Abstract: 【Aim】 The ABC (ATP-binding cassette) transporters are important transmembrane proteins encoded by a supergene family. The expression of some ABC transporter genes significantly increase in some insecticide resistant strains of insect species. This study aims to clone the full cDNA of ABC transporter genes RhpaABCG9, RhpaABCG20 and RhpaABCG23 of the bird cherry-oat aphid, Rhopalosiphum padi, and to analyze their expression patterns in different developmental stages and different insecticide resistant strains. The results will provide a theoretical knowledge to clarify the biological functions of ABC transporters of R. padi, especially their roles in the resistance to insecticides of this insect. 【Methods】 RT-PCR and RACE were used to clone the full-length cDNAs of three ABC transporter genes from R. padi. The expression levels of the three genes in different developmental stages and different insecticide resistant strains of this aphid were detected by real-time quantitative PCR. 【Results】 The cDNAs of RhpaABCG9, RhpaABCG20 and RhpaABCG23 have an open reading frame (ORF) of 2 103, 2 436 and 2 082 bp with the deduced amino acid sequence of 700, 811 and 693 residues, respectively. Structural analysis showed that all the three proteins have the typical structural features of ABC transporter family. Phylogenetic analysis indicated that the amino acid sequences of these three proteins show high identity to those of the corresponding proteins from Acyrthosiphon pisum. Real-time quantitative PCR analysis showed that the three genes were expressed differently in different developmental stages. The expression level of RhpaABCG20 was not significantly different in various developmental stages. The expression level of RhpaABCG9 was the highest in the 4th instar nymphs and the lowest in the 1st instar nymphs. The expression level of RhpaABCG23 was significantly higher in the 3rd instar nymphs and significantly lower in the 1st instar nymphs than those in other instar nymphs, while there was no significant difference among the other instar nymphs. Compared with that in the susceptible strain, the expression level of RhpaABCG20 in the isoprocarb resistant strain of R. padi was significantly up-regulated, whilst the expression levels of RhpaABCG9 and RhpaABCG23 were insignificantly down-regulated. The expression levels of RhpaABCG20 and RhpaABCG23 in the imidacloprid resistant strain were significantly higher than in the susceptible strain, whilst the expression level of RhpaABCG9 was not significantly up-regulated in the resistant strain. 【Conclusions】 RhpaABCG9, RhpaABCG20 and RhpaABCG23 may play roles in the transport of insecticides in R. padi, and be related to the resistance of this pest to insecticides. The results provide a foundation for further study of the resistance mechanisms, and for the resistance management and integrated pest management of R. padi.

Key words: Rhopalosiphum padi, ABC transporter, gene cloning, expression analysis, insecticide resistance