RNAi机制可以通过dsRNA诱导同源mRNA的降解，从而导致该基因转录后沉默。RNA干扰作用从发现以来就具有了利用转录后基因沉默（PTGS）来进行抗虫的一种潜在可能性。针对dsRNA的这种作用，研究中提取蚜虫RNA，克隆出蚜虫Cathepsin B基因的干扰片段并构建出RNAi载体，转入本氏烟草中，在转基因烟草体内表达dsRNA。成功构建RNAi载体后，通过农杆菌转化和叶盘法将RNAi载体导入烟草中并采用组织培养方法培养出转基因烟草，通过PCR鉴定显示15株生根的转基因烟草中14株显示阳性。提取转基因烟草的RNA进行RT-PCR和Northern表达分析显示转基因烟草植株中dsRNA表达的存在。实验结果说明了在转基因植物体内表达RNAi载体可以产生dsRNA，从而在蚜虫进食植物时达到利用dsRNA抗蚜虫的作用。

RNAi, the mechanism of which is down regulation of specific gene through dsRNA, has a potential for preventing insect by post-transcriptional gene silencing. The interfering sequence of Aphis gossypii gene Cathepsin B was cloned and the RNAi vector about the interfering sequence was constructed and transferred into tobacco (Nicotiana benthamiana). The RNAi vector was transformed into tobacco via Agrobacterium-mediation using leaf disc method and the regenerated tobacco plants were obtained. Among the 15 strains of transgenic tobacco obtained after tissue culture, 14 lines are positive detected by PCR. And the analysis of RT-PCR and Northern blot of transgenic tobaccos displayed the existence of expression of dsRNA. These results demonstrated that transgenic plants containing RNAi could express dsRNA. For this reason, there was possible that aphid could be resisted when they fed on the transgenic plants.