Characterization of the MADS-Box Gene Family in <i>Akebia trifoliata</i> and Their Evolutionary Events in Angiosperms.

As the largest clade of modern plants, flower plants have evolved a wide variety of flowers and fruits. MADS-box genes play key roles in regulating plant morphogenesis, while basal eudicots have an evolutionarily important position of acting as an evolutionary bridge between basal angiosperms and core eudicots. <i>Akebia trifoliata</i> is an important member of the basal eudicot group. To study the early evolution of angiosperms, we identified and characterized the MADS-Box gene family on the whole-genome level of <i>A. trifoliata</i>. There were 47 MADS-box genes (13 type I and 34 type II genes) in the <i>A. trifoliata</i> genome; type I genes had a greater gene length and coefficient of variation and a smaller exon number than type II genes. A total of 27 (57.4%) experienced whole or segmental genome duplication and purifying selection. A transcriptome analysis suggested that three and eight genes were involved in whole fruit and seed development, respectively. The diversification and phylogenetic analysis of 1479 type II MADS-box genes of 22 angiosperm species provided some clues indicating that a γ whole genome triplication event of eudicots possibility experienced a two-step process. These results are valuable for improving <i>A. trifoliata</i> fruit traits and theoretically elucidating evolutionary processes of angiosperms, especially eudicots.