植物转基因座位形成的分子机制

Molecular Mechanisms of Transgenic Loci Formation in Plants

转基因座位是指染色体上插入的转基因及相邻的特定DNA序列。大多数转基因座位是以转基因片段、基因组片段和填充DNA相间而存在,仅少数含有完整的单拷贝转基因,这是由于在转基因整合过程中,转基因及基因组DNA发生缺失、重复和染色体的重排。转基因整合主要通过双链DNA断裂修复中的异常重组所产生,而同源重组也发挥了一定的作用。异常重组主要由单链复性、合成依赖链复性和依赖Ku蛋白的非同源末端连接途径调节。

Transgene locus is composed of transgene and its integration site in genomic DNA. Most transgene loci were composed of interspersed fragments of transfer DNA, genomic DNA and filler DNA except a few consisted of intact singlecopy of transgene. Analysis to the flanking sequences of the transgenic loci indicated that there were deletion, duplication and chromosomal rearrangement of transgene and genomic DNA. The transgene was integrated into chromosome through DNA double-strand break repair process preferentially by illegitimate recombination. The homologous recombination also played a role in transgene integration. The illegitimate recombination was mediated by single-strand annealing, synthesisdependent strand annealing and Ku-dependent non-homologous end-joining.