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Simple Summary: The CRISPR/Cas9 gene editing and biochemical analysis show that knocking out the Sf-FGFR or Sf-SR-C gene will not change the sensitivity of Spodoptera frugiperda to Vip3Aa. Vip3Aa is a novel insecticidal protein secreted by Bacillus thuringiensis (Bt) during its vegetative growth stages. It has high insecticidal activity against lepidopteran pests such as Spodoptera frugiperda, and has no cross-resistance with Cry insecticidal proteins. As a new type of insecticide, it plays an important role in controlling agricultural pests. However, the insecticidal mechanism of the Vip3Aa toxin, especially its definite receptors, have not been fully revealed. In this study, the previously reported Vip3Aa receptor genes Sf-FGFR and Sf-SR-C were knocked out separately using the CRISPR/Cas9 system. Bioassay results showed that the sensitivity of these two knockout strains to Vip3Aa were not significantly changed compared to that of the normal strain. The current results are not consistent with the previously reports that Sf-SR-C and Sf-FGFR were the receptors of Vip3Aa in vitro. This suggests that the Sf-SR-C and Sf-FGFR genes we tested may not be critical in the mode of action of Vip3Aa in vivo in Spodoptera frugiperda. [ABSTRACT FROM AUTHOR]

Simple Summary: Spodoptera frugiperda is an invasive lepidopteran pest that causes extensive damage to many commercial crops. To control this pest, the use of chemical pesticides has become increasingly important because of their high efficiency, low cost and ease of mechanized operations. However, despite the proven effectiveness of pesticides, the long-term use of chemicals not only pollutes the environment, but also leads to resistance in field populations, making pest control more difficult. In this study, we used the CRISPR/Cas9 system to generate an ABCB1 knockout strain to explore its potential role in determining susceptibility to chemical pesticides or Bt toxins. We compared the mortality of WT strains and knockout strains treated with 10 insecticides and three Bt proteins, and found that the insects were significantly more susceptible to the three insecticides (emamectin benzoate, beta-cypermethrin and chlorantraniliprole) after ABCB1 was knocked out. Our results showed that ABCB1 is closely related to the detoxification metabolism of some pesticides, and suggest that the resistance of Spodoptera frugiperda to emamectin benzoate, beta-cypermethrin and chlorantraniliprole may be related to the overexpression of ABCB1. This lays a foundation for a follow-up study on the resistance mechanism of Spodoptera frugiperda. ATP-binding cassette transporter B1 (ABCB1, or P-glycoprotein) is known to be an important participant in multidrug resistance in mammals, and it also has been proved as a transporter for some insecticides in several lepidopteran insects, yet the precise function of this transporter in Spodoptera frugiperda is unknown. Here, we generated a SfABCB1 knockout strain of the S. frugiperda using the CRISPR/Cas9 system to explore its potential roles in determining susceptibility to chemical insecticides or Bt toxins. Bioassay results showed that the susceptibility of SfABCB1 knockout strain to beta-cypermethrin, chlorantraniliprole and emamectin benzoate were significantly increased compared with the wild-type strain DH19, whereas there were no changes to Bt toxins for Cry1Ab, Cry1Fa and Vip3Aa. Our results revealed that SfABCB1 plays important roles in the susceptibility of S. frugiperda to beta-cypermethrin, chlorantraniliprole and emamectin benzoate, and imply that overexpression of ABCB1 may contribute to beta-cypermethrin, chlorantraniliprole and emamectin benzoate resistance in S. frugiperda. [ABSTRACT FROM AUTHOR]