Abstract: 【Objective】In this study, we cloned the full-length cDNA of the G protein-coupled receptor kinase 2 (AlGRK2) in Apolygus lucorum, and analyzed its expression profiles. We also clarified the effect of AlGRK2 expression under exogenous ecdysterone hormone 20E in A. lucorum and the role of AlGRK2 in the development of A. lucorum nymphs, laying the foundation for further research on its function in the ecdysone signaling pathway.【Method】We cloned and obtained the AlGRK2 in A. lucorum by RACE method. Using the qRT-PCR method, we determined the relative expression levels of AlGRK2 in different days old (1-16 day) and different tissues (head, thorax, wings, legs, midgut, ovary and fat body) in female adults in A. lucorum. Finally, We analyzed the response of the AlGRK2 in A. lucorum after exogenous 20E induction and RNAi treatment and its effects on the developmental duration of the nymphs, the weight of the 5th instar nymphs and the emergence rate of adults.【Result】The full length of AlGRK2 cDNA is 2 715 bp, and ORF is 2 106 bp. ExPASy predicts that the protein molecular weight is 80.2 kD. Protein structure analysis shows that AlGRK2 contains 4 domains and has the typical domain in the GRK2 protein (PH domain). qRT-PCR results showed that AlGRK2 was expressed in 1-day-old to 16 day-old nymphs of A. lucorum, in which the expression level was the highest at 1th day-old and the lowest at 14-day-old. The AlGRK2 gene was highly expressed in the ovary, midgut, and fat body of female adults and less expressed in the thorax and legs. After exogenous 20E treatment, the expression of AlGRK2 was significantly down-regulated in nymphs at the 1-day-old and the 3-day-old. The relative expression of AlGRK2 in all tissues of females was up-regulated after treating with 20E which compared with control, especially in ovary and fat body. Compared with CK, the developmental duration of nymph, the body weight of the last instar nymph and the emergence rate of adult in A. lucorum were significantly decreased after 20E treatment. In addition, AlGRK2 expression level of A. lucorum significantly decreased in the dsAlGRK2 group compared with the dsGFP group. Compared with the dsGFP group, the mortality rate and the 5th instar developmental period of the dsAlGRK2 group of A. lucorum nymph increased significantly, while the adult emergence rate and the 5th instar nymph body weight decreased significantly.【Conclusion】The expression profile of AlGRK2 in A. lucorum showed the specificity of the developmental stage and the tissue. Exogenous 20E treatment can inhibit the expression of AlGRK2 gene in A. lucorum and delay the growth and development of A. lucorum, and RNAi also shows similar effects. The results provide a theoretical basis for revealing the function of GRK2 and perfecting the ecdysone signal pathway, and laying a foundation for providing new targets for pest control.

Key words: Apolygus lucorum, G protein-coupled receptor kinase 2, gene cloning, relative expression, RNAi