Project description:Communication between interacting organisms via bioactive molecules is widespread in nature and plays key roles in diverse biological processes. Small RNAs (sRNAs) can travel between host plants and filamentous pathogens to trigger trans-kingdom RNA interference (RNAi) in recipient cells and modulate plant defense and pathogen virulence. However, how trans-kingdom RNAi is regulated has rarely been reported. Here, we show that the secretory protein VdSSR1 (secretory silencing repressor 1) from Verticillium dahliae, a soil-borne phytopathogenic fungus that causes wilt diseases in a wide range of plant hosts, is required for fungal virulence in plants through the suppression of trans-kingdom RNAi.
Project description:This project aims to identify novel protein partners of conserved trans-sRNAs in the α-proteobacterium Sinorhizobium meliloti. Trans-sRNAs (AbcR2, NfeR1 and EcpR1) were tagged at their 5’ ends with the MS2 aptamer. To identify the proteins associated with the trans-sRNAs we: i) expressed and purified the MS2 coat protein fused to maltose-binding protein (MS2-MBP); ii) purified MS2 tagged sRNAs conjugated with MS2-MBP via amylase column; and iii) subjected retained proteins to mass spectrometry analysis. To discard unspecific interactions we also analysed several control samples: i) samples expressing untagged trans-sRNAs; ii) samples expressing an MS2 tagged Rho-independent transcriptional terminator.
Project description:Transgenic Arabidopsis plants (AGO2::HA:AGO2) were treated with either mock (10 mM MgCl2) or Pseudomonas syringae pv. tomato (Pst) expressing avrRpt2 (R2) at a concentration of 2 x 107 cfu/ml for 14 hours. sRNAs associated with AGO1 and AGO2 were co-immunoprecipitated using antibodies against either AGO1 (AGO1-IP), or HA (hemagglutinin) (AGO2-IP). As controls, we also gel-purified the 18-28 nt fraction of the total RNAs from an AGO2 mutant (ago2-1). The co-immunoprecipitated or gel-purified RNAs were cloned and sequenced by Illumina deep sequencing. Examination of AGO-associated sRNAs in pathogen-treated or control plants
Project description:Conventional RNA interference (RNAi) pathways suppress eukaryotic gene expression at the post-transcriptional or transcriptional level. At the core of RNAi are small RNAs (sRNAs) and effector Argonaute proteins. Arabidopsis AGO1 is known to bind microRNAs (miRNAs) and post-transcriptionally repress target genes via mRNA cleavage and/or translational inhibition in the cytoplasm. Here, we report that AGO1 binds to the chromatin of transcriptionally active genes and promotes their transcription. We show that sRNAs and SWI/SNF are required for AGO1 binding to chromatin and its function in promoting gene transcription. Moreover, we show that various stimuli including plant hormones and stresses specifically trigger AGO1 binding to the stimulus-responsive genes. Finally, we show that AGO1 facilitates the induction of genes in the jasmonate (JA) signaling pathways and the activation of JA responses. Our findings reveal an unsuspected role for AGO1 in facilitating gene transcription in response to plant hormones and stresses.
Project description:Transgenic Arabidopsis plants (AGO2::HA:AGO2) were treated with either mock (10 mM MgCl2) or Pseudomonas syringae pv. tomato (Pst) expressing avrRpt2 (R2) at a concentration of 2 x 107 cfu/ml for 14 hours. sRNAs associated with AGO1 and AGO2 were co-immunoprecipitated using antibodies against either AGO1 (AGO1-IP), or HA (hemagglutinin) (AGO2-IP). As controls, we also gel-purified the 18-28 nt fraction of the total RNAs from an AGO2 mutant (ago2-1). The co-immunoprecipitated or gel-purified RNAs were cloned and sequenced by Illumina deep sequencing.
Project description:Efforts to catalogue eukaryotic transcripts have uncovered a set of species derived from the termini and exon/intron boundaries of protein-coding loci. The biogenesis pathways of these small RNAs (sRNAs) are largely unknown, but a mechanism depending on backtracking of RNA polymerase II (RNAPII) has been suggested. Moreover, the functional relevance, if any, of these sRNAs remains elusive. By sequencing 12-100nt transcripts from cells depleted of major RNA degradation enzymes as well as RNAs associated with the effector-proteins Argonaute (AGO) 1/2, we provide mechanistic models for sRNA production and utilization. We suggest that neither splice site associated (SSa)- nor transcription start site associated (TSSa)-RNAs arise from RNAPII backtracking. Instead SSa-RNAs are largely degradation products of mRNA splicing intermediates, while TSSa-RNAs likely derive from nascent RNA protected by stalled RNAPII against nucleolysis. We also reveal new AGO1/2-associated RNAs, including such derived from 3'ends of introns (5'tailed miRtrons) and from mRNA 3'UTRs. Interestingly, both appear to draw from non-canonical microRNA (miRNA) biogenesis pathways. 10 samples all from HeLa in three size ranges: 12-20, 18-30 and 30-100. 1 from 12-20: nuclear; 6 from 18-30: WT, nuclear, RRP40 knockdown, Ago1&2 IP, RRP40 knockdown and Ago1&2 IP, XRN1&2 knockdown; 3 from 30-100: WT, of RRP40 knockdown, XRN1&2 knockdown.
Project description:Phytophthora spp. encode large sets of effector proteins and distinct populations of small RNAs (sRNAs). Reports suggest that pathogen-derived sRNAs can modulate the expression of plant defense genes. The experiments reported here were designed to shed light on impact of sRNAs in the potato-P. infestans interaction. We used the Argonaute or Ago1 from P. infestans tagged with GFP transformed into the 88069 strain to infect potato cv. Bintje plants. Collected leaf materials were used in co-immunoprecipitation experiments together with P. infestans harboring GFP (control GFP) and P. infestans mycelia grown on media (control mycelia). These three materials were sequenced at a Ion Proton platform. The reads length of 8-38 nt were adaptor-trimmed and mapped to the P. infestans genome and the Solanom tuberosum genome v4.04. Both P. infestans-associated and potato derived sRNAs were identified.
Project description:RNA silencing is one of the main defense mechanisms employed by plants to fight viruses. In change, viruses have evolved silencing suppressor proteins to neutralize antiviral silencing. Since the endogenous and antiviral functions of RNA silencing pathway rely on common components, it was suggested that viral suppressors interfere with endogenous silencing pathway contributing to viral symptom development. In this work, we aimed to understand the effects of the tombusviral p19 suppressor on endogenous and antiviral silencing during genuine virus infection. We showed that ectopically expressed p19 sequesters endogenous small RNAs (sRNAs) in the absence, but not in the presence of virus infection. Our presented data question the generalized model in which the sequestration of endogenous sRNAs by the viral suppressor contributes to the viral symptom development. We further showed that p19 preferentially binds the perfectly-paired ds-viral small interfering RNAs (vsiRNAs) but does not select based on their sequence or the type of the 5’ nucleotide. Finally, co-immunoprecipitation of sRNAs with AGO1 or AGO2 from virus-infected plants revealed that p19 specifically impairs vsiRNA loading into AGO1 but not AGO2. Our findings, coupled with the fact that p19-expressing wild type Cymbidium ringspot virus (CymRSV) overcomes the Nicotiana benthamiana silencing based defense killing the host, suggest that AGO1 is the main effector of antiviral silencing in this host-virus combination. To further support our hypothesis we investigate whether the ability of p19 to bind endogenous sRNA without virus infection has biological important impact on endogenous pathways and is this reduced if the virus is present. To asses this we made mRNA sequencing from mock inoculated and Cym19stop infected p19syn plants. Cym19stop infected wild type plant was sequenced as a control. The sequencing data results supports our claims. An increase in transcriptional levels were found in case of genes known to be under small RNA regulation in uninfected p19syn plants and expressional levels return to normal Cym19stop p19syn plants.
Project description:Small non-coding RNAs (sRNAs) play key roles in plant development, growth and responses to biotic and abiotic stresses. At least four classes of sRNAs have been well characterized in plants, including repeat-associated siRNAs (rasiRNAs), microRNAs (miRNAs), trans-acting siRNAs (tasiRNAs) and natural antisense transcript-derived siRNAs. Chinese fir (Cunninghamia lanceolata) is one of the most important coniferous evergreen tree species in China. No sRNA from Chinese fir has been described to date. To obtain sRNAs in Chinese fir, we sequenced a sRNA library generated from seeds, seedlings, leaves, stems and calli, using Illumina high throughput sequencing technology. A comprehensive set of sRNAs were acquired, including conserved and novel miRNAs, rasiRNAs and tasiRNAs. With BLASTN and MIREAP we identified a total of 115 conserved miRNAs comprising 40 miRNA families and one novel miRNA with precursor sequence. The expressions of 16 conserved and one novel miRNAs and one tasiRNA were detected by RT-PCR. Utilizing real time RT-PCR, we revealed that four conserved and one novel miRNAs displayed developmental stage-specific expression patterns in Chinese fir. In addition, 209 unigenes were predicted to be targets of 30 Chinese fir miRNA families, of which five target genes were experimentally verified by 5' RACE, including a squamosa promoter-binding protein gene, a pentatricopeptide (PPR) repeat-containing protein gene, a BolA-like family protein gene, AGO1 and a gene of unknown function. We also demonstrated that the DCL3-dependent rasiRNA biogenesis pathway, which had been considered absent in conifers, existed in Chinese fir. Furthermore, the miR390-TAS3-ARF regulatory pathway was elucidated. We unveiled a complex population of sRNAs in Chinese fir through high throughput sequencing. This provides an insight into the composition and function of sRNAs in Chinese fir and sheds new light on land plant sRNA evolution.