Transcriptome-based identification of MYB transcription factors associated with flavonoid biosynthesis under LED light in Astragalus membranaceus (Fisch.) Bunge

Astragalus membranaceus, valued for its health benefits due to flavonoids, saponins, and polysaccharides, has been studied mainly for its roots. However, the regulatory role of MYB transcription factors (TFs) in flavonoid biosynthesis under different light conditions remains largely unexplored. In this study, sterile plants were cultured for six weeks under white, red, and blue light. Transcriptome analysis identified MYB genes, which were further characterized by sequence alignment, conserved domain searches, and phylogenetic analysis with AtMYB and GmMYB176. Gene structures, conserved motifs, and cis-regulatory elements were examined using bioinformatics tools. Expression levels of selected genes were validated by real-time PCR using the 2−ΔΔCt method. Two candidate genes, one R2R3-MYB and one R1-MYB, were found to be involved in flavonoid biosynthesis. Both showed high expression under white light, with AmMYB12 exhibiting nearly 20-fold higher expression compared with other conditions. Motif and promoter analyses indicated the presence of multiple MYB-binding sites, suggesting strong regulatory potential. Together, these results indicate that AmMYB12 may play a critical role in light-regulated flavonoid biosynthesis. This study provides essential data for functional analysis of MYB TFs and enhances understanding of molecular mechanisms underlying flavonoid accumulation in A. membranaceus in response to artificial light.