Qing-Hua Xiao,Wu-Ye Li,Jin Zhang,Jia-Min Yu,Dong-Yang Liu,Jiang-Nan Peng,Mao-Ye Li,Su Liu
In insects, the transcription factor cap ‘n’ collar isoform C (CncC) plays a critical role in the regulation of multiple genes involved in insecticide detoxification. Knockdown of CncC genes leads to increased susceptibility to different types of insecticides in several insect species. However, the CncC gene has not yet been fully characterized in the black cutworm Agrotis ipsilon , a notorious insect pest that causes severe damage to field crops. In this study, the CncC gene (designated AiCncC ) was identified from A. ipsilon . Exposure to a median lethal concentration (LC 50 ) of chlorantraniliprole (CAP) or phoxim (PHO) strongly increased the expression of AiCncC . Silencing of AiCncC by RNA interference significantly increased the susceptibility of A. ipsilon larvae to both insecticides. Moreover, CncC/Maf binding sites were predicted in the putative promoters of two glutathione S -transferase (GST) genes ( AiGSTe1 and AiGSTu1 ) involved in the detoxification of CAP and PHO. The transcription levels of AiGSTe1 and AiGSTu1 were dramatically decreased by silencing AiCncC . These findings indicate that AiCncC is associated with CAP and PHO susceptibility through the regulation of GST genes.
Chao Hu,Ji-Yuan Liu,Wei Wang,David Mota-Sanchez,Shun He,Yu Shi,Xue-Qing Yang
Pest management is mostly accomplished by the use of insecticides. However, the overuse of insecticides has led to the development of resistance. Glutathione S-transferases (GSTs) are vital detoxification enzymes involved in insecticide resistance in insects. In this study, we report the involvement of GSTs in insecticide resistance to lambda-cyhalothrin in Cydia pomonella, a globally quarantined fruit pest. A total of 25 GST, including 22 cytosolic genes and 3 microsomal genes, are identified from the genome database of C. pomonella. These cytosolic genes are further classified into six classes, including four in delta, eight in epsilon, three in omega, three in sigma, one in theta, and one in zeta class, as well as two unclassified genes. The real-time quantitative polymerase chain reaction (RT-qPCR) shows that the majority of these genes are mainly expressed throughout the larval stage and in the midgut of the fourth-instar larvae. Exposure to an LD10 dose of lambda-cyhalothrin resulted in the upregulation of 17 GST genes. Moreover, mRNA levels of most GST genes, with the exception of CpGSTe6, CpGSTd2, CpGSTd4, and CpGSTz1, are considerably higher in a lambda-cyhalothrin-resistant population (ZW_R) than those of susceptible strains. Recombinant CpGSTd1, CpGSTd3, CpGSTe3, and CpGSTs2 can bind and metabolize lambda-cyhalothrin, with the highest metabolic rate observed for CpGSTd3 but no metabolite(s) was detected, supporting the role of GSTs in sequestration of lambda-cyhalothrin. Molecular dynamics simulation analysis indicates that key residues of hydrophobic pocket-derived lipophilic energy S(lipo) interactions with a hydrophobic pharmacophore of lambda-cyhalothrin are crucial for metabolism by CpGSTd3 and further lead to resistance. Our study is the first to experimentally confirm the involvement of GSTs in lambda-cyhalothrin resistance via sequestration and provides new insights into resistance management in C. pomonella.
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