Genome-wide characterization and expression analysis of MYB transcription factors in Lotus japonicas and Medicago truncatula

MYB is one of the most abundant families of plant transcription factors (TFs), and is involved in plant growth and development regulation, abiotic stress tolerance, hormone signal transduction, and disease resistance. Previously, few genome-wide assays have been conducted in Lotus japonicas and Medicago truncatula. Here, with the recent release of the genome sequences, we performed genome-wide study of MYB TFs in both, including family characterization, evolution and expression analysis. In this study, we totally identified 104 and 166 MYB genes in L. japonicas and M. truncatula, respectively. All these MYB genes were categorized into 261 R2R3-MYBs, 7 R1R2R3-MYBs and 2 atypical MYB genes. This result showed that the majority (96.7%) of them belong to the R2R3-MYB subfamily in both species. Based on phylogenetic analysis, MYB transcription factors were divided into 14 subgroups. MYB genes in four typical branches indicated species-specific expansions in M. truncatula. The exon numbers and conserved motifs associated with MYB domains were also characterized. Furthermore, gene expression analysis performed in various organs showed diverged expression profiles of most MYB genes, suggesting their potential roles in regulating organ growth and development in L. japonicas and M. truncatula.