Abstract: 【Aim】 To reveal the relationship between the feeding of Bt proteins by Spodoptera frugiperda larvae and the changes in the expression levels of related ABC (ATP-binding cassette transporter) genes in the midgut. 【Methods】 Artificial diets containing Cry1Ab (LC₇₀=240.2 μg/g) or Cry1Fa (LC₇₀=270.0 μg/g) activated crystal protein were used to feed the 4th instar larvae of S. frugiperda for 48 h, respectively. Transcriptome sequencing of midgut and bioinformatics analysis were used to screen differentially expressed genes in the midgut after treatment. RT-qPCR was used to verify the expression levels of the differentially expressed ABC genes. 【Results】 A total of 1 305 and 1 202 differentially expressed genes were detected in the midgut transcriptome of the 4th instar larvae of S. frugiperda fed with the artificial diet containing 240.2 μg/g Cry1Ab and 270.0 μg/g Cry1Fa, respectively, compared with those fed with the normal artificial diet (the control group). There were 994 and 912 differentially expressed genes between the Cry1Ab and Cry1Fa treatment groups and the control group, respectively, and were annotated by GO function into three categories biological process, molecular function and cell component. Among the nine differentially expressed ABC family genes screened, there were four differentially expressed ABC genes (three up-regulated and one down-regulated) between the Cry1Ab treatment group and the control group and five differentially expressed ABC genes (two up-regulated and three down-regulated) between the Cry1Fa treatment group 
and the control group. The expression levels of two ABC genes (LOC118267200 and LOC118267201) in the Cry1Ab and Cry1Fa treatment groups were significantly up-regulated as compared to those in the control grpup. RT-qPCR validation results showed that the expression levels of three and two ABC genes in the Cry1Ab treatment group were extremely significantly up-regulated and down-regulated, respectively, and those of five ABC genes and one ABC gene in the Cry1Fa treatment group were up-regulated and down-regulated, respectively, as compared to those in the control grpup. 【Conclusion】 The intake of Cry1Ab and Cry1Fa proteins could affect the expression levels of certain ABC family genes in the midgut of S. frugiperda larvae, and the expression level changes of these genes are related to pest resistance. After comparison, we found that the expression levels of ABCC family and ABCG8 genes changed significantly. This study provides a theoretical basis for further clarifying the role of ABC transporter proteins in the insecticidal mechanism of Bt proteins in S. frugiperda and the rational use of Bt proteins for controlling S. frugiperda and delaying resistance.

Key words: Spodoptera frugiperda, Bt protein, ABC transporter protein, transcriptome sequencing, Cry1Ab, Cry1Fa