Root cell layer specific AGO1-bound sRNA and total sRNA from Arabidopsis ktn1 mutant
ABSTRACT: We profiled total sRNA and root cell layer specific AGO1-bound sRNA in ktn1 mutant to study the role of KTN1 in miRNA non-cell autonomous activiy in Arabidopsis. Overall design: Total sRNA and sRNA from GFP-AGO1 IP in plants expression GFP-AGO1 under EN7 (Endodermis) and ACL5 (Metaxylem and procambia) were examined.
Project description:microRNAs (miRNA’s) regulation target gene expression, often transcription factors and as such control entire transcriptional networks. This control is important for various developmental transitions and stress responses in a wide range of eukaryotic organisms. While miRNA-mediated gene regulation has been investigated over time (temporal) and in whole organs or tissues in multiple different organisms highlighting their importance, there has been a distinct lack of focus on spatial resolution of miRNA biology. Here we present at cell-type specific resolution, miRNA loading and miRNA action within the Arabidopsis root. Our results for the first time demonstrate the multiple novel modes of miRNA action and illustrate the widespread nature of miRNA movement, at a genome scale within a complex eukaryotic organ. Overall design: 5 samples examined corresponding to FLAG-AGO1-IP for plants expressing FLAG-AGO1 under 5 specific root cell layer promoter (columella/pACR4, stele/pSHR, endodermis/pSCR, cortex/pCO2 and epidermis/pWER)
Project description:Argonaute (Ago) proteins function in RNA silencing as components of the RNA-induced silencing complex (RISC). In lower organisms, the small interfering RNA and miRNA pathways diverge due in part to sorting mechanisms that direct distinct small RNA (sRNA) duplexes onto specific Ago-RISCs. However, such sorting mechanisms appear to be lost in mammals. miRNAs appear not to distinguish among Ago1-4. To determine the effect of viral infection on the sorting system, we compared the content of deep-sequenced RNA extracted from immunoprecipitation experiments with the Ago1 and Ago2 proteins using Epstein-Barr virus (EBV)-infected cells. Consistent with previous observations, sequence tags derived from miRNA loci in EBV and humans globally associate in approximately equivalent amounts with Ago1 and Ago2. Interestingly, additional sRNAs, which have not been registered as miRNAs, were associated with Ago1. Among them, some unique sequence tags derived from tandem loci in the human genome associate exclusively with Ago1 but not, or rarely, with Ago2. This is supported by the observation that the expression of the unique sRNAs in the cells is highly dependent on Ago1 proteins. When we knocked down Ago1, the expression of the Ago1-specific sRNAs decreased dramatically. Most importantly, the Ago1-specific sRNAs bound to mRNAs and regulated target genes and were dramatically upregulated, depending on the EBV life cycle. Therefore, even in mammals, the sorting mechanism in the Ago1-4 family is functional. Moreover, the existence of Ago1-specific sRNAs implies vital roles in some aspects of mammalian biology.
Project description:Arabidopsis ARGONAUTE1 (AGO1) encodes the RNA slicer enzyme of the microRNA (miRNA) pathway and is regulated by miR168-programmed, AGO1-catalyzed mRNA cleavage. Here, we describe two additional regulatory processes required for AGO1 homeostasis: transcriptional coregulation of MIR168 and AGO1 genes, and posttranscriptional stabilization of miR168 by AGO1. Disrupting any of these regulatory processes by using mutations or transgenes disturbs a proper functioning of the miRNA pathway. In contrast, minor perturbation leads to fine-tuned posttranscriptional adjustment of miR168 and AGO1 levels, thereby maintaining a proper balance of other miRNAs, which, together with AGO1, control the mRNA levels of miRNA targets. We suggest that miR168 stabilization occurs at the level of silencing-complex assembly and that modulating the efficiency of assembling miRNA-programmed silencing complexes will also be important in other contexts.
Project description:The shoot apical meristem (SAM) comprises a group of undifferentiated cells that divide to maintain the plant meristem and also give rise to all shoot organs. SAM fate is specified by class III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors, which are targets of miR166/165. In Arabidopsis, AGO10 is a critical regulator of SAM maintenance, and here we demonstrate that AGO10 specifically interacts with miR166/165. The association is determined by a distinct structure of the miR166/165 duplex. Deficient loading of miR166 into AGO10 results in a defective SAM. Notably, the miRNA-binding ability of AGO10, but not its catalytic activity, is required for SAM development, and AGO10 has a higher binding affinity for miR166 than does AGO1, a principal contributor to miRNA-mediated silencing. We propose that AGO10 functions as a decoy for miR166/165 to maintain the SAM, preventing their incorporation into AGO1 complexes and the subsequent repression of HD-ZIP III gene expression. Homozygous T2 progeny of complemented plants expressing ago10-3;PAGO10-HF-AGO10 and ago1;PAGO1-HF-AGO1 were used for preparation of AGO complexes. Flower samples including floral buds, open flowers, and newly set siliques (1-2 day old) were collected for protein extraction and isolation of dual-tagged AGO complexes using a two-step affinity purification. The isolated AGO complexes were divided into two parts, one aliquot was used for sRNA extraction with Trizol reagent, whereas the other part was used for monitoring protein purity by Gelcode blue staining and western blot using a monoclonal anti-Flag antibody (Sigma) as previous described.
Project description:To systematically investigate viral sRNA production and sRNA-target interaction, we sequenced sRNAs from Tobacco Rattle Virus (TRV)-infected Nicotiana benthamiana at an early (1 week post infection) and late time point (3 weeks post infection). The N. benthamiana 16c plants were infected with TGS-inducing viruses (TRV-35S and TRV-35-2M) and PTGS-inducing viruses (TRV-GFP and TRV-GFP-2M), respectively. TRV-35S is a recombinant TRV containing a 120 nt segment of the 35S promoter. Its derivative, TRV-35S-2M, carrying single nucleotide substitutions (SNS) at every 10 nt within the 120 nt 35S target segment. Same strategy was used to create recombinant TRV-GFP and TRV-GFP-2M targeting GFP coding sequence. According to SNS content, sRNAs from TRV-35S-2M/TRV-GFP-2M infected plants can be separated to yield primary (containing SNSs) and secondary sRNAs (lacking SNSs). Wild Type TRV was used along as viral infection control. Libraries were indexed during PCR amplification (16 cycles) according to the Illumina protocol. See individual sample information for specific index primers used.
Project description:miRNAs silence gene expression by repressing translation and/or by promoting mRNA decay. AGO1 is a key protein required for miRNA-mediated gene silencing. In animal cells, mRNA degradation of partially complementary miRNA targets occurs via deadenylation by the CAF1-CCR4-NOT1 deadenylase complex, followed by decapping and subsequent exonucleolytic digestion. To determine how generally miRNAs trigger deadenylation, we compared mRNA expression profiles in D. melanogaster cells depleted of AGO1, CAF1 or NOT1. We show that approximately 45% of AGO1-targets are regulated by both CAF1 and NOT1, indicating deadenylation is a widespread effect of miRNA regulation.<br><br>We employed RNA interference using long double-stranded RNAs to deplete cultured S2 cells of AGO1 (CG6671, 2 independent samples), CAF1 (CG5684, 2 independent samples), or NOT1 (CG1884, 3 independent samples). Further, we used Affymetrix oligonucleotide microarrays to analyze expression profiles in these samples. We included the following controls: ?mock? RNAi treatment and GFP dsRNA treatment (3 and 2 independent samples, respectively).<br>
Project description:RNA silencing is a major antiviral defense mechanism in plants and invertebrates. Plant ARGONAUTE1 (AGO1) is pivotal in RNA silencing, and hence is a major target for counteracting viral suppressors of RNA-silencing proteins (VSRs). P0 from Turnip yellows virus (TuYV) is a VSR that was previously shown to trigger AGO1 degradation via an autophagy-like process. However, the identity of host proteins involved and the cellular site at which AGO1 and P0 interact were unknown. Here we report that P0 and AGO1 associate on the endoplasmic reticulum (ER), resulting in their loading into ER-associated vesicles that are mobilized to the vacuole in an ATG5- and ATG7-dependent manner. We further identified ATG8-Interacting proteins 1 and 2 (ATI1 and ATI2) as proteins that associate with P0 and interact with AGO1 on the ER up to the vacuole. Notably, ATI1 and ATI2 belong to an endogenous degradation pathway of ER-associated AGO1 that is significantly induced following P0 expression. Accordingly, ATI1 and ATI2 deficiency causes a significant increase in posttranscriptional gene silencing (PTGS) activity. Collectively, we identify ATI1 and ATI2 as components of an ER-associated AGO1 turnover and proper PTGS maintenance and further show how the VSR P0 manipulates this pathway.
Project description:Bacterial small regulatory RNAs (sRNAs) play a major role in the regulation of various cellular functions. Most sRNAs interact with mRNA targets via an antisense mechanism, modifying their translation and/or degradation. Despite considerable progresses in discovering sRNAs in Gram-positive bacteria, their functions, for the most part, are unknown. This is mainly due to difficulties in identifying their targets. To aid in the identification of sRNA targets in Gram-positive bacteria, we set up an in vivo method for fast analysis of sRNA-mediated post-transcriptional control at the 5? regions of target mRNAs. The technology is based on the co-expression of an sRNA and a 5? sequence of an mRNA target fused to a green fluorescent protein (GFP) reporter. The system was challenged on Staphylococcus aureus, an opportunistic Gram-positive pathogen. We analyzed several established sRNA-mRNA interactions, and in addition, we identified the ecb mRNA as a novel target for SprX2 sRNA. Using our in vivo system in combination with in vitro experiments, we demonstrated that SprX2 uses an antisense mechanism to prevent ecb mRNA translation initiation. Furthermore, we used our reporter assay to validate sRNA regulations in other Gram-positive organisms, Bacillus subtilis and Listeria monocytogenes. Overall, our method is broadly applicable to challenge the predicted sRNA-mRNA interactions in Gram-positive bacteria.