The Exact Timing of Microinjection of Parthenogenetic Silkworm Embryos Is Crucial for Their Successful Transgenesis

Abolition of egg diapause by ablation of suboesophageal ganglion in parental females is compatible with genetic engineering methods

Microinjection of genetic material into non-diapause eggs is required for genetic engineering of silkworms. Besides diapause could be useful for maintaining transgenic lines, a drawback of this technology is that most standard silkworm strains and experimental lines of interest produce diapausing eggs. Several approaches have been developed to abolish diapause but none are very efficient. Here, we investigated the ablation of the suboesophageal ganglion (SG) in female pupae, which is a source of the hormone required to trigger egg diapause, as a mean to abolish diapause. We showed that SG-ablation is a reliable method to produce nondiapause eggs. Additionally, the challenge associated with lower fecundity of females with SG ablation was resolved by injecting pilocarpine into the mated female. We also investigated the suitability of nondiapause eggs laid by SG-ablated females for transgenesis, targeted mutagenesis, and induction of parthenogenetic development. Our results demonstrated SG-ablation to be a useful and simple method for expanding the possibilities associated with genetic engineering in silkworms.