Epigenetic silencing in transgenic plants

Abstract

Epigenetic silencing is a natural phenomenon in which the expression of genes is regulated through modifications of DNA, RNA, or histone proteins. It is a mechanism for defending host genomes against the effects of transposable elements and viral infection, and acts as a modulator of expression of duplicated gene family members and as a silencer of transgenes. A major breakthrough in understanding the mechanism of epigenetic silencing was the discovery of silencing in transgenic tobacco plants due to the interaction between two homologous promoters. The molecular mechanism of epigenetic mechanism is highly complicated and it is not completely understood yet. Two different molecular routes have been proposed for this, that is, transcriptional gene silencing, which is associated with heavy methylation of promoter regions and blocks the transcription of transgenes, and post-transcriptional gene silencing (PTGS), the basic mechanism is degradation of the cytosolic mRNA of transgenes or endogenous genes. Undesired transgene silencing is of major concern in the transgenic technologies used in crop improvement. A complete understanding of this phenomenon will be very useful for transgenic applications, where silencing of specific genes is required. The current status of epigenetic silencing in transgenic technology is discussed and summarized in this mini-review.

Improvement of Salinity Stress Tolerance in Rice: Challenges and Opportunities

“…Unlike TGS however, PTGS is often reversible and used as a quick acting regulator of transcript half-life and subsequent gene expression [152]. The molecular processes of both TGS and PTGS have both been well characterized and are not in the scope of this review, and for further information please see the review by Rajeekumar et al [153]. Numerous studies have also reported transgene silencing in rice [154][155][156].…”

Selective gene dosage by CRISPR‐Cas9 genome editing in hexaploid Camelina sativa

“…These limitations could be overcome by genetic modifications that allow the dominant expression of a transgene carrying the desired trait or allele, or alternatively the dominant down‐regulation of endogenous genes by silencing. Down‐regulation strategies, albeit efficient, may pose problems in the long run since the endogenous genes are still expressed, leading to potential instability of the desired trait after several generations (Rajeevkumar et al ., 2015). Recently, the development of genome‐editing strategies allowed selective site‐directed mutagenesis even in large polyploid genomes, providing a very attractive approach to creating new stable alleles in crops.…”

Targeting intracellular transport combined with efficient uptake and storage significantly increases grain iron and zinc levels in rice

“…Transgenic plants with an inverted transgene repeat could be problematic, both from a practical and from regulatory point of view. First, two or more insertions of transgenes often result in epigenetic transgene silencing in subsequent plant generations (Kumpatla and Hall, ; Rajeevkumar et al ., ). Second, using an inverted transgene cassette repeat in breeding programs or crop production would require a regulatory approval of uncertain, but likely negative outcome.…”