title: Identification of a novel cytochrome P450 CYP321B1 gene from tobacco cutworm (Spodoptera litura) and RNA interference to evaluate its role in commonly used insecticides.
abstract: Insect cytochrome P450 monooxygenases (CYPs or P450s) play an important role in detoxifying insecticides leading to resistance in insect populations. A polyphagous pest, Spodoptera litura, has developed resistance to a wide range of insecticides. In the present study, a novel P450 gene, CYP321B1, was cloned from S. litura. The function of CYP321B1 was assessed using RNA interference (RNAi) and monitoring resistance levels for three commonly used insecticides, including chlorpyrifos, β-cypermethrin and methomyl. The full-length complementary DNA sequence of CYP321B1 is 1814 bp long with an open reading frame of 1 488 bp encoding 495 amino acid residues. Quantitative reverse-transcriptase polymerase chain reaction analyses during larval and pupal development indicated that CYP321B1 expression was highest in the midgut of fifth-instar larvae, followed by fat body and cuticle. The expression of CYP321B1 in the midgut was up-regulated by chlorpyrifos, β-cypermethrin and methomyl with both lethal concentration at 15% (LC15) (50, 100 and 150 μg/mL, respectively) and 50%(LC50) dosages (100, 200 and 300 μg/mL, respectively). Addition of piperonyl butoxide (PBO) significantly increased the toxicity of chlorpyrifos, β-cypermethrin and methomyl to S. litura, suggesting a marked synergism of the three insecticides with PBO and P450-mediated detoxification. RNAi-mediated silencing of CYP321B1 further increased mortality by 25.6% and 38.9% when the fifth-instar larvae were exposed to chlorpyrifos and β-cypermethrin, respectively, at the LC50dose levels. The results demonstrate that CYP321B1 might play an important role in chlorpyrifos and β-cypermethrin detoxification in S. litura.
authors.affiliation: Key Laboratory of Tropical Agro-Environment, Ministry of Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, China.|Guangdong Engineering Research Center for Modern Eco-agriculture and Circular Agriculture, Guangzhou, China.
authors.forename: Rui-Long
authors.initials: RL
authors.lastname: Wang
authors.affiliation: Departments of Entomology, Texas A&M University, Texas, USA.
authors.forename: Keyan
authors.initials: K
authors.lastname: Zhu-Salzman
authors.affiliation: United States Department of Agriculture-Agricultural Research Service, Natural Products Utilization Research Unit, University, Mississippi, USA.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Baerson
authors.affiliation: Key Laboratory of Tropical Agro-Environment, Ministry of Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, China.
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Xin
authors.affiliation: Key Laboratory of Tropical Agro-Environment, Ministry of Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Tropical Agro-Environment, Ministry of Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, China.|Guangdong Engineering Research Center for Modern Eco-agriculture and Circular Agriculture, Guangzhou, China.
authors.forename: Yi-Juan
authors.initials: YJ
authors.lastname: Su
authors.affiliation: Key Laboratory of Tropical Agro-Environment, Ministry of Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, China.|College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.
authors.forename: Ren-Sen
authors.initials: RS
authors.lastname: Zeng
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D008658:Inactivation, Metabolic; D007306:Insecticides / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D034622:RNA Interference; D018411:Spodoptera / Q000235:genetics* / Q000378:metabolism
chemical_list: D007306:Insecticides; D003577:Cytochrome P-450 Enzyme System
keywords: CYP321B1; RNA interference; Spodoptera litura; cytochrome P450 monooxygenases; insecticide resistance