ABSTRACT The expression of a gene that encodes coat protein (CP) of Potato virus X (PVX) in transgenic tobacco plants confers a high level of CP-mediated rresistance (CP-MR) against PVX infection. To determine if posttranscriptional gene silencing (PTGS) plays a role in resistance, transgenic plants expressing PVX CP were challenged against PVX under conditions in which PTGS was suppressed by l...

In plants, transgenes can be silenced at both the transcriptional [1] and post-transcriptional levels [2]. Methylation of the transgene promoter correlates with transcriptional gene silencing (TGS) [3] whereas methylation of the coding sequence is associated with post-transcriptional gene silencing (PTGS) [4]. In animals, TGS requires methylation and changes in chromatin conformation [5]. The i...

BACKGROUND RNA interference (RNAi) in animals and post-transcriptional gene silencing (PTGS) in plants are related phenomena whose functions include the developmental regulation of gene expression and protection from transposable elements and viruses. Plant viruses respond by expressing suppressor proteins that interfere with the PTGS system. RESULTS Here we demonstrate that both transient an...

In plants, RNA silencing can be induced by highly transcribed sense transgenes (S-PTGS) or by transgene loci producing double-stranded RNA (dsRNA) due to the presence of inverted repeats (IR-PTGS). Both phenomena correlate with accumulation of 21-25 nt sense and anti-sense RNA homologous to the silent gene and with methylation of the coding sequence. We have challenged IR-PTGS with four viruses...

Post-transcriptional gene silencing (PTGS) of a green fluorescent protein (GFP) transgene is suppressed in Nicotiana benthamiana plants infected with potato virus Y (PVY) or with cucumber mosaic virus (CMV), but not in plants infected with potato virus X (PVX). By expressing PVY and CMV-encoded proteins in a PVX vector we have shown that the viral suppressors of gene silencing are the HCPro of ...

In plants, posttranscriptional gene silencing (PTGS) is an ancient and effective defense mechanism against viral infection. A number of viruses encode proteins that suppress virus-activated PTGS. The p19 protein of tombusviruses is a potent PTGS suppressor which interferes with the onset of PTGS-generated systemic signaling and is not required for viral replication or for viral movement in Nico...

Post-transcriptional gene silencing (PTGS) is a homology-dependent process that reduces cytoplasmic RNA levels. In several experimental systems, there is also an association of PTGS with methylation of DNA. To investigate this association, we used plants carrying a transgene encoding the green fluorescent protein (GFP). Gene silencing was induced using potato virus X RNA vectors carrying parts ...

Post-transcriptional gene silencing (PTGS) agents such as ribozymes, RNAi and antisense have substantial potential for gene therapy of human retinal degenerations. These technologies are used to knockdown a specific target RNA and its cognate protein. The disease target mRNA may be a mutant mRNA causing an autosomal dominant retinal degeneration or a normal mRNA that is overexpressed in certain...

In plants, post-transcriptional gene silencing (PTGS) spreads systemically, being transmitted from the silenced stock to the scion expressing the corresponding transgene. It has been reported that a graft-transmitted siRNA signal can also induce PTGS of an endogenous gene, but this was done by top-grafting using silenced stock. In the present study involving grafting of Nicotiana benthamiana, w...

Post-transcriptional gene silencing (PTGS) is a homology-dependent RNA degradation process that may target RNA exclusively in the cytoplasm. In plants, PTGS functions as a natural defense mechanism against viruses. We reported previously that the 2b protein encoded by cucumber mosaic cucumovirus (CMV) is a virulence determinant and a suppressor of PTGS initiation in transgenic Nicotiana bentham...