The silencing of transgenes in transgenic plants.

Analysis of the large collection of genetically modified plants has shown that transgenes in a great of transgenic plants can^t be expressed as expected. In some cases, transgenes are inactive and the transgene expression couldn^t be detected throughly, which are called as gene silencing. Transgene silencing has greatly hinderred the application of the technic of plant gene transformation. Various factors seem to play a role, including of DNA methylation, transgene copy number and the DNA region where transgenes inserted. Basically there are two kinds of gene silencing, transcriptional gene silencing (TGS) and post-transcriptional gene silencing (PTGS). According to the study on a mount of transgenic plants, several possible mechanisms by which silencing is achieved have been presented, such as RdRP-cRNA, RNA threshold and RdDM models.