Biology subjects

Gattis, S.

Publications and source records attributed to Gattis, S..

3 recordsLinked to original sources

bioRxiv2025

Transcriptomic landscape reveals immunity related trade-offs in an invertebrate-fungal host-parasite system

O_LIBy exploiting host resources, parasites impose significant fitness costs onto their hosts, thereby affecting their population dynamics. Hosts, in turn, employ a series of mechanism to resist or tolerate parasitic infections. Unlike vertebrates, which possess a sophisticated immune system, invertebrates rely solely on innate immunity to combat pathogens. Despite over 50 years of research, the molecular basis of innate immunity in non-insect invertebrates remains limited. C_LIO_LIWe used the Daphnia magna - Metschnikowia bicuspidata host-parasite system to shed light on conserved immune responses among Daphnia species and parasite-driven immunological shifts. We examined the transcriptomic landscape across infected, exposed-uninfected and unexposed individuals and identified candidate genes that might be involved in the haemocyte recruitment. Additionally, we identified genes that might encode for reinforcement of the gut epithelium, and thus confer resistance to the parasite. C_LIO_LIWe measured life-history traits and observed that shifts correlated with immune activation. Specifically, exposed-uninfected individuals exhibited a delay in reproductive maturation, likely a direct effect of immune activation. However, these shifts appeared temporal, as animals compensated in total reproductive output over time. C_LIO_LIUnlike exposed-uninfected animals, infected individuals exhibited metabolic shifts that are indicative of host metabolic exhaustion. This metabolic reallocation aligns with the terminal investment hypothesis, where hosts facing high mortality risk divert resources from somatic maintenance to immediate reproduction in order to maximize fitness before death. C_LIO_LIOur findings provide novel insights into the molecular and physiological mechanisms underlying invertebrate immune responses and life-history trade-offs in the context of parasitic infections. C_LI

evolutionary biology↗

bioRxiv2025

Decoding host responses: How a freshwater invertebrate defends against a parasitic bacterium

Host-parasite interactions drive coevolutionary dynamics, often leading to reciprocal adaptations between hosts and parasites, a process known as the Red Queen arms race. While the molecular mechanisms underlying vertebrate and insect immune responses have been studied extensively, those of aquatic invertebrates remain unexplored, despite their critical role in ecosystem stability and aquaculture. Here, we use the Daphnia magna-Pasteuria ramosa system to investigate the hosts immune response and the molecular mechanisms underlying host-parasite interactions. We inoculated 800 D. magna hosts with 20,000 mature spores of P. ramosa and tracked the progression of infection by measuring the proportion of infected individuals and the developmental stages of the parasite at multiple time points post-inoculation (hereafter p.i.). RNA sequencing was performed at key infection phases, early (Cauliflower stage), mid (Cauliflower and Grape stages), and terminal (Cauliflower, Grape, and Mature spore stages), to capture gene expression changes linked to infection dynamics. Our transcriptomic analyses revealed key immune genes involved in host defense, including genes involved in Toll signaling pathways, thereby revealing significant changes in pathways related to immune function, host metabolism, and resource allocation. Our findings suggest that iron sequestration may serve as a host defense strategy to restrict parasite growth, representing a form of nutritional immunity. Furthermore, pathways associated with infection-induced phenotypic traits, such as somatic growth, red coloration, and castration, were significantly upregulated, underscoring the impact of the infection on host physiology. Taken together, these findings provide new insights into the interplay between hosts and parasites at a molecular level in an ecologically relevant system, advancing our understanding of infection strategies in aquatic invertebrates.

evolutionary biology↗

bioRxiv2024

Genetic basis of resistance in hosts facing alternative infection strategies by a virulent bacterial pathogen

Having alternative infection routes is thought to help parasites circumvent host resistance, provided that these routes are associated with different host resistance loci. This study examines whether alternate infection routes of the parasite Pasteuria ramosa are linked to distinct resistance loci in its crustacean host, Daphnia magna. We focus on the P. ramosa isolate P15, which can attach and penetrate the host through either the hindgut or the foregut. Using a global panel of 174 D. magna genotypes supplemented with breeding experiments, we analyzed resistance patterns for each of these infection routes. Our findings confirm our hypothesis: in D. magna, hindgut attachment is determined by the D locus, while foregut attachment is controlled by a newly identified G locus. We established a gene model for the G locus that indicated Mendelian segregation and epistatic interaction with at least one other resistance locus for P. ramosa, the C locus. Using genomic Pool-sequencing data, we localized the G locus within a known Pasteuria Resistance Complex on chromosome 4 of D. magna, whereas the D locus is on chromosome 7. Two candidate genes for the G locus, belonging to the Glycosyltransferase gene family, were identified. Our study sheds new light on host-parasite coevolution and enhances our understanding of how parasites evolve infection strategies. Author summaryParasites continuously evolve strategies to overcome host resistance, including the use of alternative infection routes. However, this strategy is advantageous only if host resistance loci are specific to each entry point; otherwise, a single host gene could provide resistance to all infection routes. In this study, we tested this hypothesis using the freshwater crustacean Daphnia magna and a strain of the parasite Pasteuria ramosa that can infect its host via the esophagus (foregut) or the hindgut. By conducting a phenotypic assay of P. ramosa attachment on a global panel of D. magna genotypes, we demonstrate that foregut and hindgut infections are associated with independent genetic host resistance loci. Through a breeding experiment on a subset of D. magna genotypes, we were able to propose a gene model for the newly discovered G locus linked to foregut attachment, while the previously identified D locus is linked to hindgut attachment. We also discovered that the foregut infection route is influenced by an epistatic interaction between the G locus and another P. ramosa resistance locus, the C locus. Using genomic data, we confirmed that the G and D loci are not overlapping, with the G locus being part of the Pasteuria Resistance Complex on chromosome 4, whereas the D locus is on chromosome 7. Two potential genes involved in glycosylation processes were identified as candidates for the G locus. Overall, our study confirms a key postulate in the understanding of host-parasite co-evolution, highlighting the importance of infection strategies in host resistance.

evolutionary biology↗