Development of an Injection Method for the Genetic Engineering of Diapause Silkworm Egg Using Dimethyl Sulfoxide

Genetic engineering of the domesticated silkworm Bombyx mori is a useful tool for developing sericulture. New races that produce recombinant silk with fluorescent color and spider silk protein have been constructed. Strains resistant to B. mori nuclear polyhedrosis virus have also been constructed and started to rear in the field. In this genetic engineering method, the use of nondiapause eggs that do not arrest embryonic development is indispensable as it includes the injection process of vector DNA into the eggs. However, most silkworm strains are bivoltine or univoltine and lay diapause eggs that arrest their embryonic development. Thus, applying this method to these silkworm strains is impossible. To enable the application, whether dimethyl sulfoxide (DMSO), which can prevent the diapause of eggs, can be used to develop an injection method for the genetic engineering of diapause strains was investigated. The DMSO treatment worked well for this purpose, and an injection method for the genetic engineering of diapause eggs was successfully developed. This method gave high hatchability in the injection of diapause eggs. Genetically modified silkworms were efficiently created in three different diapause silkworms: hybrid race and Japanese and Chinese strains. Thus, DMSO treatment is useful for creating genetically modified silkworms.