We report a draft sequence for the genome of the domesticated silkworm (Bombyx mori), covering 90.9% of all known silkworm genes. Our estimated gene count is 18,510, which exceeds the 13,379 genes reported for Drosophila melanogaster. Comparative analyses to fruitfly, mosquito, spider, and butterfly reveal both similarities and differences in gene content.

Background: Glucosidation plays a major role in the inactivation and excretion of a great variety of both endogenous and exogenous compounds. A class of UDP-glycosyltransferases (UGTs) is involved in this process. Insect UGTs play important roles in several processes, including detoxication of substrates such as plant allelochemicals, cuticle formation, pigmentation, and olfaction. Identification and characterization of Bombyx mori UGT genes could provide valuable basic information for this important family and explain the detoxication mechanism and other processes in insects.

Pseudoxanthoma elasticum (PXE) is caused by mutations in the ABCC6 gene, which encodes a putative efflux pump, ABCC6. The zebrafish (Danio rerio) has two ABCC6-related sequences. To study the function of abcc6 during zebrafish development, the mRNA expression levels were measured using RT-PCR and in situ hybridization. The abcc6a showed a relatively high level of expression at 5 days post-fertilization (dpf) and the expression was specific to the Kupffer’s vesicles. The abcc6b expression was evident at 6 hpf and remained high up to 8 dpf, corresponding to embryonic kidney proximal tubules. Morpholinos were designed to both genes to block translation and to prevent pre-mRNA splicing. Injection of the abcc6a morpholinos into 1–4 cell zebrafish embryos decreased gene expression by 54 to 81%, and induced a phenotype, cardiac edema and curled tail associated with death at around 8 dpf. Microinjecting zebrafish embryos with full-length mouse Abcc6 mRNA together with the morpholino completely rescued this phenotype. No phenotypic changes were observed when the abcc6b gene morpholino was injected to embryos, with knock-down efficiency of 100%. These results suggest that abcc6a is an essential gene for normal zebrafish development and provide novel insight into the function of ABCC6, the gene mutated in PXE.

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