Intraspecific genetic variation in host vigour, viral load and disease tolerance during Drosophila C virus infection

Abstract

Genetic variation for resistance and disease tolerance has been described in a range of species. In Drosophila melanogaster , genetic variation in mortality following systemic Drosophila C virus (DCV) infection is driven by large-effect polymorphisms in the restriction factor pastrel (pst) . However, it is unclear if pst contributes to disease tolerance. We investigated systemic DCV challenges spanning nine orders of magnitude, in males and females of 10 Drosophila Genetic Reference Panel lines carrying either a susceptible (S) or resistant (R) pst allele. We find among-line variation in fly survival, viral load and disease tolerance measured both as the ability to maintain survival (mortality tolerance) and reproduction (fecundity tolerance). We further uncover novel effects of pst on host vigour, as flies carrying the R allele exhibited higher survival and fecundity even in the absence of infection. Finally, we found significant genetic variation in the expression of the JAK-STAT ligand upd3 and the epigenetic regulator of JAK-STAT G9a. However, while G9a has been previously shown to mediate tolerance of DCV infection, we found no correlation between the expression of either upd3 or G9a on fly tolerance or resistance. Our work highlights the importance of both resistance and tolerance in viral defence.

Effects of spontaneous mutations on survival and reproduction ofDrosophila serratainfected with Drosophila C virus

“…High perceived risk of extrinsic mortality (including due to disease) is predicted to select for higher investment in current reproduction (Hirshfield and Tinkle 1975; Corbel and Carazo 2022). Several studies in D. melanogaster have provided evidence that sub-lethal infection with DCV increases productivity (Gupta et al 2017; Kutzer et al 2023). Within the context of our experiment, the lower reproductive output of the high LT50 lines resulted in low relative fitness, despite their longer survival time.…”

Genetic variation in trophic avoidance shows fruit flies are generally attracted to bacterial pathogens

“…The ability to avoid contact with pathogens allows healthy individuals to evade the pathology resulting from infection and further prevents the activation of the immune response, which may be metabolically costly or even cause immunopathology, with detrimental effects on host fitness [27][28][29]. Given that individuals vary widely in susceptibility and in the extent to which they experience losses in fitness during infection [30][31][32][33], the potential costs and benefits of avoiding infection are therefore likely to vary between individuals [2,17]. Such variable costs, in turn, may contribute to the maintenance of standing genetic variation in avoidance via fluctuating selection [34][35][36], and affect the predicted evolutionary trajectories of pathogens [37,38].…”

Resource Quality Differentially Impacts Daphnia Interactions with Two Parasites

“…There is often substantial variation within species in susceptibility to infection; host genotype often strongly influences susceptibility due to a variety of factors, including variation in cellular immunity and barrier defenses (e.g., Leitão et al 2019, Cáceres andStewart Merrill 2023). Similarly, susceptible host genotypes can vary in their quality for the parasite, with parasites able to produce more infectious propagules in certain host genotypes (e.g., Auld et al 2017, Kutzer et al 2023. Additionally, host genotypes can vary in their sensitivity to changing resource quality, with variation in tolerance of low resource quality, and, conversely, in ability to exploit rich resource environments (e.g., Watt 1986, Hall et al 2012).…”