遗传转化植物中沉默基因的消除  

Reacting the Silencing Genes in the Transgenic Plants

作　　者：邹永梅[1] 施季森[1] 诸葛强[1] 黄敏仁[1] 

机构地区：[1]南京林业大学林木遗传和基因工程重点实验室,南京210037

出　　处：《分子植物育种》2006年第1期95-102,共8页Molecular Plant Breeding

基　　金：国家林业局2003年度重点课题基金项目（2003-002-L0）部分资助.

摘　　要：随着基因技术在生物科学许多领域的深入开展,转基因沉默问题已引起越来越多的科技工作者的关注。大量转基因植物的研究证明许多因素与基因沉默有关,植物遗传转化中外源基因的整合具有很大的随机性,外源基因的沉默也表现出多种多样的形式,转基因生物的外源基因的沉默可由多种机理造成。外源基因以多拷贝整合到植物细胞基因组中,会发生失活;基因沉默与整合的位点也密切相关,如果整合到转录活跃的常染色体上,毗邻寄主基因的调控系统系列将会影响外源基因的表达;如果插入到重复DNA或异染色质区,外源基因可能会失活;基因沉默并非在每一个发育时期,每一个细胞中总发生,有的外源基因,在幼苗阶段表达是正常的,但萌发到一定阶段后基因表现沉默。转基因沉默通常分为两大类:一类是转录水平上的基因沉默,另一类是转录后的基因沉默。前者是发生在核内的时间,而后者是发生在细胞质中。两者都与甲基化有关,转录水平上的基因沉默主要发生在启动子区域,基因的转录受抑制;而在转录后的基因沉默中,甲基化主要发生在基因的编码区,基因能够转录,产生mRNA,但mRNA在细胞质中被特异性地降解,不能正常翻译成蛋白质造成的,转录后基因沉默发生在细胞质中,转录物能在细胞核中积累但在细胞质中mRNA迅速降解或不能正常地加工。二者在时间上并非简单的前后关系,在空间上也不因为核膜的存在而相互隔离。本文对转基因植物中外源基因沉默的机制,如何降低外源基因的沉默可能性,以提高外源基因的表达率,以及通过DNA糖基化酶等方法适当处理,激活已经沉默的基因等问题进行了评述。With the development of gene technology in many domains of biology science in depth, the gene silencing on the transgenic plants has aroused more and more interest in researchers. A multitude of approaches indicates that many factors are concerned in gene silencing. The integration of extraneous genes in the process of plant genetic transformation is characteristically at random. And the extraneous gene silencing usually takes variegated forms, created by several mechanisms. The integration of the exogene into the host plant genome in multi-copied way, can cause gene silencing. Gene silencing is also closely associated with the integration locus; if the integration of the exogene occurs in the active euchromosome, the manipulating system of the adjacent host gene will be able to affect its expression; and provided that the exogene inserts into the duplicated DNA or heterochromatin, it will most likely be inactivated. Gene silencing, by no means, occurs through the whole developmental process or in each cell of plants. Some exogenes, though normally expressing in the seedling stage, appear their silencing in certain a stage afterwards. Gene silencing takes place both at transcriptional and post-transcriptional levels, abbr. to TGS and PTGS. TGS mainly occurs at promoter region, the gene transcription is usually suppressed thus; but as for PTGS, the methylation of DNA mainly occurs in the gene encoding area, wherein the gene can transcript into reRAN, yet specially degraded, which therefore, cannot normally translate into the protein. TGS and PTGS, occur neither in temporal sequence, nor sequester spatially with the existence of nuclear envelope. This paper reviews on promoting the transgenic expression by screening suitable transgenic and regulative element, applying advanced transformational methods, adopting more concise and quicker means to remove the DNA methylation by DNA glocosylases in plants.

关 键 词：植物 转基因沉默 沉默消除 

分 类 号：Q943.2[生物学—植物学]