Physiological Characterization of the Chitin Synthase A Gene Responsible for Biosynthesis of Cuticle Chitin in Culex Pipiens Pallens (Diptera: Culicidae)

Abstract

Background: The pathogens transmitted by mosquitoes (Culex pipiens pallens) to humans and animals cause several emerging and resurgent infectious diseases. Increasing insecticide resistance requires rational action to control the target vector population. Chitin is indispensable for insect growth and development and absent from vertebrates and higher plants. Chitin synthase A (CHSA) represents a crucial enzyme in chitin synthesis; therefore, identifying and characterizing how CHSA determines the chitin content might help with novel vector control strategies. Results: The injection of small interfering RNA targeting CHSA (siCHSA) to knock down CHSA transcripts of in larval, pupal, and adult stages, showed different lethal phenotypes. In the larval and pupal stages, CHSA knockdown prevented larval molting, pupation, and adult eclosion, and affected the production of chitin and chitin degradation, which resulted in an ecdysis defect phenotype of mosquitoes. In the adult stage, it also affected the laminar organization of mesoderm and the formation of pseudo orthogonally large fibers of the endoderm. Conclusion: The present study provides a systematic and comprehensive description of the effects of CHSA on morphogenesis and metamorphosis. The results showed that CHSA not only affects chitin synthesis during molting, but also might be involved in chitin degradation. Our result further showed that CHSA is important for the structural integrity of the adult mosquito cuticle.

Impact of agrochemical pollutant mixtures on the selection of insecticide resistance in the malaria vector Anopheles gambiae. Insights from experimental evolution and transcriptomics

“…This gene cluster also shows a clear selection signature upon insecticide mixture selection. A cuticular component of xenobiotic resistance is further supported by the over-transcription of chitin synthase, an enzyme playing a key role in cuticle formation (101). Deciphering whether the over-transcription of these multiple cuticle proteins is associated with physiological cuticle alteration (cuticle thickening and/or altered insecticide penetration) in selected lines deserves further work.…”