Disruption of egg‐specific protein causes female sterility in Bombyx mori

Yolk proteins are the main source of nutrients during embryonic and early larval development in oviparous animals. Therefore, vitellogenesis is crucial for reproduction. The silkworm, Bombyx mori, is a model lepidopteran insect in which there are three yolk proteins: vitellin, 30‐kDa protein, and egg‐specific protein (Esp). In this study, we explored the gene function of Esp through transgenic clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR‐associated protein 9 technology‐mediated mutations in the silkworm. We found that Esp mutation resulted in female sterility but had no effect on male fertility. Female mutants could lay eggs after mating, but the eggs were smaller and lighter colored than those laid by wild‐type females. The most important finding is that the eggs laid by female mutants did not hatch. Furthermore, we observed stable inheritance of female sterility caused by Esp mutation through successive generations. Thus, Esp encodes a yolk protein that is crucial for female reproductive success and is a potential target for pest control. Esp plays a key role in female reproduction. Esp deficiency results in female sterility but male fertility. Female sterility caused by Esp mutation can be passed on to offspring stably and the dominant effect could be observed in the mutants. In addition, the competence of the mutants is not affected through the competitive analysis. Our data indicate that Esp is a suitable target gene for genetic sterile insect technology to control lepidopteran pest populations.