Double-stranded (ds) RNA causes the specific degradation of homologous RNAs in a process called "RNA interference (RNAi)"[1-4]; this process is called "posttranscriptional gene silencing (PTGS)" in plants [5-7]. Both classes of gene silencing have been reviewed extensively [8-13]. The duplex RNA becomes processed by Dicer [14] or another RNase III-like enzyme to short dsRNA fragments of about 2...

Several plant virus mutants, in which genes encoding silencing suppressor proteins have been deleted, are known to induce systemic or localized RNA silencing against themselves and other RNA molecules containing homologous sequences. Thus, it is thought that many cases of cross-protection, in which infection with a mild or asymptomatic virus mutant protects plants against challenge infection wi...

RNA silencing refers to small regulatory RNA-mediated processes that repress endogenous gene expression and defend hosts from offending viruses. As an anti-host defense mechanism, viruses encode suppressors that can block RNA silencing pathways. Cucumber mosaic virus (CMV)-encoded 2b protein was among the first suppressors identified that could inhibit post-transcriptional gene silencing (PTGS)...

Given their sessile condition, land plants need to integrate environmental cues rapidly and send signal throughout the organism to modify their metabolism accordingly. Small RNA (sRNA) molecules are among the messengers that plant cells use to carry such signals. These molecules originate from fold-back stem-loops transcribed from endogenous loci or from perfect double-stranded RNA produced thr...

Virus-induced RNA silencing is involved in plant antiviral defense and requires key enzyme components, including RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonaute proteins (AGOs). However, the transcriptional regulation of these critical components is largely unknown. In petunia (Petunia hybrida), an ethylene-responsive element binding factor, PhERF2, is i...

RNA 5-methyl and 5-propynyl pyrimidine analogs were substituted into short interfering RNAs (siRNAs) to probe major groove steric effects in the active RNA-induced silencing complex (RISC). Synthetic RNA guide strands containing varied combinations of propynyl and methyl substitution revealed that all C-5 substitutions increased the thermal stability of siRNA duplexes containing them. Cellular ...

Starting from a random RNA library expressed in yeast cells, we evolved an RNA-based transcriptional silencing domain with potency comparable to that observed when Sir1, a known silencing protein, is localized to a promoter. Using secondary-structure predictions and site-directed mutagenesis, we dissected the functional domains of the most active evolved RNA transcriptional silencer. Observed R...