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玉米油中不饱和脂肪酸含量高达80％,但亚麻酸的含量甚少仅占0.4％～1.2％左右.为增加玉米油中亚麻酸含量,我们选用了在脂肪酸链的△12和△15位具有催化优势的来自Acanthamoeba castellanii的双功能去饱和酶AcD12基因.根据玉米密码子的偏好优化合成该基因序列,并构建了含有抗除草剂EPSP基因和花青素合成调控转录因子基因作为可视化筛选标记的玉米高效表达载体pBAC106,通过农杆菌介导进行玉米幼胚的转化.T0代转基因植株PCR鉴定结果表明含有AcD12基因和EPSP基因的T-DNA已经整合到玉米的基因组上,经过除草剂以及花青素可视化筛选的T1代转基因植株EPSP基因试纸条蛋白活性检测呈阳性.脂肪酸成分分析结果表明,与非转基因对照自交系京501相比,转基因植株叶片的亚麻酸的含量增加幅度在20％～50％,而相应的油酸、亚油酸均有所减少,减少幅度在10％～20％左右;种子中三种不饱和脂肪酸与对照相比均有大幅度的提高,其中亚油酸含量增加幅度最大,达到50％～200％,油酸其次,增加50％～120％,亚麻酸的增加幅度比油酸略小,在40％～100％之间.由此表明,AcD12基因在改良玉米脂肪酸成分、增加玉米油中亚麻酸的含量的效果明显.“,”The amount of unsaturated fatty acids in corn oil is up to 80％,but the level of linoleic acid is only about 0.4％～1.2％.To increase the content of linolenic acid in corn oil,a bifunctional △12,△15-Desaturase (AcD12) from A canthamoeba castellanii was used in this research.According to the maize preference codon,we optimized and synthesized A cD12 gene and constructed an efficient expression vector pBAC 106 which contain EPSP gene and anthocyanin synthesis transcription regulation factors gene as visual selection marker gene,and then transformed maize immature embryos via agrobacterium mediated transformation.PCR identification of T0 generation convinced that T-DNA containing EPSP and AcD12 genes had been integrated into the maize genome,and positive activity of EPSP protein tested by strip verified the expression of foreign EPSP gene after the screening by anthocyanin visual selection and herbicide resistance experiment of T1 generation.The analysis of fatty acid composition of transgenic plants showed that,compared with the inbred line Jing501,linolenic acid content in leaves increased in 20％～50％,and inversely,oleic acid and linoleic acid were decreased in 10％～20％.By contrast,in seeds,three types of unsaturated fatty acid are greatly improved.Among them,the content oflinoleic acid increased mostly,was 50％ ～200％,followed by oleic acid and linolenic acid,rose in 50％～ 120％ and 40％～100％,respectively.This study therefore demonstrates that the bifunctional desaturase A cD12 gene was significantly effective in improving the components of corn fatty acids and increasing the amount of linoleic acid in corn oil.