Genome-Wide Analysis of MIKCC-Type MADS-Box Genes Reveals Their Involvement in Flower Development in Malus Lineage

Abstract

MIKCC-type MADS-box genes are involved in floral organ identity determination but remain less studied in the Malus lineage. Based on the conserved domains of this gene family, we identified 341 genes among 13 species. Classification results showed that the MIKCC-type were generated later than the M-type, after the formation of Chlamydomonas reinhardtii. By phylogenetic analysis, three different groups were divided among 12 plant species, and one group was an ancestral MIKCC-type MADS-box homologous gene cluster from lower moss to higher flowering plants. Comparative analysis of these genes in A. thaliana and Malus lineages revealed a similar pattern evolutionary relationship with the phylogenetic analysis. Three classes of genes of the ABC model in A. thaliana had orthologous genes in the Malus species, but they experienced different evolutionary events. Only a whole-genome duplication (WGD) event was considered to act on the expansion of ABC-model-related genes in the Malus lineage. Additionally, the expression pattern of genes showed to be involved in flowering development stages and anther development processes among different M. domestica cultivars. This study systematically traced the evolutionary history and expansion mechanism of the MIKCC-type MADS-box gene family in plants. The results also provided novel insights for ABC model research of flower development in the Malus lineage.