The Role Of ABCB1 In The Resistance Mechanism Of Spodoptera Frugiperda

Spodoptera frugiperda is an agricultural pest of Lepidoptera Noctuidae.It is native to tropical and subtropical America.At present,the situation of prevention and control in China is very serious.Since its invasion into China in 2019,Spodoptera frugiperda has seriously damaged the production of corn,rice and other crops and posed a major threat to food security in many areas.Due to the characteristics of high efficiency,low cost,and easy mechanization of chemical pesticides,the current control of this pest mainly relies on chemical pesticides.However,although pesticides have been proven to be effective,the long-term use of chemical drugs will not only cause irreversible pollution to the environment,but also lead to resistance in field populations,making pest control more difficult.Therefore,the problem of drug resistance in the field population also needs to be paid great attention.ATP-binding cassette transporter 1（ABCB1,or P-glycoprotein/P-gp）plays an important role in multiple drug resistance mechanisms in mammals,and it has also been shown to be involved in the metabolism of several lepidopteran insects certain insecticides,but the exact function of this transporter in Spodoptera frugiperda is unclear.In this paper,CRISPR/Cas9-mediated gene editing technology was used to knock out the ABCB1 gene in the field population of Spodoptera frugiperda.And a homozygous strain of ABCB1-knockout strain was obtained through screening.In this way,the potential mechanism of action in the sensitivity of the ABCB1 transporter of Spodoptera frugiperda to chemical pesticides or Bacillus thuringiensis protein（Bt protein）was explored.We compared the mortality of S.frugiperda wild strain（DH19）and ABCB1 knockout strain（ABCB1-KO）after treatment with 10 insecticides and 3 Bt proteins.Bioassay results showed that compared with the wild strain DH19,the gene knockout strain ABCB1-KO was significantly more sensitive to emamectin benzoate,beta-cypermethrin and chlorantraniliprole.The LC₅₀of emamectin benzoate to knockout strain ABCB1-KO was 0.0475 ng/cm²,while the LC₅₀of emamectin benzoate to wild strain DH19 was 0.1986 ng/cm²,which was 4.18 times that of ABCB1-KO.The LC₅₀of the knockout strain ABCB1-KO was 5.3417 ng/cm²,while the LC₅₀of the wild strain DH19 was 15.6798 ng/cm²,which was 2.94 times of that of ABCB1-KO.Compared with the LC₅₀（437.2371 ng/cm²）of ABCB1-KO,the LC₅₀of wild strain DH19 was1263.8372 ng/cm²,which was 2.89 times of that of ABCB1-KO.Besides,there was no significant difference in the sensitivity of wild strain and knockout strain to seven other pesticides:indoxacarb,tebufenozide,bifenthrin,chlorpyrifos,abamectin,chlorfenapyr,decamethrin and three Bt toxin:Cry1Ab,Cry1Fa and Vip3Aa.The results of this study demonstrated that ABCB1 plays an important role in the susceptibility of Spodoptera frugiperda to emamectin benzoate,beta-cypermethrin and chlorantraniliprole,and knockout of the ABCB1 gene can increases susceptibility to emamectin benzoate,beta-cypermethrin and chlorantraniliprole significantlv in Spodoptera Frugiperda,which also revealed that overexpression of ABCB1 may causes resistance of Spodoptera frugiperda to emamectin benzoate,beta-cypermethrin and chlorantraniliprole.In addition,the gene editing strain of Spodoptera frugiperda（ABCB1-KO）and the wild strain of Spodoptera frugiperda（DH19）treated with beta-cypermethrin and chlorantraniliprole were sent to test the transcriptome.This conclusion was verified by analyzing the correlation of samples and differentially expressed genes.This study provides further evidence for the participation of ABCB1 gene in insecticide resistance,and also verified the feasibility of CRISPR/Cas9 gene editing technology in the gene fragment of Spodoptera frugiperda.