Identification and expression analysis of SQUAMOSA promoter-binding protein ( SBP ) genes in mungbean

SQUAMOSA promoter-binding protein ( SBP ) genes are important transcription factors involved in plant growth and development. However, the information about mungbean VrSBP genes is limited. In this study, we identified and characterized 22 VrSBP genes in the mungbean genome. Many characteristics of VrSBP genes were analyzed, and most VrSBP genes were considered to be expressed only in the nucleus. VrSBP genes were grouped into 9 subfamilies, with the exception of the g7 and ms subfamilies which are distinctive to Poaceae species. The g3 subfamily was the largest one with 6 VrSBP members. Eight segmental events were found among VrSBP genes, and all VrSBP duplicated genes were evolved via purification selection. The gene structure of VrSBP genes in the same subfamily was similar, and the conserved motifs are different among different subfamilies of VrSBP genes. Additionally, 12 VrSBP genes were considered to be the target genes of vra-miR156a. The types and numbers of cis -acting elements in VrSBP promoters were varied and VrSBP genes showed different expression patterns in different tissues. In addition, the protein interaction network revealed that VrSBP genes were involved in many development processes. Our study has provided important information which will allow the further functional characterization of VrSBP genes.