Biosyntheses characterization of alkaloids and flavonoids in Sophora flavescens by combining metabolome and transcriptome

Abstract

Sophora flavescens are widely used for their pharmacological effects. As its main pharmacological components, alkaloids and flavonoids are distributed in the root tissues wherein molecular mechanisms remain elusive. In this study, metabolite profiles are analyzed using metabolomes to obtain biomarkers detected in different root tissues. These biomarkers include alkaloids, phenylpropanoids, and flavonoids. The high-performance liquid chromatography analysis results indicate the differences in principal component contents. Oxymatrine, sophoridine, and matrine contents are the highest in the phloem, whereas trifolirhizin, maackiain, and kushenol I contents are the highest in the xylem. The transcript expression profiles also show tissue specificity in the roots. A total of 52 and 39 transcripts involved in alkaloid and flavonoid syntheses are found, respectively. Among them, the expression levels of LYSA1, LYSA2, AO2, AO6, PMT1, PMT17, PMT34, and PMT35 transcripts are highly and positively correlated with alkaloids contents. The expression levels of 4CL1, 4CL3, 4CL12, CHI5, CHI7, and CHI9 transcripts are markedly and positively correlated with flavonoids contents. Moreover, the quantitative profiles of alkaloids and flavonoids are provided, and the pivotal genes regulating their distribution in S. flavescens are determined. These results contribute to the existing data for the genetic improvement and target breeding of S. flavescens.

Figure 1

Metabolomic analysis of the components in the root tissues of S. flavescens. (a) PCA score plots of positive ion mode. (b) One-way ANOVA of the positive ion mode. (c) Variable importance in the projection of positive ion mode. (d) PCA score plots of negative ion mode. (e) One-way ANOVA of negative ion mode. (f) Variable importance in the projection of negative ion mode.

Figure 2

Contents of alkaloids and flavonoids in the root tissues of S. flavescens. (a) Contents of three alkaloids. (b) Contents of five flavonoids. Pe, Ph, and Xy represent the periderm, phloem, and xylem, respectively.

Figure 3

(a) Principal component analysis (PCA) and (b) Venn profiles in the roots of S. flavescens.

Figure 4

Co-expression profiles of all transcripts and active components in the root tissues of S. flavescens. (a) Hierarchical cluster tree showing co-expression modules in S. flavescens. (b) Module-components association in S. flavescens.

Figure 5

Heatmap of transcripts involved in the (a) alkaloid and (b) flavonoid biosyntheses in the roots of S. flavescens.

Figure 6

Pearson correlation bubble chart of the transcript expression and chemical component contents in S. flavescens: (a) alkaloids and (b) flavonoids. The size of the circle represents the correlation coefficient. The color red represents a positive correlation, whereas the color green represents a negative correlation.