Abstract: Acetylcholinesterase（AChE）is a target of organophosphorus- and carbamate-type pesticides. This study focuses on the acetylcholinesterase genes of Helicoverpa armigera,including the effects of phoxim,methomyl and feeding the ace dsRNA-expressing bacteria on the transcriptional activities of acetylcholinesterase genes,which may provide reference for the chemical control and RNAi-based control of H. armigera. The real-time quantitative PCR method was used to analyze the transcriptional levels of ace genes in phoxim- and methomyl-induced 4th instar larvae of H. armigera for 12 h,24 h,36 h,48 h,and 60 h. The 2th instar H. armigera larvae were fed with dsRNA-expressing bacteria,and the silencing effect of ace genes after RNAi was detected. Our results showed that the transcriptional levels of ace1 and ace2 were down-regulated at 12 h after phoxim and methomyl induction;subsequently,the transcriptional level of ace1 was down-regulated while the transcriptional level of ace2 was up-regulated. The transcriptional levels of ace1 and ace2 were down-regulated obviously at 24 h and 48 h then increased slightly after RNAi treatment. It is inferred that the pesticide treatment leads to the physiological and metabolic damages of H. armigera and consequently the significant reduction of transcriptional levels of ace1 and ace2;subsequently,the ace2 expression was decreasing constantly while the ace1 expression was gradually increasing,which might be related to compensation for pesticides' inhibition to AchE enzyme activity. RNAi treatment caused varied inhibitions to both growth and development of H. armigera,as well as the obvious inhibitions to the transcriptions of ace1 and ace2 genes. The above results provide a reference for the control of H. armigera while using acetylcholinesterase and its coding genes as the target.

Key words: Helicoverpa armigera larvae, phoxim, methomyl, acetylcholinesterase genes, RNAi