QTL mapping of a natural genetic polymorphism for long-term parasite persistence in<i>Daphnia</i>populations

Krebs, Michelle; Routtu, Jarkko; Ebert, Dieter

doi:10.1017/s0031182017001032

Cited by 15 publications

(24 citation statements)

References 51 publications

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“…To compare our findings to previous work we obtained the 95% confidence intervals of QTL identified 149 for other pathogens in D. magna (Routtu and Ebert 2015; Krebs et al 2017). As confidence intervals 150…”

Section: Comparison With Previous Studies 148mentioning

confidence: 86%

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Four QTL underlie resistance to a microsporidian parasite that may drive genome evolution in itsDaphniahost

Keller

Kirk

Luijckx

2019

Preprint

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11Despite its pivotal role in evolutionary and ecological processes the genetic architecture underlying host-12 parasite interactions remains understudied. Here we use a quantitative trait loci approach to identify 13 regions in the Daphnia magna genome that provide resistance against its microsporidium parasite 14Ordospora colligata. The probability that Daphnia became infected was affected by a single locus and an 15 interaction between two additional loci. A fourth locus influenced the number of spores that grew within 16 the host. Comparing our findings to previously published genetic work on Daphnia magna revealed that 17 two of these loci may be the same as detected for another microsporidium parasite, suggesting a general 18 immune response to this group of pathogens. More importantly, this comparison revealed that two regions 19 previously identified to be under selection coincided with parasite resistance loci, highlighting the pivotal 20 role parasites may play in shaping the host genome. 21

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Section: Comparison With Previous Studies 148mentioning

confidence: 86%

“…Hamiltosporidium may even be coded for by the same QTL (Routtu and Ebert 2015; Krebs et al 2017). 298…”

Section: Infectivity 165mentioning

confidence: 99%

Four QTL underlie resistance to a microsporidian parasite that may drive genome evolution in itsDaphniahost

Keller

Kirk

Luijckx

2019

Preprint

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“…As pond‐dwelling organisms offer ideal systems to study evolution at a microgeographic scale (they have clearly‐defined populations, and environmental factors can vary markedly between ponds, even at small spatial scales), we chose for this study the Holarctic‐distributed, cyclically parthenogenetic crustacean Daphnia magna and its microsporidian parasite Hamiltosporidium tvaerminnensis (Haag, Larsson, Refardt, & Ebert, ). Quantitative variation in resistance is common in this system and has been shown to have a genetic basis (Ebert, ; Krebs, Routtu, & Ebert, ; Routtu & Ebert, ). Evidence from experimental evolution in both natural and semi‐natural conditions indicates that H. tvaerminnensis has the potential to drive rapid changes in the genetic composition of host populations (Haag & Ebert, ; Zbinden, Haag, & Ebert, ) and that parasite‐mediated selection leads to rapid host adaptation to the parasite (Zbinden et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…As pond-dwelling organisms offer ideal systems to study evolution at a microgeographic scale (they have clearly-defined populations, and environmental factors can vary markedly between ponds, even at small spatial scales), we chose for this study the Holarctic-distributed, cyclically parthenogenetic crustacean Daphnia magna and its microsporidian parasite Hamiltosporidium tvaerminnensis (Haag, Larsson, Refardt, & Ebert, 2011). Quantitative variation in resistance is common in this system and has been shown to have a genetic basis (Ebert, 2008;Krebs, Routtu, & Ebert, 2017;Routtu & Ebert, 2015).…”

Section: Introductionmentioning

confidence: 99%

Parasite‐mediated selection in a natural metapopulation of Daphnia magna

et al. 2019

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Parasite‐mediated selection varying across time and space in metapopulations is expected to result in host local adaptation and the maintenance of genetic diversity in disease‐related traits. However, nonadaptive processes like migration and extinction‐(re)colonization dynamics might interfere with adaptive evolution. Understanding how adaptive and nonadaptive processes interact to shape genetic variability in life‐history and disease‐related traits can provide important insights into their evolution in subdivided populations. Here we investigate signatures of spatially fluctuating, parasite‐mediated selection in a natural metapopulation of Daphnia magna. Host genotypes from infected and uninfected populations were genotyped at microsatellite markers, and phenotyped for life‐history and disease traits in common garden experiments. Combining phenotypic and genotypic data a QST–FST‐like analysis was conducted to test for signatures of parasite mediated selection. We observed high variation within and among populations for phenotypic traits, but neither an indication of host local adaptation nor a cost of resistance. Infected populations have a higher gene diversity (Hs) than uninfected populations and Hs is strongly positively correlated with fitness. These results suggest a strong parasite effect on reducing population level inbreeding. We discuss how stochastic processes related to frequent extinction‐(re)colonization dynamics as well as host and parasite migration impede the evolution of resistance in the infected populations. We suggest that the genetic and phenotypic patterns of variation are a product of dynamic changes in the host gene pool caused by the interaction of colonization bottlenecks, inbreeding, immigration, hybrid vigor, rare host genotype advantage and parasitism. Our study highlights the effect of the parasite in ameliorating the negative fitness consequences caused by the high drift load in this metapopulation.

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“…In contrast, the subsequent components of a host's defence cascade (i.e., secondary lines of defence) are more likely to reflect multiple minor alleles and environmental influences. Here many different pathways contribute to the control of pathogen proliferation, such as the host immune system, the availability of resources that a pathogen might exploit, and the general vigour or quality of a host, giving rise to a continuous distribution of possible infection outcomes known as "quantitative resistance" (Corwin & Kliebenstein, 2017;Krebs, Routtu, & Ebert, 2017;de Nooij & van Damme, 1988;Poland, Balint-Kurti, Wisser, Pratt, & Nelson, 2009). A particular defence mechanism may not be completely effective, but instead relate to the ability to recover from infection or limit the deleterious fitness costs associated with the growth of a pathogen (see also tolerance; Råberg, Graham, & Read, 2009).…”

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confidence: 99%

Dissecting the genetic architecture of a stepwise infection process

2019

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How a host fights infection depends on an ordered sequence of steps, beginning with attempts to prevent a pathogen from establishing an infection, through to steps that mitigate a pathogen's control of host resources or minimize the damage caused during infection. Yet empirically characterizing the genetic basis of these steps remains challenging. Although each step is likely to have a unique genetic and environmental signature, and may therefore respond to selection in different ways, events that occur earlier in the infection process can mask or overwhelm the contributions of subsequent steps. In this study, we dissect the genetic architecture of a stepwise infection process using a quantitative trait locus (QTL) mapping approach. We control for variation at the first line of defence against a bacterial pathogen and expose downstream genetic variability related to the host's ability to mitigate the damage pathogens cause. In our model, the water‐flea Daphnia magna, we found a single major effect QTL, explaining 64% of the variance, that is linked to the host's ability to completely block pathogen entry by preventing their attachment to the host oesophagus; this is consistent with the detection of this locus in previous studies. In susceptible hosts allowing attachment, however, a further 23 QTLs, explaining between 5% and 16% of the variance, were mapped to traits related to the expression of disease. The general lack of pleiotropy and epistasis for traits related to the different stages of the infection process, together with the wide distribution of QTLs across the genome, highlights the modular nature of a host's defence portfolio, and the potential for each different step to evolve independently. We discuss how isolating the genetic basis of individual steps can help to resolve discussion over the genetic architecture of host resistance.

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QTL mapping of a natural genetic polymorphism for long-term parasite persistence inDaphniapopulations

Cited by 15 publications

References 51 publications

Four QTL underlie resistance to a microsporidian parasite that may drive genome evolution in itsDaphniahost

Four QTL underlie resistance to a microsporidian parasite that may drive genome evolution in itsDaphniahost

Parasite‐mediated selection in a natural metapopulation of Daphnia magna

Dissecting the genetic architecture of a stepwise infection process

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