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

Abstract

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), CH4ʹGT(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.