植物中转基因的整合机制

The Integration Mechanism of Exotic Gene into Plant Genome

转基因在植物基因组中的整合分两步 :在整合前阶段 ,转化的完整质粒及转基因片段经重组连接形成转基因串联子 (transgenearray) ,其中不含任何植物基因组序列 ,连接反应由植物细胞本身的酶催化 ,仅依赖于游离的DNA末端 ,CaMV35S启动子和T DNA边界序列中的特定序列可能充当重组热点 ;在整合阶段 ,转基因DNA通过微同源介导的异常重组整合到植物基因组中 ,最初的整合位点作为整合热点 ,引导随后的转基因分子在该位点附近整合 ,不同转基因位点可被1～ 1 0kb植物DNA隔开 ,形成转基因簇 (transgenecluster)。

There are two phases for transgene integrating into plant genome:In the preintegration phase,the plasmid and transgene fragments are recombinated and linked to make “transgene array'.The linkage reaction is catalyzed by the enzymes of plant cell and only determined by the free DNA tails,The special sequences in CaMV35S promoter and T-DNA may act as recombination hot spots; In the integration phase,transgene DNA integrates into plant genome through illegitimate recombination mediated by microhomologue.The fist integration site of transgene acts as integration hot spot and stimulates the following transgenes or transgene arrays to integrate into the local area.The different transgenes integration sites are separated by 1～10kb plant genome DNA and make up “transgene cluster'. ;