David Baulcombe

..We are now in a good position to investigate the full extent of this functional diversity in genetic and epigenetic mechanisms of genome control...

..These findings reveal an unexpected level of complexity in the RNA silencing pathway in plants that may also apply in animals...

..This unit describes an isotope-free small-RNA cloning procedure that utilizes unmodified small RNAs and is routinely used to characterize small RNAs from various plant tissues...

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..The antiviral role of silencing might also apply in animals because a suppressor of silencing encoded by an insect virus was identified recently...

..According to this idea, the secondary siRNAs mediate RNA silencing as an immediate response that slows down the systemic spreading of the virus into the growing point and newly emerging leaves...

..According to this proposal, in the absence of these ESP proteins, these RNAs have aberrant 3' termini. The aberrant RNAs would enter the RNA silencing pathways because they are converted into dsRNA by RNA-dependent RNA polymerases...

..RNA silencing of ribulose-1,5-bisphosphate carboxylase/oxygenase and phytoene desaturase was not associated with the spreading of RNA targeting or DNA methylation, indicating that these endogenous RNAs are not templates for SDE1/SGS2...

..We further demonstrate that VIGS is a useful approach to dissect resistance signaling pathways in a genetically intractable plant species...

..We interpret the effect of polymerase IVa and trans-acting siRNA pathway mutations in terms of a modular property of RNA silencing pathways...

..The ability of P0 to block silencing without affecting signal movement may contribute to the phloem restriction of viruses in the Polerovirus group...

..We propose that FCA and FPA regulate chromatin silencing of single and low-copy genes and interact in a locus-dependent manner with the canonical small interfering RNA-directed DNA methylation pathway to regulate common targets...

..The strong responses in the phloem suggest a role of miRNAs in systemic information transfer via this long-distance transport system...

..From these findings, we infer that the role of PolIVb in siRNA production is secondary to a role in chromatin modification and is influenced by chromatin context...

..It is possible, based on analyses of short interfering RNA accumulation, that P25 suppresses silencing by interfering with either assembly or function of the effector complexes of RNA silencing...

..These methods and the underlying general principles also apply when VIGS is used in the analysis of other aspects of plant biology...

..We propose that miR159 is a phytohormonally regulated homeostatic modulator of GAMYB activity, and hence of GAMYB-dependent developmental processes...

..The results also indicate that, in addition to the previously recognized role in elicitor recognition, NB-LRR proteins may also function in downstream signaling pathways...

..They also suggest various ways that Tombusvirus suppressors can be used to investigate RNA silencing in plants and animals...

..This approach illustrates the potential benefits and limitations of RNA silencing in forward screens of gene function in plants...

..Our observations suggest that miRNAs play important regulatory roles in mosses...

..Our findings show that silencing SGT1 affects diverse types of disease resistance in plants and support the idea that R protein-mediated and nonhost resistance may involve similar mechanisms...

..This novel mechanism of meristem exclusion may be associated with the phenomenon of recovery in virus-infected plants in which upper leaves have little or no virus and are immune to secondary infection by the same virus...

..However activation of Rx is not simply release of negative regulation by the LRR and adjacent sequence because deleted forms of Rx that lack constitutive gain of function mutations are not active unless the protein is overexpressed...

..The common features of miRNAs and siRNAs in an alga and in higher plants indicate that complex RNA-silencing systems evolved before multicellularity and were a feature of primitive eukaryotic cells...

..These results implicate RanGAP-mediated cellular mechanisms, including nucleocytoplasmic trafficking, in the activation of disease resistance...

..However, protease activity was not sufficient because we found three elicitor-defective mutants in which there was a high level of protease activity in this assay...

..Thus, the VIGS system is an effective method of rapidly assessing gene function in potato...

..Taken together, our data indicate that contig13502 is a novel TAS locus and suggest a role for derived tasiRNAs in the regulation of gene expression in moss...

..The breadth of the disease-resistance phenotype from a natural R gene may be influenced by the tradeoff between the costs and benefits of broad-spectrum disease resistance...

..However, loss-of-function mutations in the RNBS-A motif and in the TIR domain retain the ability to oligomerize. From these results, we conclude that oligomerization is an early event in the N-mediated resistance to TMV...

..Silencing of gene #13 may reflect a novel strategy of TMV to suppress basal host defense mechanisms. The two-hybrid screenings did not identify tobacco proteins involved in helicase domain-induced N-mediated resistance...

..We propose that activation of Rx entails sequential disruption of at least two intramolecular interactions...