Figure 4: Phylogenetic relationships of the BTB protein genes of the silkworm with those of other surveyed insects. Based on the amino acid sequences of the BTB domains, a neighbor-joining phylogenetic tree of all insect BTB protein genes was constructed using the ClustalX program and visualized using the MEGA4 software. The grouping clade for the orthologs of a silkworm BTB protein gene that showed a 1 : 1 : 1 : 1 : 1 orthologous relationship among all five surveyed insect species is indicated by a red cambered line. The names of all BTB protein genes from a single insect species are indicated in the same color.