植物基因工程中的转基因沉默机制

Mechanism of Transgene Silencing in Plants Gene Engineering

植物转基因沉默可以发生在染色体DNA、转录和转录后三种不同的层次上，转录水平基因沉默机制涉及DNA甲基化、位置效应、重复序列、同源序列等作用。转录后水平基因沉默机制常用RNA域值模型、异常RNA模型、双链RNA模型、未成熟翻译终止模型等解释。目前没有一种通用的模型可以解释所有的转基因沉默现象，但不同模型从不同方面解释了转基因机制的某些方面。

Transgene silencing in plants can occour on the levels of chromosome DNA, transcription and posttran-scription. The mechanism of transcriptional gene silencing is related to DNA methylation, effect position, repeat sequence and homology sequence etc. Several possible mechanisms have been presented to explain the mechanism of post transcriptional gene silencing,such as RNA threshold model ,aberrant RNA model, double-strand RNA model and premature terminate translation model. Although there is no one universal model which could explain all the phenomena of transgene silencing, different models explain the mechanism of transgene silencing certain aspects from different aspects.