Figure 4

Phylogenetic tree derived from selected 20 IRK AA sequences. To show the major phylogenetic evolution of IRK genes more visually, the 20 sequences were selected from the 44 IRK data used for the previous Fig. 3, that is, three Halocynthia roretzi IRKs, four Ciona IRKs, three Caenorhabditis elegans IRKs, and three Caenorhabditis briggsae IRKs. The seven bacterial IRK-like proteins were taken as the outgroup, which was the same as in Fig. 3. The position of KirBAC1.1 was underlined. Alignment, phylogenetic tree building, and Bootstrap for the internal branch test were the same as in Fig. 3. The gaps within nonpreserved regions were carefully deleted manually by the BioEdit program. Then the phylogenetic tree derived from the aligned data was made by the Neighbor Joining Method in the Mega3 v3.1 program, including 269 sites with pairwise deletion of Gap/Missing Data. In Additional file 5, Excel data of intron insertion in various IRK genomes, intron numbers, sizes, and locations for 123 IRK genes used for the analysis of the present study were listed. The identification numbers in GenBank or Ensembl for the genes and their locations in the chromosomes were also included. [see Additional file 5]