QiufengN is a silkworm strain. During the feeding process of QiufengN, a mutant of black pupal cuticle QiufengNBP was found. Some silkworm pupae of the mutant were unable to easily molt during pupation, and some silkworm eggs produced by developed normally but larvae were unable to break out of the eggshells. These phenomena had not been observed in other black pupa mutants. Genetic analysis showed that the melanization trait of QiufengNBP is controlled by a recessive gene located on the autosome and follows Mendelian inheritance. Results of positional cloning and qRT-PCR showed that the occurrence of black pupae was caused by the mutation of the ebony gene on chromosome 26. 2-DE analysis of the pupal cuticle of QiufengN and QiufengNBP found that the 30K protein, the main storage protein for the growth and development of silkworms and an important energy substance for embryonic development, has changed significantly. In addition, the expression level of Bombyx mori hatching enzyme (BmHEL), which can soften the eggshell during the hatching process of silkworm, was significantly higher in the eggs of black pupae before and after hatching than in normal eggs. The mutation of ebony makes hatching difficult for silkworms, and increases in BmHEL is needed to soften the eggshell. This study showed that ebony may have important effects on the formation of silkworm pigment and egg hatching, and its formation mechanism is complex and deserves further study.
Keywords: 2-DE; 30K protein; BmHEL; Bombyx mori; ebony.
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