Biology subjects

Legarda, E. G.

Publications and source records attributed to Legarda, E. G..

4 recordsLinked to original sources

bioRxiv2026

Orsay virus infection is associated with reduced locomotion and alters cue-dependent food choice in Caenorhabditis elegans

Behavioral responses are an important component of host defense; however, most evidence in Caenorhabditis elegans comes from bacterial pathogens. Here, we tested whether infection with Orsay virus (OrV) alters host dispersal and food choice and whether these responses involve the RNA-processing factor EOL-1. When measuring distance travelled over a certain period of time in control and infected wild-type animals, we observed that OrV infection was associated with lower locomotion. Moreover, when presenting infected and control animals with food choices, we observed that infected animals preferred OrV infected food sources only when the alternative was a pure food source, preferring a non-inoculated food source when both control and viral food sources contained a C. elegans filtrate. Moreover, loss of EOL-1 altered baseline locomotion and attenuated the infection-associated reduction detected in the earlier motility assay, while also modifying the food choice response, suggesting that eol-1 contributes to the motility and behavioral changes induced by OrV infection. Collectively, these results support an overall association between OrV infection and reduced host dispersal, whereas its effect on food choice depends on the sensory context. These findings extend infection-associated behavioral responses to a natural viral pathogen and identify eol-1 as a modulator of their expression.

microbiology↗

bioRxiv2025

Cosmic silence and viral noise: transcriptomic crosstalk in Caenorhabditis elegans under simulated space conditions

Spaceflight environments pose unique physiological challenges due to altered gravity and radia-tion exposure. To investigate how these abiotic stressors interact with viral infection, we analyzed the transcriptomic response of Caenorhabditis elegans acclimated to simulated microgravity ({micro}G) and below-background muon radiation flux (BBR), upon infection with Orsay virus (OrV). Using RNA-seq, we characterized gene expression profiles across single and combined stress condi-tions. Both {micro}G and BBR elicited distinct stress responses, including modulation of oxidative stress, lipid metabolism, and immune pathways. OrV infection alone induced robust transcrip-tional changes, but its impact was significantly attenuated when combined with either abiotic stress, suggesting antagonistic interactions. Notably, proviral genes such as drl-1, fat-7 and hipr-1 were downregulated under BBR and {micro}G, potentially impairing viral replication. Gene ontology analyses revealed enrichment in immune effectors, RNA metabolism, and proteostasis-related pathways, particularly under BBR. Viral load and RNA2/RNA1 ratios were reduced in both stress conditions, indicating a shift in viral replication dynamics. Moreover, genomic diversity and de-fective viral genome formation were differentially affected, with increased genetic diversity and structural variation under stress. These findings suggest that acclimation to off-Earth conditions primes the host for a dampened response to an acute viral infection, potentially through resource reallocation and transcriptional attenuation. This study provides transcriptomic insight into viral infection under space-relevant conditions, highlighting complex stress interactions and their im-plications for host-pathogen dynamics in extraterrestrial environments.

microbiology↗

bioRxiv2024

Microgravity and low muon radiation affect viral pathogenesis and physiology in Caenorhabditis elegans

Environmental conditions fundamentally shape host-pathogen interactions, yet how multiple extreme abiotic stressors combine to influence infection outcomes remains poorly understood. Organisms evolved under specific gravitational and radiation regimes; deviations from these conditions --whether in extreme terrestrial environments or beyond Earth-- may alter immune function and pathogen replication. In this study, we investigated the effects of reduced gravity and lowered muon flux on Orsay virus infection in the nematode Caenorhabditis elegans. We employed a fully factorial experimental design, examining how each factor, alone and in combination, influences physiological traits and viral load. While below-background radiation radically affected viral accumulation dynamics, reduced gravity had a minor effect. Both factors significantly impacted reproduction and morphology, with some effects magnified by viral infection. These results reveal how even partial modifications of Earth-like gravity and radiation levels can alter pathogen-host interactions. By integrating experimental observations with mathematical modeling, we show that these environmental stressors primarily affect prezygotic reproductive processes and modulate viral replication through distinct and sometimes antagonistic mechanisms. Although this work does not encompass the full complexity of space environments, where cosmic radiation includes high-energy protons and heavy ions, it provides insight into how adjustable models of reduced gravity and radiation can advance our understanding of biological adaptation beyond standard terrestrial conditions. IMPORTANCEUnderstanding how extreme environmental conditions affect host-pathogen interactions is critical both for safeguarding biological systems during spaceflight and for exploring fundamental principles of stress biology. This study demonstrates that reduced gravity and diminished muon radiation flux can significantly alter viral infection dynamics and host physiology in Caenorhabditis elegans. By integrating experimental data with mathematical modeling, we reveal that these abiotic stresses impact prezygotic reproductive processes and modulate viral replication in distinct and sometimes antagonistic ways. Our findings suggest that even partial deviations from Earth-like conditions can reshape infection outcomes and developmental trajectories, highlighting the need for deeper mechanistic insights into biological adaptation beyond terrestrial norms. These results have implications for space biosciences, evolutionary virology, radiation hormesis theory, and the design of countermeasures to preserve organismal health in extreme or non-terrestrial habitats.

microbiology↗

bioRxiv2023

Evidence for gene transfer between mycoviruses and their host: Curvulaviridae as a case study

Gene transfer between distinct evolutionary lineages has been recognized as a frequent event occurring between viruses and their hosts. This phenomenon has been studied to some extent in animal and plant viruses, not so much in the case of mycoviruses, for which the evolutionary origins of their proteins remain poorly understood. In this study, we have tested the hypothesis of a mosaic origin for mycoviruses genomes, with the RNA-dependent RNA-polymerase (RdRp) being of viral origin and the coat protein (CP) resulting from one or more transfer events from the host genome. Firstly, phylogenetic trees were constructed for the RdRps and the CPs from a selection of viruses to address for possible incongruent evolutionary histories. Moreover, a PSI-BLAST search using the CP sequences from the different mycovirus groups retrieved hypothetical proteins (HP) with many orthologues in fungal genomes showing significant sequence homology with the CP from the members within the Curvulaviridae family. The structures of these HPs, predicted in silico using AlphaFold, tend to show high similarity with viral CPs suggesting the occurrence of gene transfer between viruses and fungi, although no clear function has been yet attributed to these genes in the host. Phylogenetic analyses suggest that this gene transfer could have occurred in multiple independent events. Additional selection analysis supports the notion that the most parsimonious explanation is the transfer of the HP from the host to an ancestral viral genome followed by fast evolution to accommodate the newly acquired protein to function as a CP.

microbiology↗