Gene silencing is the practice of having certain genes whose expression is not expressed or can be reduced by others. Gene silencing was first observed in transgenic plants, then in nematodes, fungi, hydroids, fruit flies and mammals. After entering the nucleus, foreign genes will be affected by a variety of factors, which can be divided into three types according to their different action mechanisms and levels: the position effect, transcriptional gene silencing (TGS) at the transcriptional level and transcriptional gene silencing (PTGS) at the post-transcriptional level. Gene silencing is an important pathway for gene expression regulation and a self-protective mechanism of organisms at the level of gene regulation. It is common in foreign DNA invasion, viral infection, DNA transposition and rearrangement.
