Silkworm egg proteins at the germ-band formation stage and a functional analysis of BmEP80 protein.

The patterning of embryos in early stages is a critical process for embryo development. In order to understand the molecular mechanism of early embryogenesis in silkworm, 2-DE combined with MALDI-TOF-MS technologies were used to analyze the proteins from diapause-destined eggs at the germ-band formation stage. From over 1000 spots, 93 were selected for analysis and data were obtained from 59 revealing 42 proteins. Gene Ontology annotation showed these proteins were involved in several biological processes at the germ-band formation stage, including cell stress response and protein folding, cell growth and migration, termination of diapause, and nutrition storage. Prominent among them was a new 80 kDa protein, named Bombyx mori egg protein 80 (BmEP80). BmEP80 was a component of the eggshell which was secreted by follicle cells during the late vitellogenesis stage to early choriogenesis stage (FCs -5 to +10). It disappears during early embryogenesis and RNAi against it resulted in the collapse of eggs, thus it is likely that BmEP80 is a new component of the silkworm vitelline membrane.