Biology subjects

Sucena, E.

Publications and source records attributed to Sucena, E..

6 recordsLinked to original sources

bioRxiv2025

Pathogen-Induced Damage in Drosophila: Uncoupling Disease Tolerance from Resistance

Immune response against infections can be divided into mechanisms of resistance that ensure active pathogen elimination, and mechanisms of disease tolerance, which include processes that return the host to physiological homeostasis without involving direct pathogen control. Studies on host immune responses to infection have mostly targeted mechanisms of resistance, and consequently, these are now well-described in both vertebrates and invertebrates. By comparison, the mechanistic basis of disease tolerance is less well understood. This is in part because both processes interact and can be difficult to separate under an infection scenario. Using the highly tractable insect model Drosophila melanogaster exposed to its natural entomopathogen, Pseudomonas entomophila, we aimed to tease apart mechanisms of disease tolerance from those of resistance. To this aim, we reasoned that oral exposure to heat-killed entomopathogenic bacteria should require disease tolerance without relying on resistance. Using this method, we observe that oral exposure to heat-killed P. entomophila causes mortality and reduced fecundity in D. melanogaster. We confirm that this reduction in fitness-related traits depends on the duration of the exposure, is sexually dimorphic, and is dependent on the virulence of the bacterium. We also found the microbiota to play a role, with its presence exacerbating the deleterious effect on host survival. This experimental framework, which may be extended to other systems, can be instrumental towards an understanding of the molecular, genetic, and physiological basis of disease tolerance and its interactions with resistance mechanisms.

immunology↗

bioRxiv2023

Adaptation to oral infection in D. melanogaster through evolution of both resistance and disease tolerance mechanisms

Pathogens exert strong selection on hosts, that evolve and deploy different defensive strategies, namely minimizing pathogen exposure (avoidance), directly promoting pathogen elimination (resistance), and/or managing the deleterious effects of illness (disease tolerance). However, how the response to pathogens partitions across these processes has never been directly assessed in a single system, let alone in the context of known adaptive trajectories under controlled selection regimes. Here, an experimental evolution system composed of D. melanogaster and its natural pathogen P. entomophila is used to independently assess the role of behavioural traits, and of resistance and disease tolerance mechanisms on host evolution. We compare one replicate of a population adapted to oral infection with P. entomophila (BactOral) to a replicate of its control population to find no evidence for behavioural change but measurable differences in both resistance and disease tolerance. In BactOral, we identify a relative decrease in bacterial loads correlated with an increase in gut production of specific AMPs, but no differences in bacterial intake, in gut cell renewal rate, or in the rate of bacterial defecation, pointing to a strengthening in resistance. Additionally, we posit that disease tolerance also contributes to the adaptive response of the BactOral population through a tighter control of its immune response and of the deleterious effects of exposure. This study reveals a genetically complex and mechanistically multi-layered response, possibly reflecting the structure of adaptation to infection in natural populations.

evolutionary biology↗

bioRxiv2021

Co-option of local and systemic immune responses by the hormonal signalling system triggering metamorphosis

Insect metamorphosis is regulated by the production, secretion and degradation of two peripheral hormones: 20-hydroxyecdysone (ecdysone) and juvenile hormone (JH). In addition to their roles in developmental regulation, increasing evidence suggests that these hormones are involved in innate immunity processes, such as phagocytosis and the induction of antimicrobial peptide (AMP) production. AMP regulation includes systemic responses as well as local responses at surface epithelia that contact with the external environment. At pupariation, Drosophila melanogaster increases dramatically the expression of three AMP genes, drosomycin (drs), drosomycin-like 2 (drsl2) and drosomycin-like 5 (drsl5). We show that the systemic action of drs at pupariation is dependent on ecdysone signalling in the fat body and operates via the ecdysone downstream target, Broad-Z4. In parallel, ecdysone also regulates local responses, specifically through the activation of drsl2 expression in the gut. Finally, we confirm the relevance of this ecdysone dependent AMP expression for the control of bacterial persistence by showing that flies lacking drs expression in the fat body have higher bacterial persistence over metamorphosis. Together, our data emphasize the importance of the association between ecdysone signalling and immunity using in vivo studies and establish a new role for ecdysone at pupariation, which impacts developmental success by regulating the immune system in a stage-dependent manner. We speculate that this co-option of immune effectors by the hormonal system may constitute a pre-emptive mechanism to control bacterial numbers in the pupa at the core of metamorphosis evolution.

developmental biology↗

bioRxiv2020

Wolbachia and host intrinsic reproductive barriers contribute additively to post-mating isolation in spider mites

AO_SCPLOWBSTRACTC_SCPLOWWolbachia are widespread maternally-inherited bacteria suggested to play a role in arthropod host speciation through induction of cytoplasmic incompatibility, but this hypothesis remains controversial. Most studies addressing Wolbachia-induced incompatibilities concern closely-related populations, which are intrinsically compatible. Here, we used three populations of two genetically differentiated colour forms of the haplodiploid spider mite Tetranychus urticae to dissect the interaction between Wolbachia-induced and host-associated incompatibilities, and to assess their relative contribution to post-mating isolation. We found that these two sources of incompatibility act through different mechanisms in an additive fashion. Host-associated incompatibility contributes 1.5 times more than Wolbachia-induced incompatibility in reducing hybrid production, the former through an overproduction of haploid sons at the expense of diploid daugters (ca. 75% decrease) and the latter by increasing the embryonic mortality of daughters (by ca. 49%). Furthermore, regardless of cross direction, we observed near-complete F1 hybrid sterility and complete F2 hybrid breakdown between populations of the two forms, but that Wolbachia did not contribute to this outcome. This study identifies the mechanistic independence and additive nature of host-intrinsic and Wolbachia-induced sources of isolation. It suggests that Wolbachia could drive reproductive isolation in this system, thereby potentially affecting host differentiation and distribution in the field.

evolutionary biology↗

bioRxiv2018

Spider mites escape bacterial infection by avoiding contaminated food

To fight infection, arthropods rely on the deployment of an innate immune response but also upon physical/chemical barriers and avoidance behaviours. However, most studies focus on immunity, with other defensive mechanisms being relatively overlooked.\n\nWe have previously shown that the spider mite Tetranychus urticae does not mount an induced immune response towards systemic bacterial infections, entailing very high mortality rates. Therefore, we hypothesized that other defence mechanisms may be operating to minimize infection risk. Here, we test (a) if spider mites are also highly susceptible to other infection routes - spraying and feeding - and (b) if they display avoidance behaviours towards infected food. Individuals sprayed with or fed on Escherichia coli or Pseudomonas putida survived less than the control, pointing to a deficient capacity of the gut epithelium, and possibly of the cuticle, to contain bacteria. Additionally, we found that spider mites prefer uninfected food to food contaminated with bacteria, a choice that probably does not rely on olfactory cues.\n\nOur results suggest that spider mites may rely mostly on avoidance behaviours to minimize bacterial infection and highlight the multi-layered nature of immune strategies present in arthropods.

ecology↗

bioRxiv2018

Genomic analysis of European Drosophila melanogaster populations on a dense spatial scale reveals longitudinal population structure and continent-wide selection

Genetic variation is the fuel of evolution, with standing genetic variation especially important for short-term evolution and local adaptation. To date, studies of spatio-temporal patterns of genetic variation in natural populations have been challenging, as comprehensive sampling is logistically difficult, and sequencing of entire populations costly. Here, we address these issues using a collaborative approach, sequencing 48 pooled population samples from 32 locations, and perform the first continent-wide genomic analysis of genetic variation in European Drosophila melanogaster. Our analyses uncover longitudinal population structure, provide evidence for continent-wide selective sweeps, identify candidate genes for local climate adaptation, and document clines in chromosomal inversion and transposable element frequencies. We also characterise variation among populations in the composition of the fly microbiome, and identify five new DNA viruses in our samples.

evolutionary biology↗