Genome-wide identification and expression analysis of the MYB transcription factor family in Desmodium styracifolium

The aerial parts of Desmodium styracifolium are widely used in traditional Chinese medicine to treat urinary calculi, with flavonoids as the primary active components. MYB transcription factors are key regulators of flavonoid biosynthesis in plants; however, the MYB family of D. styracifolium has not yet been systematically investigated.

Using previously obtained whole-genome and transcriptome data, DsMYB genes were identified through combined hmmsearch and blastp screening. Phylogenetic relationships were reconstructed together with 131 Arabidopsis thaliana MYB proteins. Chromosomal localization, collinearity, conserved motifs, gene structure, and promoter cis-acting elements were analyzed. Expression patterns across tissues and under high-light treatment were profiled, and eight representative genes were verified by quantitative real-time PCR (qRT-PCR).

A total of 161 DsMYB genes were identified and categorized into R2R3-MYB (134), 1R-MYB (21), 3R-MYB (5), and 5R-MYB (1) subfamilies; 132 genes were unevenly distributed across nine chromosomes, with the remaining 29 located on unplaced scaffolds. Collinearity analysis indicated that segmental duplication was the primary driver of R2R3-MYB expansion. Phylogenetic analysis resolved 25 subgroups, among which the largest subgroup C13 (30 members) was specific to D. styracifolium, and subgroups C20 and C17 corresponded to the Arabidopsis anthocyanin and flavonol regulatory clades, respectively. Most DsMYB proteins shared core conserved motifs 2~5, and their promoters were enriched in light-, abscisic acid-, and methyl jasmonate-responsive elements. Eight qRT-PCR-verified DsMYB genes exhibited tissue-specific expression and distinct induction patterns under high light.

This study provides the first systematic characterization of the MYB family in D. styracifolium. The enrichment of light- and hormone-responsive cis-elements, together with the light-responsive expression of candidate members, implicates DsMYBs in the transcriptional control of flavonoid biosynthesis, with the C17 and C20 subgroups emerging as priority candidates for flavonol and anthocyanin regulation.