RNAi mediated gene silencing and it’s application for crop improvement: A review

Abstract

Gene silencing is a general term describing epigenetic processes of gene regulation. Gene silencing can occur during either transcription or translation and is often used in research. Gene silencing is considered a gene knockdown mechanism since the methods used to silence genes, such as RNAi, CRISPR, or siRNA, generally reduce the expression of a gene by at least 70% but do not completely eliminate it. It is a epigenetic process of gene regulation. It is used to describe the “switching off” of a gene by a mechanism other than genetic modification. The process to silence genes first begins with the entrance of a double stranded RNA (dsRNA) molecule into the cell, which triggers the RNAi pathway. The double stranded molecule is then cut into small double stranded fragments by an enzyme called Dicer. These small fragments, which include small interfering RNAs (siRNA) and microRNA (miRNA), are approximately 21-23 nucleotides in length. The fragments integrate into a multi subunit protein called the ‘RNA induced silencing complex’, which contains Argonaute proteins that are essential components of the RNAi pathway. RNAi is the key process of gene silencing. With RNAi, it would be possible to target multiple genes for silencing using a thoroughly-designed single transformation construct. Moreover, RNAi can also provide broad-spectrum resistance against pathogens with high degree of variability, like viruses.