Skills (4)
Publications (21) View all
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Article: Cytoplasmic and nuclear quality control and turnover of single-stranded RNA modulate post-transcriptional gene silencing in plants.
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ABSTRACT: Eukaryotic RNA quality control (RQC) uses both endonucleolytic and exonucleolytic degradation to eliminate dysfunctional RNAs. In addition, endogenous and exogenous RNAs are degraded through post-transcriptional gene silencing (PTGS), which is triggered by the production of double-stranded (ds)RNAs and proceeds through short-interfering (si)RNA-directed ARGONAUTE-mediated endonucleolytic cleavage. Compromising cytoplasmic or nuclear 5'-3' exoribonuclease function enhances sense-transgene (S)-PTGS in Arabidopsis, suggesting that these pathways compete for similar RNA substrates. Here, we show that impairing nonsense-mediated decay, deadenylation or exosome activity enhanced S-PTGS, which requires host RNA-dependent RNA polymerase 6 (RDR6/SGS2/SDE1) and SUPPRESSOR OF GENE SILENCING 3 (SGS3) for the transformation of single-stranded RNA into dsRNA to trigger PTGS. However, these RQC mutations had no effect on inverted-repeat-PTGS, which directly produces hairpin dsRNA through transcription. Moreover, we show that these RQC factors are nuclear and cytoplasmic and are found in two RNA degradation foci in the cytoplasm: siRNA-bodies and processing-bodies. We propose a model of single-stranded RNA tug-of-war between RQC and S-PTGS that ensures the correct partitioning of RNA substrates among these RNA degradation pathways.Nucleic Acids Research 03/2013; · 8.03 Impact Factor -
Article: The origin and effect of small RNA signaling in plants.
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ABSTRACT: 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 through the action of RNA-dependent RNA polymerases. Once produced, sRNAs associate with Argonaute (AGO) and other proteins to form the RNA-induced silencing complex (RISC) that executes silencing of complementary RNA molecules. Depending on the nature of the RNA target and the AGO protein involved, RISC triggers either DNA methylation or chromatin modification (leading to transcriptional gene silencing, TGS) or RNA cleavage or translational inhibition (leading to post-transcriptional gene silencing, PTGS). In some cases, sRNAs move to neighboring cells and/or to the vascular tissues for long-distance trafficking. Many genes are involved in the biogenesis of sRNAs and recent studies have shown that both their origin and their protein partners have great influence on their activity and range. Here we summarize the work done to uncover the mode of action of the different classes of sRNA with special emphasis on their movement and how plants can take advantage of their mobility. We also review the various genetic requirements needed for production, movement and perception of the silencing signal.Frontiers in plant science. 01/2012; 3:179. -
Chapter: Small RNA-Mediated Control of Development in Plants
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ABSTRACT: In the last decade, it became clear that RNA-RNA interactions are extremely important in the regulation of gene expression. Indeed, although a large portion of most eukaryotic genome is actively transcribed into RNA, only a small fraction encodes proteins. In many cases, long non-protein coding RNAs are processed into small RNAs, 20 to 30 nucleotides in length, which regulate gene expression through base pairing with complementary sense RNA. Such mechanisms fine tune regulate the expression of genes during development and serve as a flexible, sequence-specific, source of regulation that promotes adaptability in response to biotic and abiotic stresses. In this chapter, we review studies that uncovered the mode of action of the different classes of small RNAs during the development of plants.01/2013; -
Article: The miRNA pathway limits AGO1 availability during siRNA-mediated PTGS defense against exogenous RNA.
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ABSTRACT: In plants, most microRNAs (miRNAs) and several endogenous small interfering RNAs (siRNAs) bind to ARGONAUTE1 (AGO1) to regulate the expression of endogenous genes through post-transcriptional gene silencing (PTGS). AGO1 also participates in a siRNA-mediated PTGS defense response that thwarts exogenous RNA deriving from viruses and transgenes. Here, we reveal that plants supporting transgene PTGS exhibit increased levels of AGO1 protein. Moreover, increasing AGO1 levels either by mutating miRNA pathway components or, more specifically, by impairing miR168-directed regulation of AGO1 mRNA leads to increased PTGS efficiency, indicating that the miRNA pathway dampens the efficiency of PTGS, likely by limiting the availability of AGO1. We propose that during the transgene PTGS initiation phase, transgene siRNAs and endogenous siRNAs and miRNA compete to bind to AGO1, leading to a transient reduction in AGO1-miR168 complexes and a decline in AGO1 mRNA cleavage. The concomitant increase in AGO1 protein levels would facilitate the formation of AGO1-transgene siRNA complexes and the entry into the PTGS amplification phase. We suggest that the miRNA pathway imposes an important limitation on PTGS efficiency, which could help protect endogenous mRNAs from being routinely targeted by PTGS.Nucleic Acids Research 08/2011; 39(21):9339-44. · 8.03 Impact Factor -
Article: RNA-dependent RNA polymerase 6 delays accumulation and precludes meristem invasion of a viroid that replicates in the nucleus.
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ABSTRACT: The detection of viroid-derived small RNAs (vd-sRNAs) similar to the small interfering RNAs (siRNAs, 21 to 24 nucleotides [nt]) in plants infected by nuclear-replicating members of the family Pospiviroidae (type species, Potato spindle tuber viroid [PSTVd]) indicates that they are inducers and targets of the RNA-silencing machinery of their hosts. RNA-dependent RNA polymerase 6 (RDR6) catalyzes an amplification circuit producing the double-stranded precursors of secondary siRNAs. Recently, the role of RDR6 in restricting systemic spread of certain RNA viruses and precluding their invasion of the apical growing tip has been documented using RDR6-silenced Nicotiana benthamiana (NbRDR6i) plants. Here we show that RDR6 is also engaged in regulating PSTVd levels: accumulation of PSTVd genomic RNA was increased in NbRDR6i plants with respect to the wild-type controls (Nbwt) early in infection, whereas this difference decreased or disappeared in later infection stages. Moreover, in situ hybridization revealed that RDR6 is involved in restricting PSTVd access in floral and vegetative meristems, thus providing firm genetic evidence for an antiviroid RNA silencing mechanism. RNA gel blot hybridization and deep sequencing showed in wt and RDR6i backgrounds that PSTVd sRNAs (i) accumulate to levels paralleling their genomic RNA, (ii) display similar patterns with prevailing 22- or 21-nt plus-strand species, and (iii) adopt strand-specific hot spot profiles along the genomic RNA. Therefore, the surveillance mechanism restraining entry of some RNA viruses into meristems likely also controls PSTVd access in N. benthamiana. Unexpectedly, deep sequencing also disclosed in NbRDR6i plants a profile of RDR6-derived siRNA dominated by 21-nt plus-strand species mapping within a narrow window of the hairpin RNA stem expressed transgenically for silencing RDR6, indicating that minus-strand siRNAs silencing the NbRDR6 mRNA represent a minor fraction of the total siRNA population.Journal of Virology 12/2009; 84(5):2477-89. · 5.40 Impact Factor
