Chitin synthases are required for survival, fecundity and egg hatch in the red flour beetle, Tribolium castaneum

The synthesis of chitin, the beta-1,4-linked polymer of N-acetylglucosamine, is catalyzed by chitin (CHS). Chitin is essential for the structural integrity of the exoskeletal cuticle and midgut membrane (PM) of insects. To study the functions of the two chitin synthase genes, TcCHS-A and during embryonic and adult development in the red flour beetle, Tribolium castaneum, RNA (RNAi) experiments were carried out. When dsRNA for TcCHS-A was injected into male or female adults, all insects died 5-7 d after the adult molt, and the females failed to oviposit prior to death. dsTcCHS-A was injected into young adults 1-2 d post-eclosion, a similar lethal phenotype was after 5 d and no oviposition occurred. When dsTcCHS-A injections were delayed until after maturation (7-10 d post-eclosion), the treated females did oviposit and the resulting embryos to develop normally. However, the chitin content of the eggs was dramatically reduced, the became twisted and enlarged, and the eggs did not hatch. Adults treated with dsRNA for exhibited little or no chitin in their PM and died about 2 wk after injection. None of the females oviposited, which was probably a secondary effect caused by starvation. These results extend previous findings that CHS genes are required for all types of molt. The present study also that these genes have additional roles in embryonic and adult development. (c) 2008 Elsevier Ltd. All rights