Evolution and functional divergence of MADS-box genes in Pyrus

Abstract

Abstract MADS-box transcription factors widely regulate all aspects of plant growth including development and reproduction. Although the MADS-box gene family genes have been extensively characterized in many plants, they have not been studied in closely related species. In this study, 73 and 74 MADS-box genes were identified in European pear ( Pyrus communis ) and Chinese pear ( Pyrus bretschneideri ), respectively. Based on the phylogenetic relationship, these genes could be clustered into five groups (Mα, Mβ, Mr, MIKC C , MIKC*) and the MIKC C group was further categorized into 10 subfamilies. The distribution of MADS-box genes on each chromosome was significantly nonrandom. Thirty-seven orthologs, twenty-five PcpMADS ( P . communis MADS-box) paralogs and nineteen PbrMADS ( P . bretschneideri MADS-box) paralogs were predicted. Among these paralogous genes, two pairs arose from tandem duplications (TD), nineteen from segmental duplication (SD) events and twenty-three from whole genome duplication (WGD) events, indicating SD/WGD events led to the expansion of MADS-box gene family. The MADS-box genes expression profiles in pear fruits indicated functional divergence and neo-functionalization or sub-functionalization of some orthologous genes originated from a common ancestor. This study provided a useful reference for further analysis the mechanisms of species differentiation and biodiversity formation among closely related species.