Biology subjects

Vignolini, T.

Publications and source records attributed to Vignolini, T..

6 recordsLinked to original sources

bioRxiv2026

A variant rRNA serves as a translational repressor in Plasmodium falciparum

Ribosome composition can vary through differences in associated proteins, post-transcriptional and post-translational modifications. Such heterogeneity enables ribosomes to respond to environmental1 or pathological2,3 conditions, and modulate localized translation4. A long-standing observation has also been the differential expression of variant ribosomal RNA (rRNA) alleles across developmental5-7 or cellular states8-14. Yet how exchanging the catalytic ribosome core could regulate translational outcomes remains unknown. Here, we report the functional characterization of a genomically-encoded, divergent rRNA that serves as a dominant-negative repressor of translation during host-to-vector transmission in the human malaria parasite. This allele only encodes for large subunit rRNAs, lacks ITS2 splicing, yet retains conserved rRNA modification and folding patterns alongside vast expansion segments. The resulting large subunit engages mRNA at translation start sites but appears to elongate inefficiently, likely due to divergences in the peptidyl transferase center obstructing the exit tunnel. Through its precisely timed transcription immediately after transmission, this rRNA represses mRNAs that were highly translated in the human, facilitating the transition of the translational program for mosquito-stage development. Our data identify a repressive ribosome population whose antagonistic function is encoded by an independently evolved, variant rRNA allele, defining the conceptual foundation for an additional layer of inherent translational regulation.

molecular biology↗

bioRxiv2026

MaRNAV-1 infection of Plasmodium vivax is associated with increased parasite transmission and host inflammatory responses

MaRNAV-1 is an RNA virus recently identified in Plasmodium vivax-infected samples, but definitive evidence that it infects the parasite and influences malaria pathogenesis remains unknown. Here, we demonstrate that MaRNAV-1 is an intracellular virus that is present in P. vivax at various stages of its life cycle, including blood, sporozoite, and liver stages. Viral prevalence varied geographically between Cambodian and Ethiopian parasites. MaRNAV-1 presence and load were positively associated with parasite transmission potential, as reflected by increased gametocyte abundance and higher oocyst prevalence and intensity in membrane feeding assays. MaRNAV-1 loads were higher in symptomatic compared to asymptomatic infections, and higher MaRNAV-1 loads were associated with elevated body temperature, independently of parasitemia. MaRNAV-1 infection elicits an antibody response and is associated with dendritic cell activation, a shift from Th2 to a Th1-driven immune response, and an increased frequency of double-negative B cells. Accordingly, MaRNAV-1-infected patients had higher concentrations of circulating cytokines, such as IFN-{gamma}, CXCL10, IL-1RA, and IL-6, independently of parasitemia. Together, these findings demonstrate that MaRNAV-1 is a genuine parasite-infecting virus associated with increased parasite transmission potential and with modulation of clinical outcomes in, and host immune response to, P. vivax infections. Our study broadens the conventional view of host-pathogen interactions in malaria by revealing complex virus-parasite-host relationships.

microbiology↗

bioRxiv2025

N6-methyladenosine primes the malaria parasite for transmission

Sudden environmental changes are a recurring challenge for unicellular organisms, but a necessity for many to progress through their lifecycle. To transmit from its human host to mosquito vector, malaria parasites differentiate into male and female, semi-quiescent stages that can re-initiate development within seconds after transmission. Here, we identify the RNA modification N6-methyladenosine (m6A) as the mediator of a rapid, sex-specific, and temperature-sensitive mechanism to restructure protein synthesis during transmission. We find that male parasites maintain high levels of translation during their semi-quiescence that are rapidly repressed following mosquito uptake. This translational shutdown is essential for the continuation of male parasite development and depends on the m6A-binding protein YTH.2. We further show that m6A and YTH.2 are already present prior to transmission, but that their repressive interaction requires a temperature drop accompanying the exit from the human host. Hence, m6A appears to prime the parasite transcriptome and subsequently converts an environmental shift into a rapid translational response.

molecular biology↗

bioRxiv2025

A metabolism-chromatin axis promotes ribosome heterogeneity in the human malaria parasite

The transmission of the most virulent human malaria parasite, Plasmodium falciparum, relies on its survival in the contrasting environments of the human host and mosquito vector. One of the most fascinating adaptations to this lifestyle is the specific silencing of individual rDNA genes in the human host that are de-repressed following host-to-vector transmission. In this study, we defined the epigenetic signatures of rRNA transcription and found that rDNA silencing relies on aerobic glycolysis, the sole energy-generating pathway in the human host. We show that disruption of NAD+ regeneration during lactate fermentation promotes rDNA de-repression and identify the sirtuin histone deacetylase Sir2a as the mediator between fluctuating NAD+ levels and a functional transcriptional outcome. Hence, rDNA activation appears to be coupled to the metabolic state of the parasite as it transitions from aerobic glycolysis to mitochondrial respiration during host-to-vector transmission.

microbiology↗

bioRxiv2023

Optimization of highly inclined Illumination for diffraction-limited and super-resolution microscopy

In HILO microscopy, a highly inclined and laminated light sheet is used to illuminate the sample, thus drastically reducing background fluorescence in wide-field microscopy, but maintaining the simplicity of the use of a single objective for both illumination and detection. Although the technique has become widely popular, particularly in single-molecule and super-resolution microscopy, a limited understanding of how to finely shape the illumination beam and how this impact on the image quality complicates setting HILO to fit the experimental needs. In this work, we build up a simple and comprehensive guide to optimize the beam shape and alignment in HILO and to predict its performance in conventional fluorescence and super-resolution microscopy. We model the beam propagation through Gaussian optics and validate the model through far- and near-field experiments, thus characterizing the main geometrical features of the beam. Further, we fully quantify the impact of a progressive reduction of the inclined beam thickness on the image quality of both diffraction-limited and super-resolution images and we show that the most relevant impact is obtained by reducing the beam thickness to sub-cellular dimensions (< 3 m). Based on this, we present a simple optical solution to reduce the inclined beam thickness down to 2.6 m while keeping a field-of-view dimension suited for cell imaging and allowing an increase in the number of localizations in super-resolution imaging of up to 2.6 folds.

biophysics↗

bioRxiv2018

Creation and multi-omics characterization of a genomically hybrid strain in the nitrogen-fixing symbiotic bacterium Sinorhizobium meliloti

Many bacteria, often associated with eukaryotic hosts and of relevance for biotechnological applications, harbour a multipartite genome composed by more than one replicon. Biotechnologically relevant phenotypes are often encoded by genes residing on the secondary replicons. A synthetic biology approach to developing enhanced strains for biotechnological purposes could therefore involve merging pieces or entire replicons from multiple strains into a single genome. Here we report the creation of a genomic hybrid strain in a model multipartite genome species, the plant-symbiotic bacterium Sinorhizobium meliloti. In particular, we moved the secondary replicon pSymA (accounting for nearly 20% of total genome content) from a donor S. meliloti strain to an acceptor strain. The cis-hybrid strain was screened for a panel of complex phenotypes (carbon/nitrogen utilization phenotypes, intra- and extra-cellular metabolomes, symbiosis, and various microbiological tests). Additionally, metabolic network reconstruction and constraint-based modelling were employed for in silico prediction of metabolic flux reorganization. Phenotypes of the cis-hybrid strain were in good agreement with those of both parental strains. Interestingly, the symbiotic phenotype showed a marked cultivar-specific improvement with the cis-hybrid strains compared to both parental strains. These results provide a proof-of-principle for the feasibility of genome-wide replicon-based remodelling of bacterial strains for improved biotechnological applications in precision agriculture.

synthetic biology↗