In silico Identification of Novel Chitinase-Like Proteins in the Silkworm, Bombyx mori, Genome

In insects, chitinases participate in the periodic shedding of old exoskeletons and the turnover of peritrophic membranes. Chitinase family members have been identified in dozens of species, including Tribolium castaneum, Drosophila melanogaster, and Anopheles gambiae. In this study, nine chitinases and three hypothetical chitinases have been identified in Bombyx mori L. (Lepidoptera: Bombycidae) through genome-wide searching. Phylogenetic analyses revealed that seven of them belong to the seven chitinase groups, respectively. BmCht25 and BmCht26 could not be grouped into the known chitinase groups, and might belong to two new groups of the chitinase family. BmCht10, BmCht25, and BmIDGF have glutamate amino acid substitutions in the active catalytic domain. Only BmCht5 and BmCht10 contain CBD domain and PEST sequences (rich in proline, glutamic acid, serine, and threonine). BmCht5 and BmCht26 are located on chromosome 7, and others (BmCht6, BmCht7, BmCht10, BmCht11, BmCht20, BmIDGF) are located on separate chromosomes of Bombyx mori, respectively. The present study provides important background information for future studies using Bombyx mori as a model organism for insect development and virus and host interaction.