3 . the mechanism of dna integration mediated by homologous recombination in chloroplast transformation was tentatively explored . we isolated two chloroplast dna fragments from brassica napus and used them as targeting sequence to integr 成功地通过h次转化获得整合并表达多基因的转基因烟草,缩短了研究周期,对相关转基因植物的研究有一定参考价值。