Effect of Hypoxia on Embryo Development in Silkworm Eggs

Abstract

Abstract Diapause is a common phenomenon during which organisms suspend development to overcome difficult environmental conditions. The silkworm is a classical model for the study of egg diapause. Our previous study showed that gene expression is similar in silkworm eggs treated with hyperoxia or HCl. In the present study, to further explore the mechanism of diapause prevention, nondiapause eggs and hyperoxia-/HCl-activated diapause eggs were treated with hypoxia. Embryo morphology, hatching time, and reactive oxygen species (ROS) levels were analyzed across different developmental stages. The results showed that hypoxia may inhibit the embryonic development of silkworm eggs. The morphology of nondiapause eggs under hypoxia differed from that of nondiapause eggs under normoxia during embryonic development, which, in turn, was similar to that of diapause eggs. Meanwhile, the hatching time of nondiapause eggs under hypoxia was delayed significantly. Moreover, the ROS levels of nondiapause eggs changed under hypoxia, showing a pattern similar to that of diapause eggs. Interestingly, when activated diapause eggs were treated with hypoxia, some eggs hatched in the following spring. These results suggest that early embryogenesis is largely dependent on oxygen levels and that hypoxia may induce a diapause-like state in activated diapause eggs. Additionally, ROS levels may play a key role in diapause. Thus, this study provides valuable information on the mechanisms of diapause and diapause prevention in silkworms.