers of metabolites for precise differentiation based on headspace gas chromatography-mass spectrometry (HSGC-MS) and ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS). In detail, 53 batches of Chrysanthemum flower samples were collected and analyzed. The fusion of datasets from HSGC-MS and UHPLC-QTOF/MS was done in two different ways. After comparison, the fusion of the total peak area normalized metabolomic data was performed for multivariate statistical analysis. A total of 21 marker compounds (including 14 volatile and 7 nonvolatile metabolites) were identified, and a heatmap was employed for clarifying the distribution of the identified metabolites among the five cultivars. The results indicated that the integrated platform benefited the metabolomic study of medicinal and edible herbs by providing complementary information through fully monitoring functional constituents.