转基因植物转录后基因沉默机制及克服策略

Progress on the Post-transcriptional Gene Silencing Mechanism and Correspondent Strategy in Transgenic Plants

转录后基因沉默 (post transcriptionalgenesilencing,PTGS)表现为基因具有转录活性 ,能转录出mRNA ,但由于细胞启动了RNA特异降解机制 ,使mRNA特异水解或翻译有受抑制的现象。它常常诱发于外源基因的侵入和特定内源基因的表达 ,随后产生的siRNA和miRNA ,在多种酶类作用下 ,以 5′至 3′的方向降解相应RNA。PTGS沉默信号还能够以级联放大的形式扩散至整个植物体。在转基因植物中 ,利用已有的对沉默机制的认识去克服基因沉默 ,人们已提出一系列应对策略。就转基因植物转录后基因沉默在PTGS的诱发、mRNA降解或抑制、PTGS信号传导等方面机制的研究进展作一综述 ;并在克服基因沉默的诸多对策中 ,着重介绍在转基因DNA或转化载体的设计中可加入或删除的一些特殊序列。

Post transcriptional silencing is characterized by the phenomenon that the mRNA can be generated, but will be degraded instantly by a special system or inhibited in subsequent translation. It is often induced by some foreign gene, such as transgene, virus, transposon, or caused by some endo special non coded sequences. The degrading system involves the siRNA or miRNA, some enzyme and target mRNA, and the degrading orientation is 5′ 3′. PTGS can spread to all the plant body through the signals. In this text, transgenic plant PTGS scheme, which includes triggering, mRNA degrading or inhibition, and signal spreading, will be summarized; and the strategy for overcoming gene silencing are also concerned, focusing on some available DNA elements, such as gene silencing suppressor of virus, MAR, MOM, which can be used to devising of transgenic vector.