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ARS Home » Southeast Area » Stoneville, Mississippi » Southern Insect Management Research » Research » Publications at this Location » Publication #341063
Research Project: Integrated Insect Pest and Resistance Management on Corn, Cotton, Sorghum, Soybean, and Sweet Potato

Location: Southern Insect Management Research

Title: Cytochrome P450 genes from the aquatic midge Chironomus tentans: Atrazine-induced up-regulation of CtCYP6EX3 contributing to oxidative activation of chlorpyrifos

Author
item TANG, GUANGHUI - Northwest Agriculture And Forestry University
item YAO, JIANXIU - Kansas State University
item LI, DAQI - Kansas State University
item HE, YANPING - Kansas State University
item Zhu, Yu Cheng
item ZHANG, XIN - Kansas State University
item ZHU, KUN YAN - Kansas State University

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2017
Publication Date: 7/27/2017
Publication URL: http://handle.nal.usda.gov/10113/5801798
Citation: Tang, G., Yao, J., Li, D., He, Y., Zhu, Y., Zhang, X., Zhu, K. 2017. Cytochrome P450 genes from the aquatic midge Chironomus tentans: Atrazine-induced up-regulation of CtCYP6EX3 contributing to oxidative activation of chlorpyrifos. Chemosphere. 186: 68-77. https://doi.org/10.1016/j.chemosphere.2017.07.137.
DOI: https://doi.org/10.1016/j.chemosphere.2017.07.137

Interpretive Summary: The full lengths of 19 cytochrome P450 monooxygenase (CYP) genes were sequenced from an aquatic midge, a commonly used freshwater invertebrate model. Functional analysis of CtCYP6EX3 gene confirmed its atrazine (herbicide)-induced oxidative activation for chlorpyrifos (organophosphate insecticide) by using a nanoparticle-based RNA interference (RNAi) approach. Phylogenetic analysis of the 19 CYPs along with a previously reported CYP (CtCYP4G33) revealed that they belong to three different clans, including 3 in CYP4, 15 in CYP3, and 2 in mitochondrial CYP group. When third-instar larvae were exposed to atrazine at 5000 µg/L, the transcription of CtCYP6EX3, CtCYP6EV3, CYP9AT1 and CtCYPEX1 was significantly up-regulated. To examine whether CtCYP6EX3 played a role in oxidative activation of chlorpyrifos to chlorpyrifos-oxon, we evaluated larval susceptibility to chlorpyrifos after the expression of CtCYP6EX3 was suppressed by RNAi. The larvae fed chitosan/dsCtCYP6EX3 nanoparticles showed a significantly decreased CtCYP6EX3 transcript (53.1%) as compared with the control larvae fed chitosan/dsGFP nanoparticles. When the CtCYP6EX3-silenced larvae were exposed to chlorpyrifos at 6 µg/L or its binary mixture with atrazine (chlorpyrifos at 3µg/L and atrazine at 1000 µg/L), the larvae became less susceptible to the pesticides as their mortalities decreased by 24.1% and 20.5%, respectively. These results along with our previous findings demonstrated that the increased toxicity of chlorpyrifos was due to an enhanced oxidative process from chlorpyrifos to chlorpyrifos-oxon by CtCYP6EX3 as RNAi of the gene led to decreased susceptibility of C. tentans larvae to chlorpyrifos alone and the binary mixture of atrazine and chlorpyrifos.

Technical Abstract: The open reading frames of 19 cytochrome P450 monooxygenase (CYP) genes were sequenced from Chironomus tentans, a commonly used freshwater invertebrate model. Functional analysis of CtCYP6EX3 confirmed its atrazine-induced oxidative activation for chlorpyrifos by using a nanoparticle-based RNA interference (RNAi) approach. Phylogenetic analysis of the 19 CYPs along with a previously reported CYP (CtCYP4G33) revealed that they belong to three different clans, including 3 in CYP4, 15 in CYP3, and 2 in mitochondrial CYP group. When third-instar larvae were exposed to atrazine at 5000 µg/L, the transcription of CtCYP6EX3, CtCYP6EV3, CYP9AT1 and CtCYPEX1 was significantly up-regulated. To examine whether CtCYP6EX3 played a role in oxidative activation of chlorpyrifos to chlorpyrifos-oxon, we evaluated larval susceptibility to chlorpyrifos after the expression of CtCYP6EX3 was suppressed by RNAi. The larvae fed chitosan/dsCtCYP6EX3 nanoparticles showed a significantly decreased CtCYP6EX3 transcript (53.1%) as compared with the control larvae fed chitosan/dsGFP nanoparticles. When the CtCYP6EX3-silenced larvae were exposed to chlorpyrifos at 6 µg/L or its binary mixture with atrazine (chlorpyrifos at 3µg/L and atrazine at 1000 µg/L), the larvae became less susceptible to the pesticides as their mortalities decreased by 24.1% and 20.5%, respectively. These results along with our previous findings demonstrated that the increased toxicity of chlorpyrifos was due to an enhanced oxidative process from chlorpyrifos to chlorpyrifos-oxon by CtCYP6EX3 as RNAi of the gene led to decreased susceptibility of C. tentans larvae to chlorpyrifos alone and the binary mixture of atrazine and chlorpyrifos.