Project description:Background: Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5' cap structure and their subsequent 5M-bM-^@M-^Y to 3M-bM-^@M-^Y degradation. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA DEPENDENT RNA POLYMERASE 6 (RDR6). PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. Results: We show that that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of siRNAs, a subset of which depends on RDR6 for their production. Conclusions: Our results suggest that the decapping of aberrant endogenous RNA in P-bodies limits their entry into the PTGS pathway and prevents the subsequent deleterious consequences arising from this entry. We anticipate that the siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs that we coin rqc-siRNAs because they accumulate when RQC processes are impaired. Small RNA-seq experiments performed in duplicates for each condition.
Project description:Background: Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5' cap structure and their subsequent 5’ to 3’ degradation. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA DEPENDENT RNA POLYMERASE 6 (RDR6). PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. Results: We show that that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of siRNAs, a subset of which depends on RDR6 for their production. Conclusions: Our results suggest that the decapping of aberrant endogenous RNA in P-bodies limits their entry into the PTGS pathway and prevents the subsequent deleterious consequences arising from this entry. We anticipate that the siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs that we coin rqc-siRNAs because they accumulate when RQC processes are impaired.
Project description:Post-transcriptional gene silence (PTGS) is employed in plants to shut down transgenes, invading viral genes and a certain group of endogenous genes. Meanwhile, it is not clear how the risk of expansive PTGS from endogenous genes featured by transitive siRNA production is minimized. Here we demonstrate two essential components of the SKI complex in cytoplasmic 3’-5’ mRNA decay pathway, SKI2 and SKI3, function as negative regulators of transgene PTGS in Arabidopsis. The ski2 mutants manifested severe synthetic phenotypes with a 5’-3’ exoribonuclease mutant, ein5, which were substantially suppressed by the PTGS mutants, rdr6 and ago1. RDR6 is essential for the altered gene expression in ein5 ski2 on a transcriptome-wide scale. mRNA-seq approach was used to investigate the physiological relevance veiled by the myriad developmental phenotypes in Col-0 (C), ein5-1 (e), ski2-3 (s), ein5-1 ski2-3 (es), rdr6-11 (r) and rdr6-11 ein5-1 ski2-3 (res). A number of endogenous genes, including many miRNA target genes, manifest transitive 21-22 nt siRNA production and compromised gene expression in ein5 ski2 in an RDR6-dependent manner. Taken together, our study brings to light a dual-safeguard system in preventing the expansive siRNA production by the 5’-3’ and 3’-5’ cytoplasmic mRNA decay pathways.
Project description:Post-transcriptional gene silence (PTGS) is employed in plants to shut down transgenes, invading viral genes and a certain group of endogenous genes. Meanwhile, it is not clear how the risk of expansive PTGS from endogenous genes featured by transitive siRNA production is minimized. Here we demonstrate two essential components of the SKI complex in cytoplasmic 3 -5 mRNA decay pathway, SKI2 and SKI3, function as negative regulators of transgene PTGS in Arabidopsis. The ski2 mutants manifested severe synthetic phenotypes with a 5 -3 exoribonuclease mutant, ein5, which were substantially suppressed by the PTGS mutants, rdr6 and ago1. RDR6 is essential for the altered gene expression in ein5 ski2 on a transcriptome-wide scale. mRNA-seq approach was used to investigate the physiological relevance veiled by the myriad developmental phenotypes in Col-0 (C), ein5-1 (e), ski2-3 (s), ein5-1 ski2-3 (es), rdr6-11 (r) and rdr6-11 ein5-1 ski2-3 (res). A number of endogenous genes, including many miRNA target genes, manifest transitive 21-22 nt siRNA production and compromised gene expression in ein5 ski2 in an RDR6-dependent manner. Taken together, our study brings to light a dual-safeguard system in preventing the expansive siRNA production by the 5 -3 and 3 -5 cytoplasmic mRNA decay pathways. In this experiment, we did three replicates in sequencing that help increase the power in identify the differentially represented genes.The sequencing depth was also increased. Therefore we identified more siRNA-generating loci than that in previous study (GSE52408) (441 vs. 200 loci). Examination of small RNA profiles in 4 genotypes with 3 biological replicates each.
Project description:The functional structure of all biologically active molecules is dependent on intra- and inter-molecular interactions. This is especially evident for RNA molecules whose functionality, maturation, and regulation requires formation of correct secondary structure through encoded base-pairing interactions. Unfortunately, intra- and inter-molecular base-pairing information is lacking for most RNAs. Here, we use high-throughput sequencing to interrogate all base-paired RNA in Arabidopsis thaliana, and identify ~200 new small (sm)RNA-producing substrates of RNA-DEPENDENT RNA POLYMERASE 6. Our comprehensive analysis of paired RNAs reveals conserved functionality within introns and both 5’ and 3’ untranslated regions (UTRs) of mRNAs, as well as a novel population of functional RNAs, many of which are the precursors of smRNAs. Finally, we identify intra-molecular base-pairing interactions to produce a genome-wide collection of RNA secondary structure models. These findings highlight the importance of base-paired RNAs in eukaryotes, and present an approach that should be widely applicable for the analysis of this key structural feature of RNA. Double-stranded (dsRNA) specific RNA sequencing (dsRNA-seq) in the unopened flowerbuds of wild-type col-0 plants and rdr6 mutant plants, including 2 samples of col-0 dsRNA (1X- or 2X- Ribominus-treated samples) and 1 sample of rdr6 dsRNA. Corresponding two smRNA libraries (smRNA-seq) of both wild-type col-0 plants and rdr6 mutant plants of the same tissue are also presented.
Project description:Post-transcriptional gene silence (PTGS) is employed in plants to shut down transgenes, invading viral genes and a certain group of endogenous genes. Meanwhile, it is not clear how the risk of expansive PTGS from endogenous genes featured by transitive siRNA production is minimized. Here we demonstrate two essential components of the SKI complex in cytoplasmic 3 -5 mRNA decay pathway, SKI2 and SKI3, function as negative regulators of transgene PTGS in Arabidopsis. The ski2 mutants manifested severe synthetic phenotypes with a 5 -3 exoribonuclease mutant, ein5, which were substantially suppressed by the PTGS mutants, rdr6 and ago1. RDR6 is essential for the altered gene expression in ein5 ski2 on a transcriptome-wide scale. mRNA-seq approach was used to investigate the physiological relevance veiled by the myriad developmental phenotypes in Col-0 (C), ein5-1 (e), ski2-3 (s), ein5-1 ski2-3 (es), rdr6-11 (r) and rdr6-11 ein5-1 ski2-3 (res). A number of endogenous genes, including many miRNA target genes, manifest transitive 21-22 nt siRNA production and compromised gene expression in ein5 ski2 in an RDR6-dependent manner. Taken together, our study brings to light a dual-safeguard system in preventing the expansive siRNA production by the 5 -3 and 3 -5 cytoplasmic mRNA decay pathways. In this experiment, we did three replicates in sequencing that help increase the power in identify the differentially represented genes.The sequencing depth was also increased. Therefore we identified more siRNA-generating loci than that in previous study (GSE52408) (441 vs. 200 loci).
Project description:In plants, tasiRNAs form a class of endogenous secondary siRNAs produced through the action of RNA-DEPENDENT-RNA-POLYMERASE-6 (RDR6) upon microRNA-mediated cleavage of non-coding TAS RNAs. In Arabidopsis thaliana, TAS1, TAS2 and TAS4 tasiRNA production proceeds via a single cleavage event mediated by 22nt-long or/and asymmetric miRNAs in an ARGONAUTE-1 (AGO1)-dependent manner. By contrast, tasiRNA production from TAS3 seems to follow the so-called ‘two-hit’ process, where dual targeting of TAS3, specifically mediated by the 21nt-long, symmetric miR390, initiates AGO7-dependent tasiRNA production. Interestingly, features for TAS3 tasiRNA production differ in other plant species and we show here that such features also enable TAS3 tasiRNA biogenesis in Arabidopsis, and that a single miR390 targeting event is, in fact, sufficient for this process, suggesting that the ‘one-hit’ model underpins all the necessary rudiments of secondary siRNA biogenesis from plant TAS transcripts. Further results suggest that the two-hit configuration likely enhances the fidelity of tasiRNA production and, hence, the accuracy of downstream gene regulation. Finally, we show that a ‘non-cleavable one-hit’ process allows tasiRNA production from both TAS1 and TAS3 transcripts, indicating that RDR6 recruitment does not require miRNA cleavage, nor does the recruitment, as we further show, of SUPRRESSOR-OF-GENE-SILENCING-3, indispensable for tasiRNA generation.
Project description:In plants, smRNAs are often derived from long double-stranded RNA (dsRNA) molecules synthesized by one of the six genomically-encoded RNA-dependent RNA Polymerase (RDR) proteins. However, the full complement of the RDR-dependent smRNAs and functions that these proteins and their RNA-binding co-factors play in plant RNA silencing has not been fully uncovered. To address this gap, we performed a global genomic analysis of all six RDRs and two of their co-factors to find new substrates for RDRs and targets of the resulting RDR-derived siRNAs to uncover new functions for these proteins in plants. Based on these analyses, we identified substrates for the three RDR clade proteins (RDR3 - 5), which had not been well-characterized previously. We also identified new substrates for the other three RDRs (RDR1, 2, and 6) as well as the RDR2 co-factor RNA-DIRECTED DNA METHYLATION 12 (RDM12) and the RDR6 co-factor SUPRESSOR OF GENE SILENCING 3 (SGS3). These findings revealed that the target substrates of SGS3 are not limited to those solely utilized by RDR6, but that this protein seems to be a more general co-factor for the RDR family proteins. Additionally, we found that RDR6 and SGS3 are involved in the production of smRNAs that target transcripts related to abiotic stresses including water deprivation, salt stress, and ABA response, and as expected the levels of these mRNAs are increased in rdr6 and sgs3 mutant plants. Correspondingly, plants that lack these proteins (rdr6 and sgs3 mutants) are hypersensitive to ABA treatment, tolerant to high levels of PEG8000, and have higher survival rate under salt treatment in comparison to wild-type (Col-0). In total, our analyses have provided an extremely data-rich resource for uncovering new functions of RDR-dependent RNA silencing in plants, while also revealing a previously unexplored link between the RDR6/SGS3-dependent pathway and plant abiotic stress responses.
Project description:Virus infection triggers widespread silencing of host genes by a distinct class of endogenous siRNAs in Arabidopsis This study constructed and sequenced two independent small RNA libraries from the upper uninoculated leaves of (i) WT Arabidopsis plants 14 d after mock inoculation and of (ii) rdr1 rdr6 plants 14 d after infection with Fny CMV-Δ2b, and one library each from the upper uninoculated leaves of (iii) WT, (iv) rdr1, and (v) rdr6 plants 14 d after infection with TuMV-GFP. Coimmunoprecipitation with FLAG- and HA-specific antibodies was used to obtain (vi,vii) AGO1 and (viii,ix) AGO2 complexes, respectively, from the FLAG-AGO1/ago1-36 and HA-AGO2 plants 14 d after infection with Fny CMV-Δ2b for extracting total loaded small RNAs for the construction and sequencing of small RNA libraries.
Project description:Secondary metabolites are involved in the plant stress response. Among these are scopolin and its active form scopoletin, which are coumarin derivatives associated with reactive oxygen species scavenging and pathogen defence. Here we show that in Arabidopsis thaliana, scopolin accumulation can be induced in the root by osmotic stress and in the leaf by low temperature stress. A genetic screen for altered scopolin levels in Arabidopsis thaliana identified a mutant compromised for scopolin accumulation in response to stress; the lesion was present in a homologue of THO1, the product of which contributes to the THO/TREX complex. The THO/TREX complex contributes to RNA silencing, supposedly by trafficking precursors of small RNAs. Mutants carrying defective THO and RDR6 genes were impaired with respect to scopolin accumulation in response to stress, suggesting a mechanism based on RNA silencing like the transacting small interfering RNA pathway which requires THO/TREX and RDR6 function.