Notwithstanding recent evidences, paternal environment is thought to be a potential but unlikely source of fitness variation that can affect trait evolution. Here we studied intergenerational effects of males’ exposure to varying adult density in Drosophila melanogasterlaboratory populations. We held sires at normal (N), medium (M) and high (H) adult densities for 2 days before allowing them to mate with virgin females. This treatment did not introduce selection through differential mortality. Further, we randomly paired males and females and allowed a single round of mating between the sires and the dams. We then collected eggs from the dams and measured the egg size. Finally, we investigated the effect of the paternal treatment on juvenile and adult (male) fitness components. We found a significant treatment effect on juvenile competitive ability where the progeny sired by the H‐males had higher competitive ability. Since we did not find the treatment to affect egg size, this effect is unlikely to be mediated through variation in female provisioning. Male fitness components were also found to have a significant treatment effect: M‐sons had lower dry weight at eclosion, higher mating latency, and lower competitive mating success. While being the first study to show both adaptive and non‐adaptive effect of the paternal density in Drosophila, our results highlight the importance of considering paternal environment as important source of fitness variation.
Evolutionary theory predicts a late-life decline in the force of natural selection, possibly leading to late-life deregulations of the immune system. A potential outcome of such deregulations is the inability to produce specific immunity against target pathogens. We tested this possibility by infecting multiple Drosophila melanogaster lines (with bacterial pathogens) across age groups, where either individual or different combinations of Imd- and Toll-inducible antimicrobial peptides (AMPs) were deleted using CRISPR gene editing. We show a high degree of non-redundancy and pathogen-specificity of AMPs in young flies: in some cases, even a single AMP could confer complete resistance. However, ageing led to drastic reductions in such specificity to target pathogens, warranting the action of multiple AMPs across Imd and Toll pathways. Moreover, use of diverse AMPs either lacked survival benefits or even accompanied survival costs post-infection. These features were also sexually dimorphic: females required a larger repertoire of AMPs than males but extracted equivalent survival benefits. Finally, age-specific expansion of the AMP-repertoire was accompanied with ageing-induced downregulation of negative-regulators of the Imd pathway and damage to renal function post-infection, as features of poorly regulated immunity. Overall, we could highlight the potentially non-adaptive role of ageing in producing less-specific AMP responses, across sexes and pathogens.
Evolutionary theory predicts late-life decline in the force of natural selection, which could lead to late-life deregulation of immune pathways with increased immunopathological effects. A potential outcome of such ageing-induced immune deregulation is the inability to produce specific immune responses against target pathogens. Instead, non-specific responses would produce an extended set of immune repertoires with little or no fitness benefits, or even increasing fitness costs. We tested this possibility by using two entomopathogens Providencia rettgeri and Pseudomonas entomophila to infect multiple Drosophila melanogaster lines with CRISPR/Cas9-induced knockout of either individual or different combinations of Imd and Toll-inducible antimicrobial peptides (AMPs). As expected, in young flies, AMPs showed a high degree of non-redundancy and pathogen-specificity such that in some cases even a single AMP could confer complete resistance. In contrast, ageing led to a complete loss of specificity, producing complex interactions between multiple AMPs across Toll and Imd pathways. Moreover, nonspecific responses using diverse AMPs with ageing either had no survival benefits, or imposed survival costs against P. rettgeri and P. entomophila. These features of immune senescence were also sexually dimorphic: females expressed a larger repertoire of AMPs compared to males but extracted equivalent survival benefits. Finally, age-specific expansion of the AMP pool was associated with several potential features of a poorly regulated immune system, such as downregulation of negative regulators of the Imd-pathway (e.g., caudal & pirk) and a trend of reduced renal function (i.e., Malpighian tubule activity), following infection, indicating the risk of increased immunopathological damage. Taken together, we demonstrate age-dependent changes in AMP specificity, and how this is associated with variation in immune senescence across sexes and pathogens.
Notwithstanding recent evidences, paternal environment is thought to be a potential but unlikely source of fitness variation that can affect trait evolution. Here we studied intergenerational effects of males’ exposure to varying adult density in Drosophila melanogasterlaboratory populations. We held sires at normal (N), medium (M) and high (H) adult densities for 2 days before allowing them to mate with virgin females. This treatment did not introduce selection through differential mortality. Further, we randomly paired males and females and allowed a single round of mating between the sires and the dams. We then collected eggs from the dams and measured the egg size. Finally, we investigated the effect of the paternal treatment on juvenile and adult (male) fitness components. We found a significant treatment effect on juvenile competitive ability where the progeny sired by the H‐males had higher competitive ability. Since we did not find the treatment to affect egg size, this effect is unlikely to be mediated through variation in female provisioning. Male fitness components were also found to have a significant treatment effect: M‐sons had lower dry weight at eclosion, higher mating latency, and lower competitive mating success. While being the first study to show both adaptive and non‐adaptive effect of the paternal density in Drosophila, our results highlight the importance of considering paternal environment as important source of fitness variation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.