Abstract
Insect pests cause serious crop damage and develop high-level resistance to chemical insecticides and Bacillus thuringiensis (Bt) insecticidal Cry toxins. A new promising approach for controlling them and overcoming this resistance is RNA interference (RNAi). The RNAi-based insect control strategy depends on the selection of suitable target genes. In this study, we cloned and characterized a novel ABC transporter gene PxABCH1 in diamondback moth, Plutella xylostella (L.). Phylogenetic analysis showed that PxABCH1 is closely related to ABCA and ABCG subfamily members. Spatial-temporal expression detection revealed that PxABCH1 was expressed in all tissues and developmental stages, and highest expressed in head and male adult. Midgut sequence variation and expression analyses of PxABCH1 in all the susceptible and Bt-resistant P. xylostella strains and the functional analysis by sublethal RNAi demonstrated that Cry1Ac resistance was independent of this gene. Silencing of PxABCH1 by a relatively high dose of dsRNA dramatically reduced its expression and resulted in larval and pupal lethal phenotypes in both susceptible and Cry1Ac-resistant P. xylostella strains. To our knowledge, this study provides the first insight into ABCH1 in lepidopterans and reveals it as an excellent target for RNAi-based insect pest control and resistance management.
Highlights
To be US $ 4–5 billion annually[12]
Given that the role of ATP-binding cassette (ABC) transporters in chemical insecticide and Bt bioinsecticide resistance is well documented in the literature[36,37] and elevated levels of ABCH transcripts have been reported in two insecticide-resistant arthropods including P. xylostella[26] and T. urticae[37], it is deserves to be seen whether ABCH transporters are associated with insecticide resistance in insects and it deserves to be determined whether ABCH transporters can be used as potential targets for RNA interference (RNAi)-based control of these insecticide-resistant insects
We cloned and characterized this novel ABCH subfamily gene (PxABCH1, orthologous gene of CG9990) in P. xylostella, our overall experimental results demonstrated that PxABCH1 gene is independent of Cry1Ac resistance in P. xylostella, our in vivo RNAi results revealed that remarkably suppression of PxABCH1 expression by injection or oral delivery of a relatively high dose of dsRNA was lethal to larvae and pupae in both susceptible and Cry1Ac-resistant P. xylostella strains, and the caused larval desiccation phenotype indicated that the PxABCH1 might act as transporters of cuticular lipids like its ortholog TcABCH-9C in T. castaneum
Summary
To be US $ 4–5 billion annually[12]. Until now, the application of chemical insecticides still remains the major strategy for controlling P. xylostella because these chemicals are easy to apply and have been effective. An excellent study utilized RNAi to demonstrate that knockdown of the TcABCH-9C (orthologous gene of CG9990) can result in the larval desiccation phenotype and negative effects on adult egg-laying and egg-development that is similar to knockdown of TcABCG-4C in Tribolium castaneum, suggesting that TcABCH-9C might act as transporters of cuticular lipids just like TcABCG-4C in T. castaneum[34] Since that these ABCH transporters only exist in invertebrate (except some teleosts like zebrafish) and silencing of their expression can induce lethal phenotype in insects, they might be used as suitable targets for RNAi-based insect pest control[35,36]. The results demonstrated that the ABCH1 can serve as a valuable target for the novel RNAi-based insect pest control and resistance management strategy
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