Abstract: The cytochrome P450 monooxygenases (P450s, CYPs) constitute a large and complex superfamily of heme-thiolate proteins, which are responsible for the oxidative metabolism of structurally diverse endogenous and exogenous compounds. In this review, recent progress in Bombyx mori P450 diversity, multiple functions, genomic distribution, intron-exon organization and the evolutionary relationships to P450s from Drosophila melanogaster is summarized, and the proposals of B. mori P450 study are also put forward. In the silkworm, the paralog count for P450s is lower than those found in other scavengers and omnivorous phytophagous insects, but substantially higher than that observed in Apis mellifera. The distribution of B. mori P450s in the genome indicates that most of them are tandem arranged on chromosomes. There is a relatively good correlation between intron-exon organization and phylogenetic relationship among these multiple P450s. Comparison of the P450s from B. mori to the P450s from D. melanogaster reveals that there are 10 pairs of recognizable orthologs and the P450s in CYP3 and CYP4 clans are present with species-specific expansion. These diverse P450s have been demonstrated to be associated with growth and development, tolerance to fluoride and resistance to insecticides. The silkworm is a good representative insect of the order Lepidoptera, and it is so expected that it might found theoretical basis and model system for developmental regulation and resistance management of other insects, especially for lepidopteran insects, with the further study of B. mori P450s.

Key words: Silkworm; cytochrome P450 monooxygenase, diversity,  evolutionary relationship, model insect