larval integument of silkworm LC-MSMS

The Dominant obese translucent (Obs) mutant of the silkworm results in a short and stout larval body, translucent phenotype, and abnormal pigmentation in the integument. The Obs mutant also displays difficulties in ecdysis and metamorphosis. In the present study, to gain an understanding of multiple Obs phenotypes, we investigated the phenotypes of Obs and performed a comparative analysis of the larval integument proteomes of Obs and normal silkworms. The phenotypic analysis revealed that the Obs larvae are indeed short and fat, and that chitin and uric acid content were lower but melanin content was higher in the Obs mutant. Proteomic analysis revealed that 244 proteins were significantly differentially expressed between Obs and normal silkworms, some of which are involved in uric acid metabolism and melanin pigmentation. Twenty-six proteins were annotated as cuticular proteins, including RR motif-rich cuticular proteins (CPR), glycine-rich cuticular protein (CPG), hypothetical cuticular protein (CPH), cuticular protein analogous to peritrophins (CPAP), and the chitin_bind_3 motif proteins, and accounted for over 84% of the abundance of the total significantly differentially-expressed proteins identified. Moreover, 22 of the 26 cuticular proteins were down-regulated in the Obs mutant. Comparative proteomic analysis suggested that the multiple phenotypes of the Obs mutant are related to changes in the expression of proteins that participate in cuticular formation, uric acid metabolism, and melanin pigmentation. These results also provide a reference for studying the gene responsible for the Obs mutant.