Fig. 7.

A proposed model for the evolution of the ICK/KRP family. Based on sequence similarity and exon–intron organization, ICK/KRP genes are grouped into three major classes. While genes in the C-class have three exons, genes in the A- and B-classes have four exons. The C-class contains members from dicotyledons, monocotyledons and gymnosperms, suggesting a common ancestral class before the emergence of angiosperm plants. The A- and B- classes have only members from dicotyledons and monocotyledons, respectively, suggesting their split before the speciation of these two groups of plants. The number of family members increased through more recent segmental duplications in the plant genomes. Circles describe dated duplication events according to the literature. Potential origins for the Os01g37740 are marked with dotted lines. See text for more details.