Mureed Abbas

BACKGROUND: Chitin is a major component in the extracellular matrix of insects, and its metabolism largely affects insect development and molting. As essential degradative enzymes, chitinases are encoded by multiple genes that differ in size, expression pattern and function in insects. However, our limited knowledge on the functions of different chitinases in Agrotis ipsilon has prevented our application of new technologies to target these genes as new pest management strategies.RESULTS: We revealed 11 full‐length complementary DNA sequences of chitinase genes (AiChts) from A. ipsilon transcriptome. Although the domain architecture of these chitinases varied greatly, they all contained at least one chitinase catalytic domain. Developmental stage‐ and tissue‐dependent expression profiles showed that most AiChts had the highest expression in the pupal stage. Furthermore, AiCht2, AiCht6, AiCht7 and AiCht10 were mainly expressed in the integument, whereas AiCht8 and AiCht‐h had the highest expression in the midgut. The RNA interference (RNAi) experiment revealed that knockdown of AiCht10 or the imaginal disc growth factor gene (AiIDGF) induced high larval mortality. Larvae failed to shed the old cuticle during molting after the injection of double‐stranded RNA targeting AiCht10 (dsAiCht10), whereas the larval bodies shrunk and blackened after the injection of dsRNA targeting AiIDGF (dsAiIDGF).CONCLUSION: Our results revealed for the first time the important functions of AiCht10 and AiIDGF in A. ipsilon. These genes are essential for larval development, and can potentially serve as new targets for RNAi‐based pest management. © 2022 Society of Chemical Industry.

RNA interference (RNAi) is a sequence-specific gene silencing mechanism that holds great promise for effective management of agricultural pests. Previous studies have shown that the efficacy of RNAi varies among different insect species, which limits its wide spread application in the field of crop protection. In this study, we identified and characterized six core RNAi pathway genes including OfDicer1, OfDicer2, OfR2D2, OfAgo1, OfAgo2, and OfAgo3 from the transcriptomic database of the Asian corn borer (Ostrinia furnacalis). Domain analysis showed that the six deduced proteins contained the necessary functional domains. Insect developmental stage- and tissue-specific expression analysis showed that five genes were expressed in all the stages and tissues examined except OfAgo3, which showed low expression in larvae, and high expression in pupae and adults and in the midgut. RT-qPCR was performed to examine the response of these six genes to exogenous double-stranded RNA (dsRNA). Interestingly, the transcript levels of OfDicer2 and OfAgo2 were significantly enhanced after the injection of dsEGFP at different time points and tissues investigated. Consequently, the RNAi efficiency in targeting the insect endogenous genes can be greatly enhanced in the hemolymph or midgut. Taken together, our investigations suggest that RNAi efficiency can be enhanced by pre-injection of dsRNA to induce the RNAi core machinery genes, which could be a useful strategy to improving RNAi efficiency for studying gene functions under laboratory conditions.