Flavonoid Biosynthesis Genes in Triticum aestivum L.: Methylation Patterns in Cis-Regulatory Regions of the Duplicated CHI and F3H Genes

Tissue-specific transcriptome analyses unveils candidate genes for flavonoid biosynthesis, regulation and transport in the medicinal plant Ilex asprella

It is not clear that the genes involved with flavonoids synthesis, regulation and transport in Ilex asprella. Transcriptome analysis of leaf, stem and root has uncovered 28,478 differentially expressed genes (DEGs) that are involved in various biological processes. Among these, the expression of 31 candidate synthetase genes, 19 transcription factors, and 5 transporters associated with flavonoid biosynthesis varies across tissues, encompassing seven complete biosynthetic pathways (stilbene, aurone, flavone, isoflavone, flavonol, phlobaphene, and anthocyanin) and one partial pathway (proanthocyanidin). Tissue-specific expression patterns suggest that the stilbenes, aurones, flavones and anthocyanin branches are more prominent in roots, as indicated by key genes such as STS(Ilex_044726), CH4'GT(Ilex_047989), FNS(Ilex_043640) and UFGT(Ilex_014720). In leaves, the phlobaphenes and flavonols branches are dominant, determined by CHI(Ilex_005941), FNR(Ilex_039777) and FLS(Ilex_046424). The isoflavone pathway appears to be more active in stems due to the presence of IFS(Ilex_029360), mirroring the accumulation of the intermediate metabolite chalcone, which is regulated by CHS(Ilex_047537). The absence of LAR genes implies that gallocatechin, and catechin liked proanthocyanidins cannot be synthesized in I. asprella. Meanwhile, the general phenylpropanoid pathway is more active in roots, stems than in leaves, as evidenced by the expression of PAL(Ilex_042231, Ilex_014816), C4H(Ilex_017598), and 4CL(Ilex_042033). Flavanone, dihydroflavonol and leucoanthocyanidin, key intermediates, accumulate more rapidly in stem, stem and root, respectively, regulated by CHI(Ilex_005941), F3H(Ilex_004635) and DFR(Ilex_004771). Correlation and network analyses reveal that candidate regulators and transporters are closely associated with the synthesis genes. The study provides profound snoop into flavonoids metabolism in I. asprella and offers valuable refer for medicinal plant.

Phylogenetic Analysis of R2R3-MYB Family Genes in Tetrastigma hemsleyanum Diels et Gilg and Roles of ThMYB4 and ThMYB7 in Flavonoid Biosynthesis

Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is an extensively used Chinese folk herb with multiple bioactivities. Among these bioactivities, flavonoids are recognized as the representative active ingredients. We previously found an elevated accumulation of flavonoids in T. hemsleyanum under water stress; however, the mechanism remains unclear. R2R3-MYB transcription factors play vital roles in the plant response to environmental stress and the regulation of secondary metabolites. Herein, a systematic transcriptome identification of R2R3-MYB family genes under water stress in T. hemsleyanum was performed to explore their potential function in the biosynthesis of flavonoids. A total of 26 R2R3-MYB genes were identified, most of which were clustered into functional branches of abiotic stress. ThMYB4 and ThMYB7 were then screened out to be associated with the biosynthesis of flavonoids through a protein-protein interaction prediction. An expression correlation analysis based on RNA-seq further confirmed that ThMYB4 and ThMYB7 were positively related to the flavonoid biosynthetic pathway genes of T. hemsleyanum. In ThMYB4- and ThMYB7-overexpression hairy roots, it was found that the expression of ThCHS and ThCHI was significantly increased, suggesting that ThMYB4 and ThMYB7 may act as regulators in flavonoid biosynthesis. This will shed new light on the promotion of flavonoid production and the medicinal value of T. hemsleyanum by manipulating transcription factors.