Endogenous eukaryotic RNA-dependent RNA polymerases (RDRs) produce double-stranded RNA intermediates in diverse processes of small RNA synthesis in RNA silencing pathways. RDR6 is required in plants for posttranscriptional gene silencing induced by sense transgenes (S-PTGS) and has an important role in amplification of antiviral silencing. Whereas RDR1 is also involved in antiviral defense in p...

Posttranscriptional gene silencing (PTGS) of transgenes involves abundant 21-nucleotide small interfering RNAs (siRNAs) and low-abundance 22-nucleotide siRNAs produced from double-stranded RNA (dsRNA) by DCL4 and DCL2, respectively. However, DCL2 facilitates the recruitment of RNA-DEPENDENT RNA POLYMERASE 6 (RDR6) to ARGONAUTE 1-derived cleavage products, resulting in more efficient amplificati...

40 41 RNA quality control (RQC) eliminates aberrant RNAs based on their atypical structure, 42 whereas post-transcriptional gene silencing (PTGS) eliminates both aberrant and functional 43 RNAs through the sequence-specific action of short interfering RNAs (siRNAs). The 44 Arabidopsis thaliana mutant smd1b was identified in a genetic screen for PTGS deficiency, 45 revealing the involvement of S...

Double-stranded RNA induces potent and specific gene silencing through a process referred to as RNA interference (RNAi) or posttranscriptional gene silencing (PTGS). RNAi is mediated by RNA-induced silencing complex (RISC), a sequence-specific, multicomponent nuclease that destroys messenger RNAs homologous to the silencing trigger. RISC is known to contain short RNAs ( approximately 22 nucleot...

Posttranscriptional gene silencing (PTGS) is a sequence-specific mRNA degradation caused by small RNA, such as microRNA (miRNA) and small interfering RNA (siRNA). miRNAs are generated from MIRNA loci, whereas siRNAs originate from various sources of double-stranded RNA. In this study, an artificial RNA silencing inducible sequence (RSIS) was identified in rice (Oryza sativa). This sequence caus...

1063 www.sciencemag.org SCIENCE VOL 293 10 AUGUST 2001 E pigenetics covers a broad range of effects, and several are discussed in this special issue. But how did epigenetic regulation arise? For RNA-mediated silencing and DNA methylation there is evidence that they have evolved as part of a host defense mechanism against viruses and parasitic DNA.* The substrate—double-stranded RNA (dsRNA)—for ...

In Neurospora crassa, sequence-specific inhibition of endogenous genes can be induced by the introduction of transgenic DNA homologous to the target gene, through the mechanism of post-transcriptional gene silencing (PTGS) known as quelling. The application of this strategy to inactivate genes in N. crassa has, to date, been restricted by a limited silencing efficiency and instability of the si...

In the studies of plant infections, the plant immune response is known to play an essential role. In this paper we derive and analyse a new mathematical model of plant immune response with particular account for post-transcriptional gene silencing (PTGS). Besides biologically accurate representation of the PTGS dynamics, the model explicitly includes two time delays to represent the maturation ...

Plant Dicer-like (DCL) enzymes exhibit a GC-preference during anti-viral post-transcriptional gene silencing (PTGS), delivering an evolutionary selection pressure resulting in plant viruses with GC-poor genomes. However, some viruses, e.g. Turnip Yellow Mosaic Virus (TYMV, genus Tymovirus) have GC-rich genomes, raising the question as to whether or not DCL derived selection pressure affects the...

BACKGROUND Cell-fate determination requires that cells choose between alternative developmental pathways. For example, germ cells in the nematode worm Caenorhabditis elegans choose between mitotic and meiotic division, and between oogenesis and spermatogenesis. Germ-line mitosis depends on a somatic signal that is mediated by a Notch-type signaling pathway. The ego-1 gene was originally identif...