[Dead heart of pith-decayed Scutellariae Radix: a study based on multi-omics]

Dead heart is an important trait of pith-decayed Scutellariae Radix. The purpose of this study was to clarify the scientific connotation of the dead heart using multi-omics. Metabolomics and transcriptomics combined with multivariate statistical analysis such as principal component analysis(PCA) and partial least squares discriminant analysis(PLS-DA) were used to systematically compare the differences in chemical composition and gene expression among phloem, outer xylem and near-dead xylem of pith-decayed Scutella-riae Radix. The results revealed significant differences in the contents of flavonoid glycosides and aglycones among the three parts. Compared with phloem and outer xylem, near-dead xylem had markedly lowered content of flavonoid glycosides(including baicalin, norwogonin-7-O-β-D-glucuronide, oroxylin A-7-O-β-D-glucuronide, and wogonoside) while markedly increased content of aglycones(including 3,5,7,2',6'-pentahydroxy dihydroflavone, baicalin, wogonin, and oroxylin A). The differentially expressed genes were mainly concentrated in KEGG pathways such as phenylpropanoid metabolism, flavonoid biosynthesis, ABC transporter, and plant MAPK signal transduction pathway. This study systematically elucidated the material basis of the dead heart of pith-decayed Scutellariae Radix with multiple growing years. Specifically, the content of flavonoid aglycones was significantly increased in the near-dead xylem, and the gene expression of metabolic pathways such as flavonoid glycoside hydrolysis, interxylary cork development and programmed apoptosis was significantly up-regulated. This study provided a theoretical basis for guiding the high-quality production of pith-decayed Scutellariae Radix.