Abstract: 【Aim】 Arginine kinase (AK) is an important phosphogen kinase (regulation factor of energy metabolism) in insects and the only phosphoryl donor that can form effective ATP. It plays the same role as creatine kinase in vertebrates. This study aims to clarify the expression and function of AK gene in lepidopteran pests. 【Methods】 We determined the expression profiles of AK gene in different developmental stages and tissues of the 3rd instar larvae by qRT-PCR, and assayed the AK activity in four lepidopteran pests, Sesamia inferens, Chilo suppressalis, Spodoptera exigua and Spodoptera litura by endpoint method. Furthermore, we analyzed the biological functions of AK genes in these four species by RNAi. 【Results】 qRT-PCR assay revealed that AK gene was expressed at all the developmental stages and in various tissues of the 3rd instar larvae of these four species, indicating that the expression of AK gene has no developmental stage and tissue specificity. The change trend of AK activities in different developmental stages and tissues of the 3rd instar larvae were similar with that of the expression levels of AK gene. At 6 d post injection of dsRNA targeting AK gene, the expression level of AK gene decreased by 30%-50% and the AK activity decreased by about 30% in these four species. At 14 d post injection of dsRNA targeting AK gene, the larval mortality rates of the four species were around 50%, which was significantly higher than those of the control groups. 【Conclusion】 AK gene is constitutively expressed in the four lepidopteran pests. Inhibition of AK gene expression by RNAi can lead to the larval death of these four species. Our results provide a theoretical basis for developing new lepidopteran pest control technologies targeting AK gene.

Key words: Lepidoptera, Sesamia inferens, Chilo suppressalis, Spodoptera exigua, Spodoptera litura, AK gene, spatio-temporal expression profile, enzyme activity, RNAi