With the development of dna recombination technology , there are also some reports about the expression of recombined ifn protein by prokaryotic expression system , but the expressed proteins often consist in the form of inclusion body = the operations about extracting and purifying proteins are very complicated , biological activity of proteins are not high 随着dna重组技术的发展，国内外亦有利用原核表达系统表达重组ifn蛋白的报道，但表达的目的蛋白常以包涵体形式存在，提取纯化操作步骤复杂、蛋白活性不高。
The results were as following : 1 . construction and identifcation of recombinant plant expression vector pbi ! 2i - th by dna recombination technology , sweet protein thaumatin gene was cloned into plant expression vector pbii2i . recombinant plasmid pbii2i - th was constructed successfully by enzyme cutting and electrophoresis 甜蛋白thaumatin基因植物表达质粒pbi _ ( 121 ) - th的构建与鉴定利用dna重组技术，将植物甜蛋白thaumatin基因克隆至植物表达载体pbi _ ( 121 )中，通过酶切、电泳，鉴定thaumatin基因已成功构建到植物表达质粒pbi _ ( 121 )中。
