Abstract
Molting fluid accumulates between the old and new cuticles during periodical ecdysis in Ecdysozoa. Natural defects in insect ecdysis are frequently associated with melanization (an immunity response) occurring primarily in molting fluids, suggesting that molting fluid may impact immunity as well as affect ecdysis. To address this hypothesis, proteomic analysis of molting fluids from Bombyx mori during three different types of ecdysis was performed. Many proteins were newly identified, including immunity-related proteins, in each molting fluid. Molting fluids inhibited the growth of bacteria in vitro. The entomopathogenic fungi Beauveria bassiana, which can escape immune responses in feeding larvae, is quickly recognized by larvae during ecdysis, followed by melanization in molting fluid and old cuticle. Fungal conidia germination was delayed, and no hyphae were detected in the hemocoels of pharate instar insects. Molting fluids protect the delicate pharate instar insects with extremely thin cuticles against microorganisms. To explore the function of molting fluids in ecdysis regulation, based on protein similarity, 32 genes were selected for analysis in ecdysis regulation through RNAi in Tribolium castaneum, a model commonly used to study integument development because RNAi is difficult to achieve in B. mori. We identified 24 molting proteins that affected ecdysis after knockdown, with different physiological functions, including old cuticle protein recycling, molting fluid pressure balance, detoxification, and signal detection and transfer of molting fluids. We report that insects secrete molting fluid for protection and regulation of ecdysis, which indicates a way to develop new pesticides through interrupting insect ecdysis in the future.
Highlights
Periodical ecdysis occurs in insects with molting fluids accumulated among the old and new cuticles
To explore the function of molting fluids in ecdysis regulation, based on protein similarity, 32 genes were selected for analysis in ecdysis regulation through RNAi in Tribolium castaneum, a model commonly used to study integument development because RNAi is difficult to achieve in B. mori
Because RNAi has generally not been successful in the silkworm [8], we used the RNAi sensitive Tribolium as a model to identify molting proteins involved in detoxification, recycling, and signal transduction that affects ecdysis and development following the knockdown of corresponding genes
Summary
Periodical ecdysis occurs in insects with molting fluids accumulated among the old and new cuticles. We observed that the unsuccessful insect ecdysis induced by pathogens is associated with melanization, an innate immunity response, mainly in the molting fluids of the silkworm, Bombyx mori This suggests that molting fluid has functions of immunity protection and ecdysis regulation. Because RNAi has generally not been successful in the silkworm [8], we used the RNAi sensitive Tribolium as a model to identify molting proteins involved in detoxification, recycling, and signal transduction that affects ecdysis and development following the knockdown of corresponding genes. It appears that insects secrete molting fluid for immune protection of pharate instar insect bodies and regulation of ecdysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
