Biology subjects

Lecampion, C.

Publications and source records attributed to Lecampion, C..

8 recordsLinked to original sources

bioRxiv2025

Guanosine tetraphosphate (ppGpp) signalling promotes high-light tolerance in Arabidopsis thaliana.

Guanosine tetraphosphate (ppGpp) is a hyperphosphorylated nucleotide originally discovered in prokaryotes and found in the chloroplasts of plants and algae. In plants, ppGpp signalling plays a role as a regulator of photosynthetic activity, which is important in acclimation to environmental stresses such as nitrogen limitation. However, the full range of stresses involving ppGpp signalling is not yet known. Here, we investigated the role of ppGpp accumulation in the acclimation of plants to high light. We found that the over-accumulation of ppGpp in transgenic lines that overexpress RSH3 (OX:RSH3) increases tolerance to high light intensity. Although ppGpp leads to higher non-photochemical energy dissipation (NPQ) than in wild-type plants, we show that NPQ is not critical for the enhanced high-light tolerance. Rather, our results show that ppGpp accumulation leads to broad changes in plant physiology that prime plants to resist and subsequently recover from high light exposure. ppGpp levels themselves also increase in response to high light exposure, suggesting that ppGpp signalling may play a physiological role in high light acclimation. Our work highlights the importance of ppGpp signalling in plant stress acclimation.

plant biology↗

bioRxiv2023

Molecular crosstalk between plant translation initiation complexes influences the outcome of virus infection

Successful subversion of translation initiation factors 4E and 4G determines the infection success of potyviruses, the largest group of viruses affecting plants. In the natural variability of many plant species, resistance to potyvirus infection is provided by polymorphisms at 4E and 4G that renders them inadequate for virus hijacking but still functional in translation initiation. In crops where such natural resistance alleles are limited, the genetic inactivation of 4E has been proposed for the engineering of potyvirus resistance. However, recent findings indicate that knockout 4E and 4G alleles may be deleterious for plant health and could jeopardize resistance efficiency in comparison to functional resistance proteins. Here, we explored the cause of these adverse effects by studying the role of the Arabidopsis eIF4E1, whose inactivation was previously reported as conferring resistance to the potyvirus clover yellow vein virus (ClYVV) while also promoting susceptibility to another potyvirus called turnip mosaic virus (TuMV). We report that eIF4E1 is required to maintain global plant translation and to restrict TuMV accumulation during infection, and its absence is associated with a favoured virus multiplication over host translation. Furthermore, our findings demonstrate that eIF4E1 plays a crucial role in inhibiting the TuMV-induced degradation of the translation initiation factor eIFiso4G1, thereby preventing the generation of a truncated protein. Finally, we demonstrate a role for eIFiso4G1 in TuMV accumulation and in supporting plant fitness during infection. These findings suggest that eIF4E1 counteracts the hijacking of the plant translational apparatus during TuMV infection and underscore the importance of preserving the functionality of translation initiation factors 4E and 4G when implementing potyvirus resistance strategies. Author summaryPlants are constantly under threat from viruses that can damage crops and reduce yield. Among these viruses, potyviruses are a major concern, and a small group of genes known as eIF4E are key factors in making a plant susceptible to them. To combat these viruses, it is possible to either use naturally-selected variants of eIF4E that provide resistance, or to disable the gene altogether. However, new research has shown that inactivating eIF4E genes may have unintended consequences for the plants development while compromise resistance to other potyviruses. To investigate this further, we focus in this work on the role of the Arabidopsis eIF4E1 whose inactivation confers resistance to one potyvirus, clover yellow vein virus (ClYVV). We looked why this same mutation at eIF4E1 makes the plants more susceptible to another potyvirus, turnip mosaic virus (TuMV). Our study reveals that eIF4E1 acts in safeguarding the plant translational machinery during TuMV infection. By preventing the degradation of the translation initiation protein eIFiso4G1, eIF4E1 enables the plant to maintain its normal translation activity and ultimately prevents the accumulation of virus proteins. Our findings provide valuable insights into how potyviruses hijack the plants translation process, and emphasizes the need of preserving the functionality of translation initiation factors when developing potyvirus resistances.

plant biology↗

bioRxiv2023

Insights into the function of the chloroplastic ribosome-associated GTPase HflX in Arabidopsis thaliana.

Ribosome-associated GTPases are conserved enzymes that participate in ribosome biogenesis and ribosome function. In bacteria, recent studies have identified HflX as a ribosome-associated GTPase that is involved in both ribosome biogenesis and recycling under stress conditions. Plants possess a chloroplastic HflX homolog, but its function remains unknown. Here, we characterised the role of HflX in the plant Arabidopsis thaliana. Our findings demonstrate that HflX does not have a detectable role in plant growth and development, nor does it play a distinct role in acclimation to several different stresses, including heat, manganese, cold, and salt stress. However, we found that HflX is required for plant resistance to chloroplast translational stress mediated by the antibiotic lincomycin. Our results suggest that HflX is a chloroplast ribosome-associated protein that may play a role in the surveillance of translation. These findings provide new insight into the function of HflX as a ribosome-associated GTPase in plants and highlight the importance of investigating conserved proteins in different organisms to gain a comprehensive understanding of their biological roles.

plant biology↗

bioRxiv2023

Proteomic analyses of the Arabidopsis cap-binding complex define core set and TOR-dependent protein components

The eukaryotic cap-binding complex (CBC) is a hub for regulations affecting mRNA behaviour including translation, degradation and storage. Beside the core eukaryotic translation initiation factors, other proteins, many of which are yet unknown, are thought to interact stably or transiently with the CBC depending on cell status. The prototype of these regulators is the animal eIF4E binding protein (4E-BP), a direct target of the TOR (Target of Rapamycin) kinase that competes with the cap-binding protein eIF4E, thus repressing translation. In plants, no functional homologs of 4E-BP have so far been characterized. In this work we performed several deep proteomic analyses of the Arabidopsis CBC after cap-affinity purification from wild-type plants. We also investigated the CBC in eIF4E mutant plants, Arabidopsis lines with lower TOR activity, or during infection with eIF4E-dependent potyviruses, conditions which are all affecting translation at the initiation level. These analyses allowed us to define a limited core set of CBC components, which were detected in all samples. Interestingly, we identified proteins, like AGO1 or VCS, which were always detected in conditions where either TOR or mRNA translation were reduced. Meta-analysis of these data revealed several new plant interactors of the CBC, potentially defining pathways related to mRNA stability and degradation, metabolism and viral life cycle. A search for eIF4E binding motifs identified several new potential 4E-BP relatives in plants.

plant biology↗

bioRxiv2022

Structural Maintenance of Chromosome 3 interacts with the Topoisomerase VI complex and contributes to the oxidative stress response in Arabidopsis thaliana.

In plants adverse environmental conditions can induce the accumulation of reactive oxygen species, such as singlet oxygen or hydrogen peroxide, at the level of the photosynthetic apparatus. The coordinated action of nucleus-encoded genes is required for containing the deleterious effects of reactive oxygen species. The regulation of such genes follows a molecular signalling process between the chloroplast and the nucleus called retrograde signalling. Previously, we proposed that the Topoisomerase VI (Topo VI) complex participates in the singlet oxygen stress response by regulating the expression of specific subsets of nuclear genes. However, the underlying molecular mechanisms remain unresolved. In this study, we demonstrate that the Topo VI subunit BIN4 interacts with the cohesin subunit AtSMC3. We also show that, similarly to Topo VI mutants, a line suppressing AtSMC3 shows constitutive activation of singlet oxygen response genes and enhanced tolerance to photooxidative stress. Together, these results suggest that Topo VI and AtSMC3 control the expression of singlet oxygen response genes and are possibly involved in the acclimation of plants to photooxidative stress conditions.

plant biology↗

bioRxiv2022

TFIIF interacts with the Topoisomerase VI complex and selectively controls the expression of genes encoding PPR proteins involved in organellar RNA editing in Arabidopsis.

Communication between organelles and the nucleus is referred to as anterograde (nucleus to organelle) and retrograde (organelle to nucleus) signalling. In plants, the pentatricopeptide repeat (PPR) proteins represent a large family of nuclear-encoded proteins that are required for post-transcriptional control of chloroplast and mitochondria gene expression, and hence play a central role in the nuclear anterograde control of organelle genome expression. How PPR gene expression is controlled and regulated by retrograde signals is, however, still unknown. Here, we report a significant role for the general transcription factor TFIIF -subunit (TFIIF) in controlling PPR gene expression in Arabidopsis. First, we found that TFIIF interacts with the BIN4 subunit of the Topoisomerase VI (Topo VI). Transcriptome analysis of TFIIF and Topo VI mutant lines then revealed that many PLS-type PPR genes involved in RNA editing are reciprocally controlled by TFIIF and Topo VI. The misexpression of CLB19 and DYW1 genes in two allelic tfIIf mutants was associated with editing impairments in their plastid target RNAs rpoA and ndhD, respectively. Interestingly, we also detected a change in NDH activity in tfIIf plants. We also show that TFIIF and Topo VI coordinate the expression of NDH subunits encoded by the nuclear and plastid genomes. These results reveal the crucial role of the nuclear TFIIF and Topo VI complexes in controlling plastid genome expression at multiple levels of regulation, including the particular regulation of PPR gene expression.

plant biology↗

bioRxiv2021

A ppGpp-mediated brake on photosynthesis is required for acclimation to nitrogen limitation in Arabidopsis.

Guanosine pentaphosphate and tetraphosphate (together referred to as ppGpp) are hyperphosphorylated nucleotides found in bacteria and the chloroplasts of plants and algae. In plants and algae artificial ppGpp accumulation can inhibit chloroplast gene expression, and influence photosynthesis, nutrient remobilisation, growth, and immunity. However, it is so far unknown whether ppGpp is required for abiotic stress acclimation in plants. Here, we demonstrate that ppGpp biosynthesis is necessary for acclimation to nitrogen starvation in Arabidopsis. We show that ppGpp is required for remodeling the photosynthetic electron transport chain to downregulate photosynthetic activity and for protection against oxidative stress. Furthermore, we demonstrate that ppGpp is required for coupling chloroplastic and nuclear gene expression during nitrogen starvation. Altogether, our work indicates that ppGpp is a pivotal regulator of chloroplast activity for stress acclimation in plants.

plant biology↗

bioRxiv2019

Topoisomerase VI participates in an insulator-like function that prevents H3K9me2 spreading into euchromatic islands

The organization of the genome into transcriptionally active and inactive chromatin domains requires well-delineated chromatin boundaries and insulator functions in order to maintain the identity of adjacent genomic loci with antagonistic chromatin marks and functionality. In plants that lack known chromatin insulators, the mechanisms that prevent heterochromatin spreading into euchromatin remain to be identified. Here, we show that DNA Topoisomerase VI participates in a chromatin boundary function that safeguards the expression of genes in euchromatin islands within silenced heterochromatin regions. While some transposable elements are reactivated in mutants of the Topoisomerase VI complex, genes insulated in euchromatin islands within heterochromatic regions of the Arabidopsis thaliana genome are specifically downregulated. H3K9me2 levels consistently increase at euchromatin island loci and decrease at some TE loci. We further show that Topoisomerase VI physically interacts with S-adenosylmethionine (SAM) synthase MAT3, which is required for H3K9me2 deposition. Topoisomerase VI promotes MAT3 occupancy on heterochromatic elements and its exclusion from euchromatic islands, thereby providing a mechanistic insight into the essential role of Topoisomerase VI in the delimitation of chromatin domains.

plant biology↗