Biology subjects

Bouteiller, N.

Publications and source records attributed to Bouteiller, N..

5 recordsLinked to original sources

bioRxiv2026

Distinct thresholds condition sense PTGS initiation and amplification.

It has long been known that Pro35S-driven sense transgenes have a high propensity to undergo post-transcriptional gene silencing (S-PTGS). However, what exactly conditions S-PTGS initiation and amplification to make it systemic remains unknown. Through genetic screens, we show that antagonistic chromatin-related mutations enhancing and reducing transgene expression, result in enhanced and reduced S-PTGS amplification capacities, respectively, without affecting the initiation rate. Analysis of a large set of independent transgenic plants confirm a direct relationship between transgene expression and its capacity to amplify S-PTGS. Combining an inducible or a tissue-specifically expressed GUS transgene with a Pro35S:GUS transgene locus prone to amplify S-PTGS but unable to spontaneously initiate it induces systemic S-PTGS, indicating that transient and/or local passing of a discrete threshold is sufficient to initiate S-PTGS. Together, these results call for the existence of distinct thresholds related to transiently produced aberrant RNA and permanently produced target mRNA levels, which condition S-PTGS initiation and amplification, respectively. We show that this model also applies to endogenous genes for which RNA Quality Control (RQC) acts as a first layer of protection against S-PTGS, and DCL2s obscuration by DCL4 as a second layer, allowing RQC to dysfunction locally without translating into the drama of systemic S-PTGS.

plant biology↗

bioRxiv2025

The tryptophan-binding pockets of Arabidopsis AGO1 facilitate amplified RNA interference via SGS3

ARGONAUTE (AGO) proteins associate with small RNAs to form RNA-induced silencing complexes (RISCs). Arabidopsis AGO1 effects post-transcriptional silencing by microRNAs (miRNAs) and small interfering RNAs (siRNAs) and is necessary for siRNA amplification through conversion of RISC target RNAs into double-stranded RNA by the RNA-dependent RNA Polymerase RDR6 and its mandatory cofactors SGS3 and SDE5. Many AGO proteins harbor hydrophobic pockets that interact with tryptophan residues, often surrounded by glycine (GW/WG), in intrinsically disordered regions (IDRs) of RISC cofactors. Here, we show that GW/WG dipeptides in the IDR of SGS3 and the hydrophobic pockets in AGO1 are required for fully functional RDR6-dependent siRNA amplification. We also show that this mechanism requires AGO1-specific structural elements, including positively charged residues surrounding the binding pockets, and a conserved, negatively charged patch in the IDR of SGS3. Thus, the same, conserved protein-protein interaction site is used for different purposes in distinct eukaryotic AGO proteins: the GW/WG-mediated TNRC6-Ago2 interaction is crucial for miRNA-guided silencing in metazoans whereas the GW/WG-mediated SGS3-AGO1 interaction facilitates siRNA amplification via RDR6 in plants.

molecular biology↗

bioRxiv2024

The Arabidopsis RNA-binding protein SGS3 is recruited to the chromatin remodeler CHR11 to promote siRNA production from protein-coding genes

In plants, aberrant RNAs produced by endogenous genes or transgenes are normally degraded by the nuclear and cytosolic RNA quality control (RQC) pathways. Under certain biotic or abiotic stresses, RQC is impaired, and aberrant RNAs are converted into siRNAs that initiate post-transcriptional gene silencing (PTGS) in the cytosol. How aberrant RNAs are selected and brought to the cytoplasm is not known. Here we show that the RNA-binding protein SUPPRESSOR OF GENE SILENCING (SGS)3 shuttles between the cytosol and the nucleus where it associates with the ISWI-like CHROMATIN REMODELER (CHR)11. CHR11 binds to transgenes prone to trigger PTGS. Knocking down CHR11 and its paralog CHR17 strongly reduces transgene PTGS, suggesting that SGS3 recruitment by CHR11/17 facilitates PTGS initiation. CHR11 is also enriched at endogenous protein-coding genes (PCGs) producing nat-siRNAs and va-siRNAs under biotic or abiotic stresses, and this production is reduced in chr11 chr17 double mutants at genome-wide level. Moreover, impairing CHR11 and CHR17 rescues the lethal phenotype caused by the massive production of siRNAs from PCGs in RQC-deficient mutants. We propose that SGS3 recruitment by CHR11/17 allows exporting RNAs to the cytosol to initiate the production of siRNAs. One Sentence SummaryThe plant PTGS component SGS3 is recruited by the chromatin remodeler CHR11 to select nuclear RNAs for export to the cytosol and siRNA production.

cell biology↗

bioRxiv2022

Synergistic action of the Arabidopsis spliceosome components PRP39a and SmD1 in promoting post-transcriptional transgene silencing

Besides regulating splicing, the conserved spliceosome component SmD1 was shown to promote posttranscriptional silencing of sense transgenes (S-PTGS). Here, we show that the conserved spliceosome component PRP39a also plays a role in S-PTGS. However, PRP39a and SmD1 actions appear distinct in both splicing and S-PTGS. Indeed, RNA-seq analysis of prp39a and smd1 mutants identified different sets of deregulated mRNAs and non-coding RNAs, both at expression level and alternative splicing genome-wide. Moreover, double mutant analyses involving prp39a or smd1 and RNA quality control (RQC) mutants revealed genetic interactions of SmD1 and PRP39a with distinct nuclear RQC machineries, suggesting synergistic rather than redundant roles in the RQC/PTGS interplay. Supporting this hypothesis, a prp39a smd1 double mutant exhibited enhanced suppression of S-PTGS compared with single mutants. Because no major changes in the expression of PTGS or RQC components or in small RNA production were identified in prp39a and smd1 mutants, and because prp39a and smd1 mutations do not alter PTGS triggered by inverted-repeat transgenes directly producing dsRNA (IR-PTGS), PRP39a and SmD1 seem to synergistically promote a step specific to S-PTGS. We propose that, independent of their specific roles in splicing, PRP39a and SmD1 limit 3-to-5 and 5-to-3 degradation of transgene aberrant RNAs, respectively, thus favoring the export of aberrant RNAs to the cytoplasm where their transformation into dsRNA initiates S-PTGS.

plant biology↗

bioRxiv2021

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

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 prefers the unloaded and 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, the non-degradable AGO1 protein assembles high molecular weight 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 role in quality control to avoid off-target cleavage.

cell biology↗