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Arabidopsis AGO1 N-terminal Poly-Q domain promotes phase separation and association with stress granules during heat stress [RNA-seq]

ABSTRACT: In Arabidopsis thaliana, ARGONAUTE1 (AGO1) plays a central role in microRNA (miRNA) and small interfering RNA (siRNA)-mediated silencing. Nuclear AGO1 is loaded with miRNAs and exported to the cytosol where it associates to the rough ER to conduct miRNA-mediated translational repression, mRNA cleavage and biogenesis of phased siRNAs. These latter, as well as other cytosolic siRNAs, are loaded into cytosolic AGO1, but in which compartment this happens is not known. Moreover, the effect of stress on AGO1 localization is still unclear. Here, we show that heat stress (HS) promotes AGO1 protein accumulation, which co-localizes with components of the siRNA bodies and of stress granules (SGs). AGO1 does not need SGS3, a key component of siRNA bodies, to efficiently form condensates during HS. Instead, we found that the still poorly characterized N-terminal Poly-Q domain of AGO1, which contains a prion-like domain, is sufficient to undergo phase separation. Moreover, an exposure of 1 hour to HS only moderately affected AGO1 loading by miRNAs and target cleavage, suggesting that its localization in condensates protects AGO1 rather than promoting its activity in reprograming gene expression during stress. Collectively, our work shed new light on the impact of high temperatures on the main effector of RNA silencing in plants.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE239833 | GEO | 2024/01/30

REPOSITORIES: GEO

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Arabidopsis AGO1 N-terminal Poly-Q domain promotes phase separation and association with stress granules during heat stress [miRNA-seq]

Project description:In Arabidopsis thaliana, ARGONAUTE1 (AGO1) plays a central role in microRNA (miRNA) and small interfering RNA (siRNA)-mediated silencing. Nuclear AGO1 is loaded with miRNAs and exported to the cytosol where it associates to the rough ER to conduct miRNA-mediated translational repression, mRNA cleavage and biogenesis of phased siRNAs. These latter, as well as other cytosolic siRNAs, are loaded into cytosolic AGO1, but in which compartment this happens is not known. Moreover, the effect of stress on AGO1 localization is still unclear. Here, we show that heat stress (HS) promotes AGO1 protein accumulation, which co-localizes with components of the siRNA bodies and of stress granules (SGs). AGO1 does not need SGS3, a key component of siRNA bodies, to efficiently form condensates during HS. Instead, we found that the still poorly characterized N-terminal Poly-Q domain of AGO1, which contains a prion-like domain, is sufficient to undergo phase separation. Moreover, an exposure of 1 hour to HS only moderately affected AGO1 loading by miRNAs and target cleavage, suggesting that its localization in condensates protects AGO1 rather than promoting its activity in reprograming gene expression during stress. Collectively, our work shed new light on the impact of high temperatures on the main effector of RNA silencing in plants.

2024-01-30 | GSE239836 | GEO

Arabidopsis AGO1 N-terminal Poly-Q domain promotes phase separation and association with stress granules during heat stress [nanoPARE]

2024-01-30 | GSE239834 | GEO

FIERY1 promotes microRNA accumulation by suppressing rRNA-derived small interfering RNAs in Arabidopsis [miRNA-seq]

Project description:Plant microRNAs (miRNAs) associate with ARGONAUTE1 (AGO1) to direct post-transcriptional gene silencing and regulate numerous biological processes. Although AGO1 predominantly binds miRNAs in vivo, AGO1 also associates with endogenous small interfering RNAs (siRNAs). It is unclear whether the miRNA/siRNA balance affects miRNA activities. Here we report that FIERY1 (FRY1), which is involved in 5’-3’ RNA degradation, regulates miRNA abundance and function by suppressing the biogenesis of ribosomal RNA-derived siRNAs (risiRNAs). In mutants of FRY1 and the nuclear 5’-3’ exonuclease genes XRN2 and XRN3, we found that a large number of 21-nt risiRNAs were generated through an endogenous siRNA biogenesis pathway. The production of risiRNAs correlated with pre-rRNA processing defects in these mutants. We also show that these risiRNAs were loaded into AGO1, causing reduced loading of miRNAs. This study reveals a previously unknown link between rRNA processing and miRNA accumulation.

2019-10-08 | GSE126482 | GEO

FIERY1 promotes microRNA accumulation by suppressing rRNA-derived small interfering RNAs in Arabidopsis [RNA-seq]

2019-10-08 | GSE133411 | GEO

AGO2 protects Drosophila siRNAs and microRNAs from target-directed degradation, even in the absence of 2′-O-methylation

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2021-01-05 | GSE163938 | GEO

Arabidopsis thaliana AGO1 immunoprecipitated small RNA from Col0 plants transformed with a transgene expressing wild-type or a nuclear localized form of AGO1 fused to GFP.

Project description:Plant microRNAs undergo stepwise-nuclear maturation before engaging cytosolic sequence-complementary transcripts in association with the silencing-effector protein ARGONAUTE1(AGO1). How plant miRNAs translocate to the cytosol remains mysterious as does their cellular loading site(s) into AGO1. Here, we show that the N-termini of plant AGO1s contain a nuclear-localization (NLS) and nuclear-export signal (NES), which, in Arabidopsis thaliana (At) enables AtAGO1 nucleo-cytosolic shuttling in a Leptomycin-B-inhibited manner, diagnostic of CRM1(Expo1)/NES-dependent nuclear export. Nuclear-only AtAGO1 contains the same 2’O-methylated miRNA cohort as its nucleo-cytosolic counterpart, but specifically interacts with the miRNA loading-chaperone HSP90. AtAGO1 nucleo-cytosolic shuttling is required for mature miRNA translocation and for miRNA-mediated silencing. We propose that plant miRNAs are matured, methylated, loaded into AGO1 in the nucleus, and exported cytoplasmically as AGO1:miRNA complexes in a CRM1(Expo1)/NES-dependent manner.

2018-01-04 | GSE100395 | GEO

The Arabidopsis F-box protein FBW2 degrades AGO1 to avoid spurious loading of illegitimate small RNA

Project description:RNA silencing is a conserved mechanism in eukaryotes and is involved in development, heterochromatin maintenance and defense against viruses. In plants, ARGONAUTE1 (AGO1) protein plays a central role in both microRNA (miRNA) and small interfering RNA (siRNA)-directed silencing and its expression is regulated at multiple levels. Here, we report that the F-box protein FBW2 targets proteolysis of AGO1 by a CDC48-mediated mechanism. We found that FBW2 assembles an SCF complex that recognizes the MID-PIWI domain of AGO1 and requires its C-terminal domain containing a GW motif for AGO1 turnover. We showed that FBW2 has a preference for the unloaded and for some mutated forms of AGO1 protein. While FBW2 loss of function does not lead to strong growth or developmental defects, it significantly increases RNA silencing activity. Interestingly, under conditions in which small RNA production or accumulation is affected, the failure to degrade AGO1 in fbw2 mutants becomes more deleterious for the plant. Hence, we showed that the non-degradable AGO1 protein assembles high molecular complexes and binds illegitimate small RNA leading to the cleavage of new target genes that belong to stress responses and cellular metabolic processes. Therefore, the control of AGO1 homeostasis by ubiquitin ligases, plays an important quality control to avoid off-target cleavage.

2022-04-01 | PXD024840 | Pride

Local Translation in Nuclear Condensate Amyloid-bodies

Project description:We report that solid-like condensates Amyloid-bodies are hubs of stress-resistant local nuclear translation in cells responding to high temperature. RNA-seq. analysis of purified Amyloid-bodies confirms that HSF1-transcribed mRNAs accumulate in these solid-like condensates during stress.

2021-01-15 | GSE164846 | GEO

Degradome sequencing of Arabidopsis ago1-27 mutant

Project description:The goal of this study is to globally identify miRNA/siRNA cleavage sites on mRNAs in Arabidopsis wild type and ago1-27 mutant.

2017-10-23 | GSE84728 | GEO

High-pressure sprayed siRNAs influence the efficiency but not the profile of transitive silencing

Project description:In plants, small interfering RNAs (siRNAs) are a quintessential class of RNA interference (RNAi)-inducing molecules produced by the endonucleolytic cleavage of double stranded RNAs (dsRNAs). In order to ensure robust RNAi, siRNAs are amplified through a positive feedback mechanism called transitivity. Transitivity relies on RNA-DIRECTED-RNA POLYMERASE 6 (RDR6)-mediated dsRNA synthesis using siRNA-targeted RNA. The newly synthesized dsRNA is subsequently cleaved into secondary siRNAs by DICER-LIKE (DCL) endonucleases. Just like primary siRNAs, secondary siRNAs are also loaded into ARGONAUTE proteins (AGOs) to form an RNA-induced silencing complex (RISC) reinforcing the cleavage of the target RNA. Although the molecular players underlying transitivity are well established, the mode of action of transitivity remains elusive. In this study, we investigated the influence of primary target sites on transgene silencing and transitivity using the GFP-expressing Nicotiana benthamiana 16C line, high pressure spraying protocol (HPSP), and synthetic 22-nucleotide (nt) long siRNAs. We found that the 22-nt siRNA targeting the 3’ of the GFP transgene was less efficient in inducing silencing when compared to the siRNAs targeting the 5’ and middle region of the GFP. Moreover, sRNA sequencing of locally silenced leaves showed that the amount but not the profile of secondary RNAs is shaped by the occupancy of the primary siRNA triggers on the target RNA. Our findings suggest that RDR6-mediated dsRNA synthesis is not primed by primary siRNAs and that dsRNA synthesis appears to be generally initiated at the 3’ end of the target RNA.

2021-12-01 | GSE189777 | GEO

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