Biology subjects

Merret, R.

Publications and source records attributed to Merret, R..

10 recordsLinked to original sources

bioRxiv2026

Dynamic 2'-O-Me of rRNA regulates ribosome translation in Arabidopsis nucleolin1 mutants and during seed-to-seedling transition

Across all kingdoms of life, 2'-O-ribose methylation (2'-O-Me) is the most abundant modification of ribosomal RNAs (rRNAs), which are central to ribosome assembly and function. The 2'-O-Me of specific rRNA sites is catalysed by C/D-box small nucleolar ribonucleoprotein (snoRNP) complexes. However, how and when the landscape of plant rRNA 2'-O-Me modifications is remodelled remains largely unexplored. To study the regulation of rRNA 2'-O-Me and its impact on ribosome translation, we characterised Arabidopsis NUCLEOLIN 1 (NUC1)-depleted plants, which exhibit reduced 2'-O-Me at dozens specific rRNA sites, and investigated the impact of 2'-O-Me in ribosome translation during plant development. We demonstrated that 2'-O-Me is dynamically regulated during seed-to-seedling transition. Our analysis identified differentially methylated rRNA sites, which are specifically located in structurally critical regions of the ribosome. Notably, this hypomethylation is uncoupled from the global expression, assembly, or subcellular localisation of C/D-box snoRNPs. We further observed that polysomes with low 2'-O-Me levels not only accumulate but also exhibit differential mRNA loading. These polysomes characterised by reduced 2'-O-Me at specific rRNA sites, influence multiples aspects of translation, including ribosomes stalling at the initiation, elongation and termination steps. Together, these findings advance our understanding of the dynamic regulation of rRNA 2'-O-methylation and its functional role in ribosome-mediated translation in plants.

plant biology↗

bioRxiv2026

Drying kinetics govern transcriptional and post-transcriptional reprogramming during seed maturation

Desiccation tolerance (DT) serves as a cornerstone for seed survival and for long-term persistence in the natural environment. DT is acquired during seed development, as seeds undergo a drastic change in internal water content during maturation drying. Although the physiological effects of drying on the acquisition of DT and other seed traits have been described, the molecular mechanisms underlying these effects have not yet been fully understood. Here, we addressed this gap by submitting maturing seeds of Arabidopsis thaliana L. to three different drying regimes - fast drying (FD), slow drying (SD), and a combination of both (SDFD) and studying physiological, transcriptional, and post-transcriptional responses. We found that SD not only accelerated DT acquisition but also seed maturation. Each drying regime showed a distinct transcriptional signature, with SD and SDFD showing greater global gene downregulation compared to FD. This downregulation appeared to be crucial for establishing DT in developing seeds. Interestingly, FD triggered a specific defense-related transcriptional response that was detrimental to seed longevity. Using an abscisic acid deficient mutant, we found that most of the drying-mediated transcriptional changes were largely independent of the wild-type ABA levels. On a post-transcriptional level, SD led to a major turnover of mRNA populations undergoing co-translational mRNA decay (CTRD) and promoted CTRD of stress-related genes. Overall, our study provides fundamental insights into the mechanisms by which seeds perceive and respond to drying, advancing our basic understanding of the molecular regulation of DT and seed maturation. Significance StatementSeed maturation is a critical phase of the plant life cycle when seeds acquire desiccation tolerance (DT) required for long-term storage. Drying rate, together with abscisic acid (ABA), has been implicated in this process, but whether seed development actively responds to different drying rates and how such responses are regulated has remained unclear. Here, we show that maturing seeds sense and respond to different drying regimes through distinct molecular programs, with slow drying triggering coordinated transcriptional and post-transcriptional reprogramming associated with enhanced DT. This response occurs partly independent of wild-type ABA levels, revealing drying rate as a developmental signal acting alongside hormonal regulation to direct seed maturation. These findings provide a framework for improving drying strategies and identifying molecular markers of seed quality.

plant biology↗

bioRxiv2025

Loss of tRNA uridine thiolation affects mRNA translation, protein production, and sulfur-compound metabolism in Arabidopsis

The uridine at position 34 of tRNA anticodon loops is always modified at variable levels depending on environmental conditions, but a function for this highly conserved modification has not been firmly established. Using Arabidopsis thaliana, we show that the thiolation of U34 is a prerequisite for the subsequent modifications at position 32 and 37 of the tRNALys(UUU) anticodon loop, revealing a novel modification network. Surprisingly, the level of tRNALys(UUU) is strongly increased rather than reduced in the ctu1 or ctu2 mutant backgrounds that prevent these modifications. This suggests the existence of a regulatory feedback loop that drives the transcription of this specific tRNA gene family. Furthermore, we observed that the ability of the ribosome to decode AAA, GAA and CAA codons is impaired when the thiol group is lost, leading to a reduction in protein production, especially for genes enriched in these codons. Finally, we show that loss of tRNA thiolation results in variations in levels of many proteins involved in sulfur-compound metabolism and several sulfur-containing metabolites, suggesting that the level of tRNA thiolation may act as a sensor that regulates these processes.

molecular biology↗

bioRxiv2024

Regulation of co-translational mRNA decay by PAP and DXO1 in Arabidopsis

BackgroundmRNA decay is central in the regulation of mRNA homeostasis in the cell. The recent discovery of a co-translational mRNA decay pathway (also called CTRD) has changed our understanding of the mRNA decay process. This pathway has emerged as an evolutionarily conversed mechanism essential for specific physiological processes in eukaryotes, especially in plants. In Arabidopsis, this pathway is targeted mainly by the exoribonuclease XRN4. However, the details of the molecular regulation of this pathway are still unclear. ResultsIn this study, we first tested the role of the 3'-phosphoadenosine 5'-phosphate (PAP), an inhibitor of exoribonucleases in the regulation of CTRD. Using 5Pseq approach, we discovered that FRY1 inactivation impaired XRN4-CTRD activity. Based on this finding, we demonstrated that exogenous PAP treatment stabilizes CTRD mRNA targets. Furthermore, we also tested the implication of the exoribonuclease DXO1 in CTRD regulation. We found that DXO1, another exoribonuclease sensitive to PAP, is also involved in the CTRD pathway, especially by targeting NAD+-capped mRNAs. DXO1 specifically targets mRNAs linked to stress response. ConclusionsOur study provides further insights into the regulation of CTRD in Arabidopsis and demonstrates that other exoribonucleases can be implicated in this pathway.

plant biology↗

bioRxiv2024

Genome-wide analysis of mRNA decay in Arabidopsis shoot and root reveals the importance of co-translational mRNA decay in the general mRNA turnover

Until recently, the general 5-3 mRNA decay was placed in the cytosol after the mRNA was released from ribosomes. However, the discovery of an additional 5 to 3 pathway, the Co-Translational mRNA Decay (CTRD), changed this paradigm. Up to date, defining the real contribution of CTRD in the general mRNA turnover has been hardly possible as the enzyme involved in this pathway is also involved in cytosolic decay. Here we overcame this obstacle and created an Arabidopsis line specifically impaired for CTRD called XRN4{Delta}CTRD. Through a genome-wide analysis of mRNA decay rate in shoot and root, we tested the importance of CTRD in mRNA turnover. First, we observed that mRNAs tend to be more stable in root than in shoot. Next, using XRN4{Delta}CTRD line, we demonstrated that CTRD is a major determinant in mRNA turnover. In shoot, the absence of CTRD leads to the stabilization of thousands of transcripts while in root its absence is highly compensated resulting in faster decay rates. We demonstrated that this faster decay rate is partially due to the XRN4-dependent cytosolic decay. Finally, we correlated this organ-specific effect with XRN4{Delta}CTRD line phenotypes revealing a crucial role of CTRD in mRNA homeostasis and proper organ development.

plant biology↗

bioRxiv2024

A multi-transcriptomics approach reveals the coordinated action of the endoribonuclease DNE1 and the decapping machinery in orchestrating mRNA decay

Decapping is a crucial step of mRNA degradation in eucaryotes and requires the formation of the holoenzyme complex between the decapping enzyme DCP2 and the decapping enhancer DCP1. In Arabidopsis, we recently identified DNE1, a NYN domain endoribonuclease, as a direct protein partner of DCP1. The function of both DNE1 and decapping are necessary to maintain phyllotaxis, the regularity of organ emergence in the apex. In this study we combined in vivo mRNA editing, RNA degradome, transcriptomics and small RNA-omics to identify targets of DNE1 and study how DNE1 and DCP2 cooperate in controlling mRNA fate. Our data reveal that DNE1 mainly contacts and cleaves mRNAs in the CDS and has sequence cleavage preferences. We found that DNE1 targets are also degraded through decapping, and that both RNA degradation pathways influence the production of mRNA-derived siRNAs. Finally, we detected mRNA features enriched in DNE1 targets including RNA G-quadruplexes and translated upstream-ORFs. Combining these four complementary high-throughput sequencing strategies greatly expands the range of DNE1 targets and allowed us to build a conceptual framework describing the influence of DNE1 and decapping on mRNA fate. These data will be crucial to unveil the specificity of DNE1 action and understand its importance for developmental patterning.

plant biology↗

bioRxiv2024

Plant response to intermittent heat stress involves modulation of mRNA translation efficiency

Acquired thermotolerance (also known as priming) is the ability of cells or organisms to better survive an acute heat stress if it is preceded by a milder one. In plants, acquired thermotolerance has been studied mainly at the transcriptional level, including recent descriptions of sophisticated regulatory circuits that are essential for this learning capacity. In this work, we tested the involvement of polysome-related processes (translation and cotranslational mRNA decay (CTRD)) in plant thermotolerance using two heat stress regimes with and without a priming event. We found that priming is essential to restore the general translational potential of plants shortly after acute heat stress. We observed that mRNAs not involved in heat stress suffer from a reduction in translation efficiency at high temperature, whereas heat stress-related mRNAs are translated more efficiently under the same condition. We also show that the induction of the unfolded protein response (UPR) pathway in acute heat stress is favoured by a previous priming event and that, in the absence of priming, ER-translated mRNAs become preferential targets of CTRD. Finally, we present evidence that CTRD can specifically regulate more than a thousand genes during heat stress and should be considered as an independent gene regulatory mechanism.

plant biology↗

bioRxiv2023

Cell type-specific control of secondary cell wall formation by Musashi-type translational regulators in Arabidopsis

Deciphering the mechanism of secondary cell wall/SCW formation in plants is key to understanding their development and the molecular basis of biomass recalcitrance. Although transcriptional regulation is essential for SCW formation, little is known about the implication of post-transcriptional mechanisms in this process. Here we report that two bonafide RNA-binding proteins homologous to the animal translational regulator Musashi, MSIL2 and MSIL4, function redundantly to control SCW formation in Arabidopsis. MSIL2/4 interactomes are similar and enriched in proteins involved in mRNA binding and translational regulation. MSIL2/4 mutations alter SCW formation in the fibers, leading to a reduction in lignin deposition, and an increase of 4-O-glucuronoxylan methylation. In accordance, quantitative proteomics of stems reveal an overaccumulation of glucuronoxylan biosynthetic machinery, including GXM3, in the msil2/4 mutant stem. We showed that MSIL4 immunoprecipitates GXM mRNAs, suggesting a novel aspect of SCW regulation, linking post-transcriptional control to the regulation of SCW biosynthesis genes.

plant biology↗

bioRxiv2022

High rates of spontaneous chromosomal duplications are compensated by translational regulation in a photosynthetic unicellular eukaryote

While duplications have long been recognized as a fundamental process driving major evolutionary innovations, direct estimations of spontaneous chromosome duplication rates, leading to aneuploid karyotypes, are scarce. Here, we provide the first estimations of spontaneous chromosome duplication rates in six unicellular eukaryotic species from mutation accumulation (MA) experiments. The spontaneous chromosome duplication rates reach 1x10-4 to 1x10-3 per genome per generation, which is ~4 to ~50 times less frequent than spontaneous point mutations per genome, whereas chromosome duplication events can affect 1 to 7% of the total genome size. Comparative transcriptomics between MA lines with different chromosome duplications reveals a strong positive correlation between RNA expression rate and DNA copy number. However, comparative analyses of the translation rate of mRNAs estimated by polysome profiling unravel a chromosome specific dosage compensation mechanism. In particular, one chromosome with a gene average of 2.1 excess of mRNAs is compensated by an average of ~0.7 decrease in translation rates. Altogether, our results are consistent with previous observations of a chromosome dependent effect of dosage compensation and provide evidence that it may occur during translation. These results support the existence of a yet unknown post-transcriptional mechanism orchestrating the modification of translation of hundreds of transcripts from genes located on duplicated regions in eukaryotes.

evolutionary biology↗

bioRxiv2021

RNA labelling in live plants reveals single cell transcriptional dynamics: application to phosphate signaling

Plants are sessile organisms constantly adapting to ambient fluctuations through spatial and temporal transcriptional responses. Here, we implemented the latest generation RNA imaging system and combined it with microfluidics to visualize transcriptional regulation in living Arabidopsis plants. This enabled quantitative measurements of the transcriptional activity of single loci in single cells, real time and changing environmental conditions. Using phosphate responsive genes as model, we found that active genes displayed high transcription initiation rates ([~]3s) and frequently clustered together in endoreplicated cells. We observed gene bursting and large allelic differences in single cells, revealing that at steady-state, intrinsic noise dominated extrinsic variations. Moreover, we established that transcriptional repression triggered in roots by phosphate, a crucial macronutrient limiting plant development, occurred with unexpected fast kinetics ([~]minutes) and striking heterogeneity between neighboring cells. Access to single cell RNA polymerase II dynamics within live plants will benefit future studies of signaling processes.

plant biology↗