Abstract: RNA interference (RNAi) is the process of sequence-specific post-transcriptional gene silencing initiated by double-stranded RNA (dsRNA) which is homologous in sequence to the silenced gene. The cadherin-like protein, similar to cadherin, lies in brush border membrane vesicles (BBMV) of insect. It had been confirmed to be a receptor of Bacillus thuringiensis (Bt) insecticidal protein in several insects. In this study, two cDNA segments (CAD1 and CAD2) encoding the cadherin-like protein gene were cloned through RT-PCR technique using gene specific primers; double-stranded RNA (dsRNA) was synthesized by using the two gene segments respectively, and microinjected into 3rd instar larvae of Plutella xylostella; and the effects of different target sites, dose and silencing time on cadherin mRNA expression level were assayed. The results showed that the expression of cadherin-like gene was reduced sharply at 48 h after the dsRNA corresponding to CAD1 segment was injected and restored at 72 h. The immunoblotting results indicated that cadherin-like protein in BBMV of P. xylostella was reduced markedly at 48 h after injection. The cadherin-like gene was silenced successfully in this experiment, and the establishment of RNAi technique can help reveal the gene function of P. xylostella including cadherin-like gene.

Key words: Plutella xylostella, Bt, cadherin-like protein, RNAi, gene silencing