Abstract
Fall armyworm, Spodoptera frugiperda (Smith), has caused significant losses for crop production in China. The fall armyworm is mainly controlled by the chemical insecticides, whereas the frequent application of insecticides would result in the resistance development. Insect cytochrome P450 monooxygenases play an essential part in the detoxification of insecticides. In this study, five P450 genes were selected to determine the role in response to insecticides by RNA interference (RNAi). Developmental expression pattern analysis revealed that S. frugiperda CYP321A8, CYP321A9, and CYP321B1 were highest in second-instar larvae among developmental stages, with 2.04-, 3.39-, and 8.58-fold compared with eggs, whereas CYP337B5 and CYP6AE44 were highest in adult stage, with 16.3- and 10.6-fold in comparison of eggs, respectively. Tissue-specific expression pattern analysis exhibited that CYP321A8, CYP321B1, and CYP6AE44 were highest in the midguts, with 3.56-, 3.33-, and 3.04-fold compared with heads, whereas CYP321A9 and CYP337B5 were highest in wings, with 3.07- and 3.36-fold compared with heads, respectively. RNAi was also conducted to explore detoxification effects of the five P450 genes on chlorantraniliprole. The second-instar larvae became more sensitive to chlorantraniliprole with a higher mortality rate than the control, after silencing CYP321A8, CYP321A9, and CYP321B1, respectively. These findings strongly supported our viewpoint that CYP321A8, CYP321A9, and CYP321B1 may play a critical role in insecticide detoxification. It will provide a basis for further study on regulation of P450 genes and the management of S. frugiperda.
Highlights
Fall armyworm, Spodoptera frugiperda (Smith), is an invasive omnivorous pest throughout the world, mainly harming many crops such as corn, rice, sorghum, and peanut (Goergen et al 2016, Liu et al 2019)
Developmental expression pattern analysis revealed that S. frugiperda CYP321A8, CYP321A9, and CYP321B1 were highest in second-instar larvae among developmental stages, with 2.04, 3.39, and 8.58-fold compared with eggs, whereas CYP337B5 and CYP6AE44 were highest in adult stage, with 16.3- and 10.6-fold in comparison of eggs, respectively
Tissue-specific expression pattern analysis exhibited that CYP321A8, CYP321B1, and CYP6AE44 were highest in the midguts, with 3.56, 3.33, and 3.04-fold compared with heads, whereas CYP321A9 and CYP337B5 were highest in wings, with 3.07- and 3.36-fold compared with heads, respectively
Summary
Spodoptera frugiperda (Smith), is an invasive omnivorous pest throughout the world, mainly harming many crops such as corn, rice, sorghum, and peanut (Goergen et al 2016, Liu et al 2019). Chlorantraniliprole, emamectin benzoate, spinetoram, and Bacillus thuringiensis were used as the main insecticides to control lepidoptera pests (Pan 2005, Cordova et al 2006, Li et al 2019) Some pests such as Plutella xylostella developed serious resistance to chlorantraniliprole (Hu et al 2012, Wang et al 2013, Xia et al.2013), Mythimna separate in the field population developed certain resistance to chlorantraniliprole and emamectin benzoate (Dong et al 2014, Liu et al 2016), and fall armyworm has developed resistance to Bacillus thuringiensis (Monnerat et al 2015). Detoxification metabolism and resistance to insecticides were affected by changing detoxification enzyme activity and related gene expression in pests (Chen et al 2015, Elzaki et al 2015). The inducible expression of some P450 genes by a variety of compounds was a common phenomenon of insect in exposure to various environment, which was called as induction. It is of great significance to study the induction effect of insecticides on fall armyworm for assessing its role in pest control
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